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From: [e-mail] (Chris Lewis)
Newsgroups: misc.consumers.house,rec.woodworking,news.answers
Subject: Electrical Wiring FAQ
Summary: A series of questions and answers about house wiring
Message-ID: <wirefaq_724656078@ecicrl>
Date: 18 Dec 92 05:21:34 GMT
Expires: 15 Jan 93 05:21:18 GMT
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Archive-name: electrical-wiring
Last-modified: Wed Dec  9 03:16:27 EST 1992

        Frequently Asked Questions on Electrical Wiring

        Steven Bellovin ([e-mail])
        Chris Lewis ([e-mail])

        Comments to (automatic if you reply to this article):
            [e-mail]

This FAQ is formatted as a digest.  Most news readers can
skip from one question to the next by pressing ^G.

Answers to many other topics related to houses can be obtained from
the misc.consumers.house archive; send an empty piece of mail to
[e-mail] for information.

Changes to previous issue marked with "|" in left column.  Watch
particularly for "NEW" in the Questions list for new or substantively
changed answers.

Note that this is now a registered FAQ - cross-posted to news.answers
and should appear in the FAQ list of lists.

Subject: Questions answered in this FAQ

    Introduction/Disclaimers
    What is the NEC?  Where can I get a copy?
    What is the CEC?  Where can I get a copy?
|    Can I do my own wiring?  Extra pointers?
    What do I need in the way of tools?
    What is UL listing?
    What is CSA approval?
    Are there any cheaper, easier to read books on wiring?
    Inspections how and what?  Why should I get my wiring inspected?
    My house doesn't meet some of these rules and regulations.
|    A word on voltages: 110/115/117/120/125/220/240 (NEW)
    What does an electrical service look like?
    What is a circuit?
    "grounding" versus "grounded" versus "neutral".
    What does a fuse or breaker do?  What are the differences?
    Breakers?  Can't I use fuses?
    What size wire should I use?
    Where do these numbers come from?
    What does "14-2" mean?
    What is a "wirenut"/"marrette"/"marr connector".  How are they used?
    What is a GFI/GFCI?
    Where should GFCIs be used?
    Where shouldn't I use a GFCI?
    What is the difference between a GFCI outlet and a GFCI breaker?
    What's the purpose of the ground prong on an outlet, then?
    Why is one prong wider than the other?  Polarization
    What kind of outlets do I need in a kitchen?
    Where must outlets and switches be in bathrooms?
    What is Romex/NM/NMD?  What is BX?  When should I use each?
    Should I use plastic or metal boxes?
    Junction box positioning?
    Can I install a replacement fixture?
    What does it mean when the lights brighten when a motor starts?
    What is 3 phase power?  Should I use it?  Can I get it in my house?
    Is it better to run motors at 110 or 220?
    What is this nonsense about 3HP on 110V 15A circuits?
    How do I convert two prong receptacles to three prong?
    Are you sure about GFCIs and ungrounded outlets?
        Should the test button work?
    How should I wire my shop?
    Underground wiring
    Aluminum wiring
    I'm buying a house!  What should I do?
    What is this weird stuff?  Old style wiring
    Where do I buy stuff?


Subject: Introduction/Disclaimers

    Although we've done a fair bit of wiring, we are not
    electricians, and we cannot be responsible for what you do.  If
    you're at all uncertain about what is correct or safe, *don't
    do it*.  Contact someone qualified -- a licensed electrician,
    or your local electrical inspector.  Electricity is no joke;
    mistakes can result in shocks, fires, or electrocution.

    Furthermore, our discussion is based on the U.S. National
    Electrical Code (NEC) and the Canadian Electrical code (CEC).
    To the best of our abilities, we have confirmed every detail
    with the electrical code, but we don't quote sections
    simply to keep this thing readable.  If you think we're wrong,
    we invite you to correct us, but please - quote references!

    The NEC and the CEC do not, in and of themselves, have the
    force of law.  Many municipalities adopt it en toto.  Others,
    however, do not.  Check your with your local building
    department (and <provincial> Hydro Inspection Offices in
    Canada) to find out what applies in your area.  Also,
    your local electrical utility may also have special requirements
    for electrical service installation.  Bear in mind, too, that
    we say here applies primarily to ordinary single-family
    residences.  Multi-family dwellings, mobile homes, commercial
    establishments, etc., are sometimes governed by different
    rules.

    Also note that, contrary to popular belief in the U.S. (and in
    some parts of Canada), Canada is not a wholly-owned subsidiary
    of the U.S.  Consequently, the NEC does not apply in Canada.
    Lots of things are the same, including voltages, line
    frequencies, and the laws of physics.  But there are a number
    of crucial differences in the regulations.  Where we can, we've
    noted them, flagging the relevant passages with ``NEC'' or
    ``CEC''.

    Remember that the CEC and NEC are minimal standards.  It is often
    smart to go beyond their minimal requirements.

Subject: What is the NEC?  Where can I get a copy?

    The NEC is a model electrical code devised and published by the
    National Fire Protection Association, an insurance industry group.
    It's revised every three years.  The 1993 version will be
    released in September, 1992.  You can buy a copy at a decent
    bookstore, or by calling them directly at 800-344-3555.  The
    code exists in several versions.  There's the full text, which
    is fairly incomprehensible.  There's an abridged edition, which
    has only the sections likely to apply to most houses.  And
    there's the NEC Handbook, which contains the ``authorized
    commentary'' on the code, as well as the full text.  That's the
    recommended version.  Unfortunately, there's no handbook for
    the abridged edition.  And the full handbook is expensive --
    US$65 plus shipping and handling.

Subject: What is the CEC?  Where can I get a copy?

    The Canadian Standards Association is an organization made up
    of various government agencies, power utilities, insurance
    companies, electrical manufacturers and other organizations.
    The CSA publishes CSA Standard C22.1 which is updated every two
    or three years.  Each province adopts, with some amendments,
    this standard and publishes a province-specific code book.
    Since each province publishes its own slightly modified
    standard, it would be somewhat confusing to obtain the CSA
    standard itself.  In this FAQ, "CEC" really means the
    appropriate provincial standard.  In particular, this FAQ is
    derived from the Ontario Hydro Electrical Safety Code, 20th
    edition (1990).  Which is in turn based on CSA C22.1-1990 (16th
    edition).  While differences exist between the provinces, an
    attempt has been made to avoid specific-to-Ontario detail.

    The appropriate provincial code can be obtained from electrical
    inspection offices of your provincial power authority.  In
    Ontario, it's Ontario Hydro.  The Ontario Hydro book isn't
    overly fat.  It's about C$25, and includes mailed updates.  I
    hear that these standards are somewhat easier to read than the
    equivalent NEC publications.

    Don't bother asking in Quebec - DIY wiring is banned throughout
    the province.

Subject: Can I do my own wiring?  Extra pointers?

    In most places, homeowners are allowed to do their own wiring.
    In some, they're not.  Check with your local electrical
    inspector.  Most places won't permit you to do wiring on other's
    homes for money without a license.  Nor are you permitted to do
    wiring in "commercial" buildings.  Multiple dwellings (eg: duplexes)
    are usually considered "semi-commercial" or "commercial".  However,
    many jurisdictions will permit you to work on semi-commercial
    wiring if you're supervised by a licensed electrician - if you can
    find one willing to supervise.

    If you do your own wiring, an important point:

    Do it NEAT and WELL!  What you really want to aim for is a better
    job than an electrician will do.  After all, it's your own home,
    and it's you or your family that might get killed if you make
    a mistake.  An electrician has time pressures, has the skills
    and knows the tricks of the trade to do a fast, safe job.
    In this FAQ we've consciously given a few recommendations that
    are in excess of code, because we feel that it's reasonable,
    and will impress the inspector.

    The inspector will know that you're an amateur.  You have to
    earn his trust.  The best way of doing this is to spend your
    time doing as neat a job as possible.  Don't cut corners.
    Exceed specifications.  Otherwise, the inspector may get extremely
    picky and fault you on the slightest transgressions.

    Don't try to hide anything from the inspector.

    Use the proper tools.  Ie: don't use a bread knife to strip
    wires, or twist wires with your fingers.  The inspector
    won't like it, and the results won't be that safe.  And it
    takes longer.  And you're more likely to stick a hunk of
    12ga wire through your hand that way.

    Don't handle house wire when it's very cold (eg: below -10C
    or 16F).  Thermoplastic house wire, particularly older types
    become very brittle.

Subject: What do I need in the way of tools?

    First, there's the obvious -- a hammer, a drill, a few
    screwdrivers, both straight and Phillips-head.  If you're
    lucky enough to live in Canada (or find a source of CSA-approved
    devices) you need Robertson ("square recess") screwdrivers
    (#1 and #2) instead of phillips.

    For drilling a few holes, a 3/4" or 1" spade bit and 1/4" or
    3/8" electric drill will do.  If you're doing a lot, or
    are working with elderly lumber, we recommend a 1/2" drill
    (right-angle drills are wonderful.  Can be rented) and
    3/4" or 1" screw-point auger drill bits.  These bits pull
    you through, so they're much faster and less fatiguing, even
    in 90 year old hardwood timbers.

    Screw-driver bits are useful for drills, expecially if you
    install your electrical boxes using screws (drywall screws
    work well).

    For stripping wire, use a real wire stripper, not a knife or
    ordinary wire cutters.  Don't buy the $3 K-mart "combo stripper,
    crimper and bottle opener" types.  You should expect to pay
    $15 to $20 for a good "plier-type" pair.  It will have sized
    stripping holes, and won't nick or grab the wire - it should
    be easy to strip wire with it.  One model has a small hole in the
    blade for forming exact wire loops for screw terminals.  There
    are fancier types (autostrip/cut), but they generally aren't
    necessary, and pros usually don't use them.

    A pair of diagonal side cutter pliers are useful for clipping ends
    in constricted places.  Don't use these for stripping wire.

    You will need linesman pliers for twisting wires for wire nuts.

    You should have a pair of needle-nose pliers for fiddling
    inside boxes and closing loops, but it's better to form wire
    loops with a "loop former hole" on your wire stripper - more
    accurate.

    If you're using non-metallic cable, get a cable stripper for
    removing the sheath.  Or, do what some pros do, they nick the
    end of the sheath, grab the ground wire with a pair of pliers,
    and simply rip the sheath back using the ground wire as a
    "zipper", and cut the sheath off.  You shouldn't try to strip
    the sheath with a knife point, because it's too easy to
    slash the insulation on the conductors.

    For any substantial amount of work with armored cable, it's well
    worth your while to invest in a rotary cable splitter (~US$ 18).
    Hack saws are tricky to use without cutting into the wire
    or the insulation.

    Three-prong outlet testers are a quick check for properly-wired
    outlets.  About $6.  Multimeters tell you more, but are a lot more
    expensive, and probably not worth it for most people.  A simple
    voltage sensor, which can detect potential through an insulated
    wire not supplying any devices, is extremely helpful; they cost
    about US$ 10 at Radio Shack.

    You should have a voltage detector - to check that the wires are
    dead before doing work on them.  Neon-bulb version are cheap ($2-3)
    and work well.  If you get more serious, a "audible alarm" type is
    good for tracing circuits without a helper.  (Though I've been known
    to lock the drill on, and hit breakers until the scream stops ;-)

    For running wires through existing walls, you need fish tape.
    Often, two tapes are needed, though sometimes, a bent hanger or
    a length of thin chain will suffice.  Fish tapes can be rented.

    Electrical tape.  Lots of it ;-)  Seriously, a good and competent
    wiring job will need very little tape.  The tape is useful for
    wrapping dicy insulation in repair work.  Another use is to wrap
    around the body of outlets and switches to cover the termination
    screws - I don't do this, but drywall contractors prefer it (to
    prevent explosions when the drywall knife collides with a live outlet
    that has no cover plate).

Subject: What is UL listing?

    The UL stands for "Underwriters Laboratory", which is a
    insurance industry organization that tests electrical
    components and equipment for potential hazards.  When something
    is UL-listed, that means that the UL has tested the device,
    and it meets their requirements for safety - ie: fire or shock
    hazard.  It doesn't necessarily mean that the device actually does
    what it's supposed to, just that it probably won't kill you.

    The UL does not have power of law in the U.S. -- you are
    permitted to buy and install non-UL-approved devices.  However,
    insurance policies sometimes have clauses in them that will
    limit their liability in case of a claim made in response to
    the failure of a non-UL-approved device.  Furthermore, in
    many situations the NEC will require a device ``listed'' for
    some purpose.  What they mean is a device that UL has approved.
    There is thus the indirect force of law.

Subject: What is CSA approval?

    Every electrical device or component must be certified by the
    Canadian Standards Association before it can be sold in
    Canada.  Implicit in this is that all wiring must be done
    with CSA-approved materials.  They perform testing similar to
    the UL (a bit more stringent), except that CSA approval is
    required by law.

    Again, like the UL, if a fire was caused by non-CSA-approved
    equipment, your insurance company may not have to pay the
    claim.

    In Canada, there is a branch organization of the UL, called ULC
    (UL of Canada).  ULC does not have power of law, and seems to
    be more a liason group between the CSA and insurance
    companies.

Subject: Are there any cheaper, easier to read books on wiring?

    USA: The following three books were suggested by our readers

        Residential Wiring
        by Jeff Markell,
        Craftsman Books,
        Carlsbad CA for $18.25. ISBN 0-934041-19-9.

        Practical Electrical Wiring
        Residential, Farm and Industrial,  Based on the National
        Electrical Code    ANSI/NFPA 70
        Herbert P. Richter and W. Creighton Schwan
        McGraw-Hill Book Co.

        Wiring Simplified
        H. P. Richter and W. C. Schwan
        Park Publishing Co.

    Try to make sure that the book is based on the latest NEC
    revision.  Which is currently 1990.

    Canada: P.S. Knight authors and publishes a book called
    "Electrical Code Simplified".  There appears to be a version
    published specific to each province, and is very tied into the
    appropriate provincial code.  It focuses on residential wiring,
    and is indispensible for Canadian DIY'ers.  It is better to get
    this book than the CEC unless you do a lot of wiring (or answer
    questions on the net ;-).

    It is updated each time the provincial codes are.  This book is
    available at all DIY and hardware stores for less than C$10.

Subject: Inspections how and what?  Why should I get my wiring inspected?

    Most jurisdictions require that you obtain a permit and
    inspections of any wiring that is done.  Amongst other more
    mundane bureaucratic reasons (like insurance companies not
    liking to have to pay claims), a permit and inspections
    provides some assurance that you, your family, your neighbors
    or subsequent owners of your home don't get killed or lose
    their homes one night due to a sloppy wiring job.

    Most jurisdictions have the power to order you to vacate your
    home, or order you to tear out any wiring done without a
    permit.  California, for instance, is particularly nasty about
    this.

    If fire starts in your home, and un-inspected wiring is at
    fault, insurance companies will often refuse to pay the damage
    claims.

    In general, the process goes like this:
        - you apply to your local inspections office or building
          department for a permit.  You should have a sketch or
          detailed drawing of what you plan on doing.  This is
          a good time to ask questions on any things you're not
          sure of.  If you're doing major work, they may impose
          special conditions on you, require loading
          calculations and ask other questions.  At this point
          they will tell you which inspections you will need.
        - If you're installing a main panel, you will need to
          have the panel and service connections inspected
          before your power utility will provide a connection.
          This is sometimes done by the local power authority
          rather than the usual inspectors.
        - After installing the boxes and wiring, but before
          the insulation/walls go up, you will need a
          "rough-in" inspection.
        - After the walls are up, and the wiring is complete,
          you will need a "final inspection".

Subject: My house doesn't meet some of these rules and regulations.
    Do I have to upgrade?

    In general, there is no requirement to upgrade older dwellings,
    though there are some exceptions (ie: smoke detectors in some
    cases).  However, any new work must be done according to the
    latest electrical code.  Also, if you do ``major'' work, you
    may be required to upgrade certain existing portions or all
    of your system.  Check with your local electrical inspector.

Subject: A word on voltages: 110/115/117/120/125/220/240 (NEW)

    One thing where things might get a bit confusing is the
    different numbers people bandy about for the voltage of
    a circuit.  One person might talk about 110V, another 117V
    or another 120V.  These are all, in fact, exactly the same
    thing...  In North America the utility companies are required
    to supply a split-phase 240 volt (+-5%) feed to your house.
    This works out as two 120V legs.  However since there are
    resistive voltage drops in the house wiring, it's not
    unreasonable to find 120V has dropped to 110V or 240V has dropped
    to 220V by the time the power reaches a wall outlet.  Especially
    at the end of an extension cord or long circuit run.  For a number
    of reasons, some historical, some simple personal orneryness,
    different people choose call them by slightly different numbers.
    This FAQ has chosen to be consistent with calling them "110V" and
    "220V", except when actually saying what the measured voltage will
    be.  Confusing?  A bit.  Just ignore it.

|    208V is *not* the same as 240V.  208V is the voltage between
|    phases of a 3-phase "Y" circuit that is 120V from neutral to any
|    hot.  277V is the voltage between hot and neutral of a 3-phase
|    "Y" circuit that's 480V between phases.

Subject: What does an electrical service look like?

    There are logically four wires involved with supplying the
    main panel with power.  Three of them will come from the utility
    pole, and a fourth (bare) wire comes from elsewhere.

     The bare wire is connected to one or more long metal bars pounded
     into the ground, or to a wire buried in the foundation, or sometimes
     to the water supply pipe (has to be metal, continuous to where
    the main water pipe entering the house.  Watch out for galvanic
    action conductivity "breaks" (often between copper and iron pipe)).
    This is the "grounding conductor".  It is there to make sure that
    the third prong on your outlets is connected to ground.  This wire
    normally carries no current.

    One of the other wires will be white (or black with white or
    yellow stripes, or sometimes simply black).  It is the neutral wire.
    It is connected to the "centre tap" (CEC; "center tap" in the
    NEC) of the distribution transformer supplying the power.  It
    is connected to the grounding conductor in only one place (often
    inside the panel).  The neutral and ground should not be connected
    anywhere else.  Otherwise, weird and/or dangerous things may happen.

    Furthermore, there should only be one grounding system in
    a home.  Some codes require more than one grounding electrode.
    These will be connected together, or connected to the neutral
    at a common point - still one grounding system.  Adding additional
    grounding electrodes connected to other portions of the house
    wiring is unsafe and contrary to code.

    If you add a subpanel, the ground and neutral are usually
    brought as separate conductors from the main panel, and are
    not connected together in the subpanel (ie: still only one
    neutral-ground connection).  However, in some situations
    (certain categories of separate buildings) you actually do
    have to provide a second grounding electrode - consult your
    inspector.

    The other two wires will usually be black, and are the "hot"
    wires.  They are attached to the distribution transformer as
    well.

    The two black wires are 180 degrees out of phase with each
    other.  This means if you connect something to both hot wires,
    the voltage will be 220 volts.  If you connect something to the
    white and either of the two blacks you will get 110V.

    Some panels seem to only have three wires coming into them.
    This is either because the neutral and ground are connected
    together at a different point (eg: the meter or pole) and one
    wire is doing dual-duty as both neutral and ground, or in some
    rare occasions, the service has only one hot wire (110V only
    service).

Subject: What is a circuit?

    Inside the panel, connections are made to the incoming wires.
    These connections are then used to supply power to selected
    portions of the home.  There are three different combinations:
        1) one hot, one neutral, and ground: 110V circuit.
        2) two hots, no neutral, and ground: 220V circuit.
        3) two hots, neutral, and ground: 220V circuit + neutral,
           and/or two 110V circuits with a common neutral.

    (1) is used for most circuits supplying receptacles and
    lighting within your house.  (3) is usually used for supplying
    power to major appliances such as stoves, and dryers - they
    often have need for both 220V and 110V, or for bringing several
    circuits from the panel box to a distribution point.  (2) is
    usually for special 220V motor circuits, electric heaters, or
    air conditioners.

    [Note: In the US, the NEC frequently permits a circuit similar
    to (2) be used for stoves and dryers - namely, that there
    are two hot wires, and a wire that does dual duty as neutral
    and ground, and is connected to the frame as well as providing
    the neutral for 110V purposes - three prong plugs instead
    of four (*only* for stoves/dryers connected to the main panel.
    When connected to most sub-panels, 4 prong plugs and receptacles
    are required).  In our not-so-humble opinion this is crazy, but
    the NFPA claims that this practice was re-evaluated for the 1992 NEC,
    and found to be safe.  Check your local codes, or inquire as to
    local practice -- there are restrictions on when this is
    permissible.]

    (1) is usually wired with three conductor wire: black for hot,
    white for neutral, and bare for grounding.

    (2) and (3) have one hot wire coloured red, the other black, a
    bare wire for grounding, and in (3) a white wire for neutral.

    You will sometimes see (2) wired with just a black, white and ground
    wire.  Since the white is "hot" in this case, both the NEC and CEC
    requires that the white wire be "permanently marked" at the ends
    to indicate that it is a live wire.  Usually done with paint, nail
    polish or sometimes electrical tape.

    Each circuit is attached to the main wires coming into the
    panel through a circuit breaker or fuse.

    There are, in a few locales, circuits that look like (1), (2)
    or (3) except that they have two bare ground wires.  Some places
    require this for hot tubs and the like (one ground is "frame ground",
    the other attaches to the motor).  This may or may not be an
    alternative to GFCI protection.

Subject: "grounding" versus "grounded" versus "neutral".

    According to the terminology in the CEC and NEC, the
    "grounding" conductor is for the safety ground, i.e., the green
    or bare wire.  The word "neutral" is reserved for the white when
    you have a circuit with more than one "hot" wire.  Since the white
    wire is connected to neutral and the grounding conductor inside the
    panel, the proper term is "grounded conductor".  However, the
    potential confusion between "grounded conductor" and "grounding
    conductor" can lead to potentially lethal mistakes - you should
    never use the bare wire as a "grounded conductor" or white wire
    as the "grounding conductor", even though they are connected
    together in the panel.

    [But not in subpanels - subpanels are fed neutral and ground
    separately from the main panel.  Usually.]

    In the trade, and in common usage, the word "neutral" is used
    for "grounded conductor".  This FAQ uses "neutral" simply to
    avoid potential confusion.  We recommend that you use "neutral"
    too.  Thus the white wire is always (except in some light
    switch applications) neutral.  Not ground.

Subject: What does a fuse or breaker do?  What are the differences?

    Fuses and circuit breakers are designed to interrupt the power
    to a circuit when the current flow exceeds safe levels.  For
    example, if your toaster shorts out, a fuse or breaker should
    "trip", protecting the wiring in the walls from melting.  As
    such, fuses and breakers are primarily intended to protect the
    wiring -- UL or CSA approval supposedly indicates that the
    equipment itself won't cause a fire.

    Fuses contain a narrow strip of metal which is designed to melt
    (safely) when the current exceeds the rated value, thereby
    interrupting the power to the circuit.  Fuses trip relatively
    fast.  Which can sometimes be a problem with motors which have
    large startup current surges.  For motor circuits, you can use
    a "time-delay" fuse (one brand is "fusetron") which will avoid
    tripping on momentary overloads.  A fusetron looks like a
    spring-loaded fuse.  A fuse can only trip once, then it must be
    replaced.

    Breakers are fairly complicated mechanical devices.  They
    usually consist of one spring loaded contact which is latched
    into position against another contact.  When the current flow
    through the device exceeds the rated value, a bimetallic strip
    heats up and bends.  By bending it "trips" the latch, and the
    spring pulls the contacts apart.  Circuit breakers behave
    similarly to fusetrons - that is, they tend to take longer to
    trip at moderate overloads than ordinary fuses.  With high
    overloads, they trip quickly.  Breakers can be reset a finite
    number of times - each time they trip, or are thrown
    when the circuit is in use, some arcing takes place, which
    damages the contacts.  Thus, breakers should not be used in
    place of switches unless they are specially listed for the
    purpose.

    Neither fuses nor breakers "limit" the current per se.  A dead
    short on a circuit can cause hundreds or sometimes even
    thousands of amperes to flow for a short period of time, which
    can often cause severe damage.

Subject: Breakers?  Can't I use fuses?

    Statistics show that fuse panels have a significantly higher
    risk of causing a fire than breaker panels.  This is usually
    due to the fuse being loosely screwed in, or the contacts
    corroding and heating up over time, or the wrong size fuse
    being installed, or the proverbial "replace the fuse with a
    penny" trick.

    Since breakers are more permanently installed, and have better
    connection mechanisms, the risk of fire is considerably less.

    Fuses are prone to explode under extremely high overload.  When
    a fuse explodes, the metallic vapor cloud becomes a conducting
    path.  Result? from complete meltdown of the electrical panel,
    melted service wiring, through fires in the electrical
    distribution transformer and having your house burn down.
    Breakers don't do this.

    Many jurisdictions, particularly in Canada, no longer permit
    fuse panels in new installations.  The NEC does permit new
    fuse panels in some rare circumstances (requiring the special
    inserts to "key" the fuseholder to specific size fuses)

    Some devices, notably certain large air conditioners, require fuse
    protection in addition to the breaker at the panel.  The fuse
    is there to protect the motor windings from overload.  Check the
    labeling on the unit.  This is usually only on large permanently
    installed motors.  The installation instructions will tell you
    if you need one.

Subject: What size wire should I use?

    For a 20 amp circuit, use 12 gauge wire.  For a 15 amp circuit,
    you can use 14 gauge wire (in most locales).  For a long run,
    though, you should use the next larger size wire, to avoid
    voltage drops.  12 gauge is only slightly more expensive than
    14 gauge, though it's stiffer and harder to work with.

    Here's a quick table for normal situations.  Go up a size for
    more than 100 foot runs, when the cable is in conduit, or
    ganged with other wires in a place where they can't dissipate
    heat easily:

        Gauge        Amps
        14        15
        12        20
        10        30
        8        40
        6        65

    We don't list bigger sizes because it starts getting very dependent
    on the application and precise wire type.

Subject: Where do these numbers come from?

    There are two considerations, voltage drop and heat buildup.
    The smaller the wire is, the higher the resistance is.  When
    the resistance is higher, the wire heats up more, and there is
    more voltage drop in the wiring.  The former is why you need
    higher-temperature insulation and/or bigger wires for use in
    conduit; the latter is why you should use larger wire for long
    runs.

    Neither effect is very significant over very short distances.
    There are some very specific exceptions, where use of smaller
    wire is allowed.  The obvious one is the line cord on most
    lamps.  Don't try this unless you're certain that your use fits
    one of those exceptions; you can never go wrong by using larger
    wire.

Subject: What does "14-2" mean?

    This is used to describe the size and quantity of conductors
    in a cable.  The first number specifies the gauge.  The second
    the number of current carrying conductors in the wire - but
    remember there's usually an extra ground wire.  "14-2" means
    14 gauge, two insulated current carrying wires, plus bare ground.

    -2 wire usually has a black, white and bare ground wire.  Sometimes
    the white is red instead for 220V circuits without neutral.  In
    the latter case, the sheath is usually red too.

    -3 wire usually has a black, red, white and bare ground wire.
    Usually carrying 220V with neutral.

Subject: What is a "wirenut"/"marrette"/"marr connector"?  How are they
    used?

    A wire nut is a cone shaped threaded plastic thingummy that's used
    to connect wires together.  "Marrette" or "Marr connector"
    are trade names.  You'll usually use a lot of them in DIY wiring.

    In essence, you strip the end of the wires about an inch, twist them
    together, then twist the wirenut on.

    Though some wirenuts advertise that you don't need to twist the
    wire, do it anyways - it's more mechanically and electrically
    secure.

    There are many different sizes of wire nut.  You should check
    that the wire nut you're using is the correct size for the
    quantity and sizes of wire you're connecting together.

    Don't just gimble the wires together with a pair of pliers or
    your fingers.  Use a pair of blunt nose ("linesman") pliers,
    and carefully twist the wires tightly and neatly.  Sometimes
    it's a good idea to trim the resulting end to make sure it
    goes in the wirenut properly.

    Some people wrap the "open" end of the wirenut with electrical
    tape.  This is probably not a good idea - the inspector may
    tear it off during an inspection.  It's usually done because
    a bit of bare wire is exposed outside the wire nut - instead
    of taping it, the connection should be redone.

Subject: What is a GFI/GFCI?

    A GFCI is a ``ground-fault circuit interrupter''.  It measures
    the current current flowing through the hot wire and the
    neutral wire.  If they differ by more than a few milliamps, the
    presumption is that current is leaking to ground via some other
    path.  This may be because of a short circuit to the chassis of
    an appliance, or to the ground lead, or through a person.  Any
    of these situations is hazardous, so the GFCI trips, breaking
    the circuit.

    GFCIs do not protect against all kinds of electric shocks.  If,
    for example, you simultaneously touched the hot and neutral
    leads of a circuit, and no part of you was grounded, a GFCI
    wouldn't help.  All of the current that passed from the hot
    lead into you would return via the neutral lead, keeping the
    GFCI happy.

    The two pairs of connections on a GFCI outlet are not symmetric.
    One is labeled LOAD; the other, LINE.  The incoming power feed
    *must* be connected to the LINE side, or the outlet will not be
    protected.  The LOAD side can be used to protect all devices
    downstream from it.  Thus, a whole string of outlets can be
    covered by a single GFCI outlet.

Subject: Where should GFCIs be used?

    The NEC mandates GFCIs for 110V, 15A or 20A single phase
    outlets, in bathrooms, kitchens within 6' of the sink, garages,
    unfinished basements or crawl spaces, outdoors, near a pool, or
    just about anywhere else where you're likely to encounter water
    or dampness.  There are exceptions for inaccessible outlets,
    those dedicated to appliances ``occupying fixed space'',
    typically refrigerators and freezers, and for sump pumps and
    laundry appliances.

    The CEC does not mandate as many GFCIs.  In particular, there
    is no requirement to protect kitchen outlets, or most garage or
    basement outlets.  Basement outlets must be protected if you
    have a dirt floor, garage outlets if they're near the door to
    outside.  Bathrooms and most exterior outlets must have GFCIs.

    Even if you are not required to have GFCI protection, you may
    want to consider installing it anyway.  Unless you need a GFCI
    breaker (see below), the cost is low.  In the U.S., GFCI
    outlets can cost as little as US$8.  (Costs are a bit higher in
    Canada:  C$12.)  Evaluate your own risk factors.  Does your
    finished basement ever get wet?  Do you have small children?
    Do you use your garage outlets to power outdoor tools?  Does
    water or melted snow ever puddle inside your garage?

Subject: Where shouldn't I use a GFCI?

    GFCIs are generally not used on circuits that (a) don't pose a
    safety risk, and (b) are used to power equipment that must run
    unattended for long periods of time.  Refrigerators, freezers,
    and sump pumps are good examples.  The rationale is that GFCIs
    are sometimes prone to nuisance trips.  Some people claim that
    the inductive delay in motor windings can cause a momentary
    current imbalance, tripping the GFCI.  Note, though, that most
    GFCI trips are real; if you're getting a lot of trips for no
    apparent reason, you'd be well-advised to check your wiring
    before deciding that the GFCI is broken or useless.

Subject: What is the difference between a GFCI outlet and a GFCI breaker?

    For most situations, you can use either a GFCI outlet as the
    first device on the circuit, or you can install a breaker with
    a built-in GFCI.  The former is generally preferred, since GFCI
    breakers are quite expensive.  For example, an ordinary GE
    breaker costs ~US$5; the GFCI model costs ~US$35.  There is one
    major exception:  if you need to protect a ``multi-wire branch
    circuit'' (two or more circuits sharing a common neutral wire),
    such as a Canadian-style kitchen circuit, you'll need a
    multi-pole GFCI breaker.  Unfortunately, these are expensive;
    the cost can range into the hundreds of dollars, depending on
    what brand of panel box you have.  But if you must protect such
    a circuit (say, for a pool heater), you have no choice.

    One more caveat -- GFCI outlets are bulky.  You may want to use
    an oversize box when installing them.  On second thought, use
    large (actually deep) boxes everywhere.  You'll thank yourself for it.

    Incidentally, if you're installing a GFCI to ensure that one
    specific outlet is protected (such as a bathroom), you don't
    really have to go to all of the trouble to find the first
    outlet in the circuit, you could simply find the first outlet
    in the bathroom, and not GFCI anything upstream of it.  But
    protecting the whole circuit is preferred.

    When you install a GFCI, it's a good idea to use the little
    "ground fault protected" stickers that come with it and mark
    the outlets downstream of the GFCI.  You can figure out which
    outlets are "downstream", simply by tripping the GFCI with the
    test button and see which outlets are dead.

Subject: What's the purpose of the ground prong on an outlet, then?

    Apart from their use in electronics, which we won't comment on,
    and for certain fluorescent lights (they won't turn on without
    a good ground connection), they're intended to guard against
    insulation failures within the device.  Generally, the case of
    the appliance is connected to the ground lead.  If there's an
    insulation failure that shorts the hot lead to the case, the
    ground lead conducts the electricity away safely (and possibly
    trips the circuit breaker in the process).  If the case is not
    grounded and such a short occurs, the case is live -- and if
    you touch it while you're grounded, you'll get zapped.  Of
    course, if the circuit is GFCI-protected, it will be a very
    tiny zap -- which is why you can use GFCIs to replace
    ungrounded outlets (both NEC and CEC).

    There are some appliances that should *never* be grounded.  In
    particular, that applies to toasters and anything else with
    exposed conductors.  Consider:  if you touch the heating
    electrode in a toaster, and you're not grounded, nothing will
    happen.  If you're slightly grounded, you'll get a small shock;
    the resistance will be too high.  But if the case were
    grounded, and you were holding it, you'd be the perfect path to
    ground...

Subject: Why is one prong wider than the other?  Polarization

    Nowadays, many two-prong devices have one prong wider than the
    other.  This is so that the device could rely (not guaranteed!)
    on one specific wire being neutral, and the other hot.
    This is particularly advantageous in light fixtures, where the
    the shell should neutral (safety), or other devices which want to
    have an approximate ground reference (ie: some radios).

    Most 2-prong extension cords have wide prongs too.

    This requires that you wire your outlets and plugs the right
    way around.  You want the wide prong to be neutral, and the
    narrow one hot.  Most outlets have a darker metal for the
    hot screw, and lighter coloured screw for the neutral.
    If not, you can usually figure out which is which by which
    prong the terminating screw connects to.

Subject: What kind of outlets do I need in a kitchen?

    The NEC requires at least two 20 amp ``small appliance
    circuits'' for kitchens.  The CEC requires split-duplex
    receptacles.  Outlets must be installed such that no point is more
    than 24" (NEC) (900 mm CEC) from an outlet.  Every counter wider
    than 12" (NEC) or 300 mm (CEC) must have at least one outlet.
    The circuit these outlets are on may not feed any outlets except
    in the kitchen, pantry, or dining room.  Furthermore, these circuits
    are in addition to any required for refrigerators, stoves, microwaves,
    lighting, etc.  Non-dedicated outlets within 6' of a sink *must* be
    protected by a GFCI (NEC only).

    Split duplex receptacles are fed with a 220V circuit.  The tab
    is broken on the hot side of the outlet, and one hot goes to
    the upper outlet, and the other hot goes to the lower outlet.
    The neutral connects to both outlets through one screw.  When
    "carrying through" to another outlet, the neutral must be
    pigtailed, such that removing the outlet, or having the neutral
    connection fall off doesn't cause the neutral to disconnect
    from downstream outlets.

Subject: Where must outlets and switches be in bathrooms?

    There must be at least one outlet in each bathroom, adjacent to
    the sink, in addition to any outlet that may be incorporated in
    the light fixture.  All such outlets *must* be GFCI-protected.

Subject: What is Romex/NM/NMD?  What is BX?  When should I use each?

    Romex is a brand name for a type of plastic insulated wire.
    Sometimes called non-metallic sheath.  The formal name is NM.
    This is suitable for use in dry, protected areas (ie: inside
    stud walls, on the sides of joists etc.), that are not subject
    to mechanical damage or excessive heat.  Most newer homes are
    wired almost exclusively with NM wire.  There are several
    different categories of NM cable.

    BX cable -- technically known as armored cable or "AC" has a
    flexible aluminum or steel sheath over the conductors and is
    fairly resistant to damage.

    TECK cable is AC with an additional external thermoplastic
    sheath.

    Protection for cable in concealed locations: where NM or AC cable
    is run through studs, joists or similar wooden members, the outer
    surface of the cable must be kept at least 32mm/1.25" (CEC & NEC)
    from the edges of the wooden members, or the cable should be protected
    from mechanical injury.  This latter protection can take the form of
    metal plates (such as spare outlet box ends) or conduit.

    [Note: inspector-permitted practise in Canada suggests that armored
    cable, or flexible conduit can be used as the mechanical protection,
    but this is technically illegal.]

    Additional protection recommendations (these are rules in the
    Canadian codes - they are reasonable answers to the vague
    references to "exposed to mechanical damage" in both the NEC
    and CEC):

        - NM cable should be protected against mechanical damage
          where it passes through floors or on the surface of walls
          in exposed locations under 5 feet from the floor.
          Ie: use AC instead, flexible conduit, wooden guards etc.
        - Where cable is suspended, as in, connections to furnaces
          or water heaters, the wire should be protected.  Canadian
          practise is usually to install a junction or outlet
          box on the wall, and use a short length of AC cable
          or NM cable in flexible conduit to "jump" to the appliance.
          Stapling NM to a piece of lumber is also sometimes used.
        - Where NM cable is run in close proximity to heating
          ducts or pipe, heat transfer should be minimized by
          means of a 25mm/1" air space, or suitable insulation
          material (a wad of fiberglass).
        - NM cable shall be supported within 300mm/1' of every box
          or fitting, and at intervals of no more than 1.5m/5'.
          Holes in joists or studs are considered "supports".
          Some slack in the cable should be provided adjacent to
          each box.  [while fishing cable is technically in violation,
          it is permitted where "proper" support is impractical]
        - 2 conductor NM cable should never be stapled on edge.
          [Knight also insists on only one cable per staple, referring
          to the "workmanship" clause, but this seems more honoured
          in the breach...]
        - cable should never be buried in plaster, cement or
          similar finish.
        - cable should be protected where it runs behind baseboards.
        - Cable may not be run on the upper edge of ceiling joists
          or the lower edges of rafters where the headroom is more
          than 1m (39").

    Whenever BX cable is terminated at a box with a clamp, small
    plastic bushings must be inserted in the end of the cable to
    prevent the clamps forcing the sharp ends of the armor through
    the insulation.

    BX is sometimes a good idea in a work shop unless covered by
    solid wall coverings.

    In places where damage is more likely (like on the back wall of
    a garage ;-), you may be required to use conduit, a
    UL- (or CSA-) approved metal pipe.  You use various types of
    fittings to join the pipe or provide entrance/exit for the
    wire.

    Service entrances frequently use a plastic conduit.

    In damp places (eg: buried wiring to outdoor lighting) you will
    need special wire (eg: CEC NMW90, NEC UF).  NMW90 looks like
    very heavy-duty NMD90.  You will usually need short lengths of
    conduit where the wire enters/exits the ground.  [See underground
    wiring section.]

     Thermoplastic sheath wire (such as NM, NMW etc.) should not be
     exposed to direct sunlight unless explicitly approved for that
     purpose.

     Canada appears to use similar wire designations to the US,
     except that Canadian wire designations usually include the
     temperature rating in Celsius.  Eg: "AC90" versus "AC".
    In the US, NM-B is 90 degrees celcius.

    NOTE: local codes vary.  This is one of the items that changes
    most often.  Eg: Chicago codes require conduit *everywhere*.
    There are very different requirements for mobile homes.
    Check your local codes, *especially* if you're doing anything
    that's the slightest out of the ordinary.

    Wire selection table (incomplete - the real tables are enormous,
    uncommon wire types or applications omitted)

    Condition            Type    CEC    NEC

    Exposed/Concealed dry        plastic    NMD90    NM
                    armor    AC90    AC
                        TECK90

    Exposed/Concealed damp        plastic    NMD90    NMC
                    armor    ACWU90
                        TECK90

    Exposed/Concealed wet        plastic    NMWU90
                    armor    ACWU90
                        TECK90

    Exposed to weather        plastic    NMWU
                        TW etc.
                    armor    TECK90

    Direct earth burial/        plastic    NMWU*    UF
    Service entrance            RWU
                        TWU
                    armor    RA90
                        TECK90
                        ACWU90
    [* NMWU not for service entrance]


Subject: Should I use plastic or metal boxes?

    The NEC permits use of plastic boxes with non-metallic cable
    only.  The reasoning is simple -- with armored cable, the box
    itself provides ground conductor continuity.  U.S. plastic
    boxes don't use metal cable clamps.

    The CEC is slightly different.  The CEC never permits cable
    armor as a grounding conductor.  However, you must still
    provide ground continuity for metallic sheath.  The CEC also
    requires grounding of any metal cable clamps on plastic boxes.

    The advantage of plastic boxes is comparatively minor even for
    non-metallic sheathed cable -- you can avoid making one ground
    connection and they sometimes cost a little less.  On the other
    hand, plastic boxes are more vulnerable to impacts.  For
    exposed or shop wiring, metal boxes are probably better.

Subject: Junction box positioning?

    A junction box is a box used only for connecting wires together.

    Junction boxes must be located in such a way that they're accessible
    later.  Ie: not buried under plaster.  Excessive use of junction
    boxes is often a sign of sloppy installation, and inspectors may
    get nasty.

Subject: Can I install a replacement light fixture?

    In general, one can replace fixtures freely, subject to a few
    caveats.  First, of course, one should check the amperage
    rating of the circuit.  If your heart is set on installing half
    a dozen 500 watt floodlights, you may need to run a new wire
    back to the panel box.  But there are some more subtle
    constraints as well.  For example, older house
    wiring doesn't have high-temperature insulation.  The excess
    heat generated by a ceiling-mounted lamp can and will cause the
    insulation to deteriorate and crack, with obvious bad results.
    Some newer fixtures are specifically marked for high
    temperature wire only.  (You may find, in fact, that your
    ceiling wiring already has this problem, in which case
    replacing any devices is a real adventure.)

    Other concerns include providing a suitable ground for some
    fluorescent fixtures, and making sure that the ceiling box and
    its mounting are strong enough to support the weight of a heavy
    chandelier or ceiling fan.  You may need to install a new box
    specifically listed for this purpose.  A 2x4 across the ceiling
    joists makes a good support.  Metal brackets are also available
    that can be fished into ceilings thru the junction box hole and
    mounted between the joists.

    There are special rules for recessed light fixtures such as
    "pot" lamps or heat lamps.  When these are installed in insulated
    ceilings, they can present a very substantial fire hazard.
    The CEC provides for the installation of pot lamps in insulated
    ceilings, provided that the fixture is boxed in a "coffin" (usually
    8'x16"x12" - made by making a pair of joists 12" high, and covering
    with plywood) that doesn't have any insulation.  (Yes, that's 8 *feet*
    long)

    NEC rules are somewhat less stringent.  They require at least 3"
    clearance between the fixture and any sort of thermal insulation.
    The rules also say that one should not obstruct free air movement,
    which means that a CEC-style ``coffin'' might be worthwhile.
    Presumably, that's up to the local inspector.  [The CEC doesn't
    actually mandate the coffin per-se, this seems to be an inspector
    requirement to make absolutely certain that the fixture can't get
    accidentally buried in insulation.  Ie: if you have insulation blown
    in later.]

    There are now fixtures that contain integral thermal cutouts and
    fairly large cases that can be buried directly in insulation.  They are
    usually limited to 75 watt bulbs, and are unfortunately, somewhat
    more expensive than the older types.  Before you use them, you should
    ensure that they have explicit UL or CSA approval for such uses.
    Follow the installation instructions carefully; the prescribed location
    for the sensor can vary.

    There does not yet appear to be a heat lamp fixture that is approved
    for use in insulation.  The "coffin" appears the only legal approach.

Subject: What does it mean when the lights brighten when a motor starts?

    This usually means that the neutral wire in the panel is
    loose.  Depending on the load balance, one hot wire may end up
    being more than 110V, and the other less than 110V, with
    respect to ground.  This is a very hazardous situation - it can
    destroy your electronic equipment, possibly start fires, and in
    some situations electrocute you (ie: some US jurisdictions
    require the stove frame connected to neutral).

    If this happens, contact your electrical authority immediately
    and have them come and check out the problem.

    Note: a brief (< 1 second) brightening is sometimes normal with
    lighting and motors on the same 220V with neutral circuit.  A
    loose main panel neutral will usually show increased brightness
    far longer than one second.  In case of doubt, get help.

Subject: What is 3 phase power?  Should I use it?  Can I get it in my house?

    Three phase power has three "hot" wires, 120 degrees out of
    phase with each other.  These are usually used for large motors
    because it is more "efficient", provides a bit more starting torque,
    and because the motors are simpler and hence cheaper.

    You're most likely to encounter a 3 phase circuit that shows
    110 volts between any hot and ground, and 208 volts between
    any two hots.  The latter shows the difference between a normal
    220V/110V common neutral circuit, which is 240 volts between the
    two hots.  There are 3 phase circuits with different voltages.

    Bringing in a 3 phase feed to your house is usually
    ridiculously expensive, or impossible.  If the equipment you
    want to run has a standard motor mount, it is *MUCH* cheaper to
    buy a new 110V or 220V motor for it.  In some cases it is
    possible to run 3 phase equipment on ordinary power if you have
    a "capacitor start" unit, or use a larger motor as a
    (auto-)generator.  These are tricky, but are a good solution if
    the motor is non-standard size, or too expensive or too big to
    replace.  The Taunton Press book ``The Small Shop'' has an
    article on how to do this if you must.

    Note that you lose any possible electrical efficiency by using
    such a converter.  The laws of thermodynamics guarantee that.

Subject: Is it better to run motors at 110 or 220?

    Theoretically, it doesn't make any difference.  However, there
    is a difference is the amount of power lost in the supply
    wiring.  All things being equal, a 220V motor will lose 4 times
    less power in the house wiring than a 110V motor.  This also
    means that the startup surge loss will be less, and the motor
    will get to speed quicker.  And in some circumstances, the
    smaller power loss will lead to longer motor life.

    This is usually irrelevant unless the supply wires are more
    than 50 feet long.

Subject: What is this nonsense about 3HP on 110V 15A circuits?

    It is a universal physical law that 1 HP is equal to 746
    watts.  Given heating loss, power factor and other inefficiencies,
    it is usually best to consider 1 HP is going to need 1000-1200
    watts.  A 110V 15A circuit can only deliver 1850 watts to a motor,
    so it cannot possibly be more than approximately 2 HP.  Given rational
    efficiency factors, 1.5HP is more like it.

    Some equipment manufacturers (Sears in particular, most router
    manufacturers in general ;-) advertise a HP rating that is far
    in excess of what is possible.  They are giving you a "stall
    horsepower" or similar.  That means the power is measured when
    the motor is just about to stop turning because of the load.
    What they don't mention is that if you kept it in that
    condition for more than a few seconds hopefully your breaker
    will trip, otherwise the motor will melt -- it's drawing far
    more current than it can continuously.

    When comparing motors, compare the continuous horsepower.  This
    should be on the motor nameplate.  If you can't find that figure,
    check the amperage rating, which is always present.

Subject: How do I convert two prong receptacles to three prong?

    Older homes frequently have two-prong receptacles instead
    of the more modern three.  These receptacles have no safety
    ground, and the cabling usually has no ground wire.  Neither
    the NEC or CEC permits installing new 2 prong receptacles anymore.

    There are several different approaches to solving this:
        1) If the wiring is done through conduit or BX, and the
           conduit is continuous back to the panel, you can connect
           the third prong of a new receptacle to the receptacle
           box.  NEC mainly - CEC frowns on this practise.
        2) If there is a copper cold water pipe going nearby, and
           it's continuous to the main house ground point, you can
           run a conductor to it from the third prong.
        3) Run a ground conductor back to the main panel.
        4) Easiest: install a GFCI receptacle.  The ground lug
           should not be connected to anything, but the GFCI
           protection itself will serve instead.  The GFCI
           will also protect downstream (possibly also two prong
           outlets).  If you do this to protect downstream outlets,
           the grounds must not be connected together.  Since it
           wouldn't be connected to a real ground, a wiring fault
           could energize the cases of 3 prong devices connected
           to other outlets.  Be sure, though, that there aren't
           indirect ground plug connections, such as via the sheath
           on BX cable.

    The CEC permits you to replace a two prong receptacle with a three
    prong if you fill the U ground with a non-conducting goop.
    Like caulking compound.  This is not permitted in the NEC.

Subject: Are you sure about GFCIs and ungrounded outlets?
    Should the test button work?

    We're sure about what the NEC and CEC say.  Remember, though,
    that your local codes may vary.  As for the TEST button -- there's
    a resistor connecting the LOAD side of the hot wire to the LINE
    side of the neutral wire when you press the TEST button.  Current
    through this resistor shows up as an imbalance, and trips the GFCI.
    This is a simple, passive, and reliable test, and doesn't require
    a real ground to work.  If your GFCI does not trip when you press
    the TEST button, it is very probably defective or miswired.  Again:
    if the test button doesn't work, something's broken, and potentially
    dangerous.  The problem should be corrected immediately.

    The instructions that come with some GFCIs specify that the ground
    wire must be connected.  We do not know why they say this.  The
    causes may be as mundane as an old instruction sheet, or with the
    formalities of UL or CSA listing -- perhaps the device was never
    tested without the ground wire being connected.  On the other hand,
    UL or CSA approval should only have been granted if the device
    behaves properly in *all* listed applications, including ungrounded
    outlet replacement.  (One of us called Leviton; their GFCIs are
    labeled for installation on grounded circuits only.  The technician
    was surprised to see that; he agreed that the NEC does not require
    it, and promised to investigate.)

Subject: How should I wire my shop?

    As with any other kind of wiring, you need enough power for all
    devices that will be on simultaneously.  The code specifies
    that you should stay under 80% of the nominal capacity of the
    circuit.  For typical home shop use, this means one circuit for
    the major power tools, and possibly one for a dust collector or
    shop vac.  Use at least 12 gauge wire -- many power tools have
    big motors, with a big start-up surge.  If you can, use 20 amp
    breakers (NEC), though CEC requires standard 20A receptacles
    which means you'd have to "replug" all your equipment.  Lights
    should either be on a circuit of their own -- and not shared
    with circuits in the rest of the house -- or be on at least two
    separate circuits.  The idea is that you want to avoid a
    situation where a blade is still spinning at several thousand
    RPM, while you're groping in the dark for the OFF switch.

    Do install lots of outlets.  It's easier to install them in the
    beginning, when you don't have to cut into an existing cable.
    It's useful if at least two circuits are accessible at each
    point, so you can run a shop vac or a compressor at the same
    time as the tool you really want.  But use metal boxes and
    plates, and maybe even metal-sheathed cable; you may have
    objects flying around at high speeds if something goes a bit
    wrong.

    Note that some jurisdictions have a "no horizontal wiring"
    rule in workshops or other unfinished areas that are used
    for working.  What this means is that all wiring must be
    run along structural members.  Ie: stapled to studs.

    Other possible shop circuits include heater circuits, 220V
    circuits for some large tools, and air compressor circuits.
    Don't overload circuits, and don't use extension cords if you
    can help it, unless they're rated for high currents.  (A coiled
    extension cord is not as safe as a straight length of wire of
    the same gauge.  Also, the insulation won't withstand as much
    heat, and heat dissipation is the critical issue.)

    If your shop is located at some remove from your main panel,
    you should probably install a subpanel, and derive your shop
    wiring from it.  If you have young children, you may want to
    equip this panel with a cut-off switch, and possibly a lock.
    If you want to install individual switches to ``safe''
    particular circuits, make sure you get ones rated high enough.
    For example, ordinary light switches are not safely able to
    handle the start-up surge generated by a table saw.  Buy
    ``horsepower-rated'' switches instead.

    Finally, note that most home shops are in garages or unfinished
    basements; hence the NEC requirements for GFCIs apply.  And
    even if you ``know'' that you'd never use one of your shop
    outlets to run a lawn mower, the next owner of your house might
    have a different idea.

    Note: Fine Woodworking magazine often carries articles on shop
    wiring.  April 1992 is one place to start.

Subject: Underground Wiring

    You will need to prepare a trench to specifications, use
    special wire, protect the wire with conduit or special plastic
    tubing and possibly lumber (don't use creosoted lumber, it rots
    thermoplastic insulation and acts as a catalyst in the corrosion
    of lead).  The transition from in-house to underground wire is
    generally via conduit.  All outdoor boxes must be specifically
    listed for the purpose, and contain the appropriate gaskets,
    fittings, etc.  If the location of the box is subject to immersion
    in water, a more serious style of water-proof box is needed.  And
    of course, don't forget the GFCIs.

    The required depths and other details vary from jurisdiction to
    jurisdiction, so we suggest you consult your inspector about
    your specific situation.

    A hint: buy a roll of bright yellow tape that says "buried power
    line" and bury it a few inches above where the wire has been placed.

Subject: Aluminum wiring

    During the 1970's, aluminum (instead of copper) wiring became
    quite popular and was extensively used.  Since that time,
    aluminum wiring has been implicated in a number of house fires,
    and most jurisdictions no longer permit it in new installations.
    We recommend, even if you're allowed to, that do not use it for new
    wiring.

    But don't panic if your house has aluminum wiring.  Aluminum
    wiring, when properly installed, can be just as safe as copper.
    Aluminum wiring is, however, very unforgiving of improper
    installation.  We will cover a bit of the theory behind potential
    problems, and what you can do to make your wiring safe.

    The main problem with aluminum wiring is a phenomenon known as
    "cold creep".  When aluminum wiring warms up, it expands.  When
    it cools down, it contracts.  Unlike copper, when aluminum goes
    through a number of warm/cool cycles it loses a bit of tightness each
    time.  To make the problem worse, aluminum oxidises, or corrodes
    when in contact with certain types of metal, so the resistance
    of the connection goes up.  Which causes it to heat up and corrode/
    oxidize still more.  Eventually the wire may start getting very hot,
    melt the insulation or fixture it's attached to, and possibly even
    cause a fire.

    Since people usually encounter aluminum wiring when they move
    into a house built during the 70's, we will cover basic points of
    safe aluminum wiring.  We suggest that, if you're considering purchasing
    a home with aluminum wiring, or have discovered it later, that you
    hire a licensed electrician or inspector to check over the wiring
    for the following things:

        1) Fixtures (eg: outlets and switches) directly attached to
           aluminum wiring should be rated for it.  The device will
           be stamped with "Al/Cu" or "CO/ALR".  The latter supersedes
           the former, but both are safe.   These fixtures are somewhat
           more expensive than the ordinary ones.

        2) Wires should be properly connected (at least 3/4 way around
           the screw in a clockwise direction).  Connections should be
           tight.  While repeated tightening of the screws can make the
           problem worse, during the inspection it would pay off to snug
           up each connection.

           Note that aluminum wiring is still often used for the
           main service entrance cable.  It should be inspected.

        3) "push-in" terminals are an extreme hazard with aluminum wire.
           Any connections using push-in terminals should be redone with
           the proper screw connections immediately.

        4) There should be no signs of overheating: darkened connections,
           melted insulation, or "baked" fixtures.  Any such damage should
           be repaired.

        5) Connections between aluminum and copper wire need to be
           handled specially.  Current Canadian codes require that the
           wire nut used must be specially marked for connecting
           aluminum to copper.  The NEC requires that the wire be
           connected together using special crimp devices, with an
           anti-oxidant grease.  The tools and materials for the latter
           are quite expensive - not practical to do it yourself unless
           you can rent the tool.

        6) Any non-rated receptacle can be connected to aluminum wiring
           by means of a short copper "pigtail".  See (5) above.

        7) Shows reasonable workmanship: neat wiring, properly stripped
           (not nicked) wire etc.

    If, when considering purchasing a home, an inspection of the wiring
    shows no problems or only one or two, we believe that you can consider
    the wiring safe.  If there are signs of problems in many places,
    we suggest you look elsewhere.  If the wrong receptacles are used,
    you can replace them with the proper type, or use pigtails - having
    this professionally done can range from $3 to $10 per receptacle/switch.
    You can do this yourself too.

Subject: I'm buying a house!  What should I do?

    Congratulations.  But...  It's generally a good idea to hire
    an inspector to look through the house for hidden gotchas.
    Not just for wiring, but plumbing and structural as well.  If an
    inspection of the wiring shows no problems or only one or two minor
    ones, we believe that you can consider the wiring safe (after any
    minor problems are fixed).  If there are signs of problems in many
    places, we suggest you look elsewhere.

    Here's some hints on what to look for:

    Obvious non-code wiring can include:

        - Zip cord wiring, either concealed or nailed to walls
        - Hot wiring on the identified (neutral) conductor without
          proper marking.
        - Ungrounded grounding outlets (except when downstream of
          a GFCI)
        - Splices hanging in mid-air (other than proper knob-and-tube)
        - Switched neutrals
        - Unsecured Romex swinging about like grapevines

    Certain wiring practises that are actually to code (or were at one
    time) sometimes reveal DIY wiring that may have hidden violations:

        - Switches that seem to control nothing (abandoned, perhaps
           not properly terminated wiring)
        - A wall switch that shuts off a group of lights that are
          separately controlled by other wall switches.  (except when
          it's *really* convenient ;-)
        - Switches and outlets in bizarre locations
        - Great numbers of junction boxes without outlets or lamps
        - Junction boxes with great numbers of wires going into them
        - Wiring that passes through a closet instead of a wall or
          ceiling
        - Backwrapped grounding wires

Subject: What is this weird stuff?  Old style wiring

    In the years since Edison "invented" electricity, several different
    wiring "styles" have come and gone.  When you buy an older home you
    may encounter some of this stuff.  This section describes the old
    methods, and some of their idiosyncrasies.

    The oldest wiring system you're likely to encounter is called
    "knob and tube" (K&T).  It is made up of individual conductors with
    a cloth insulation.  The wires are run along side structural
    members (eg: joists or studs) using ceramic stand-offs (knobs).
    Wire is run through structural members using ceramic tubes.  Connections
    were made by twisting the wire together, soldering, and wrapping
    with tape.  Since the hot and neutral were run separately,
    the wiring tends to be rather confusing.  A neutral often runs
    down the centre of each room, with "taps" off to each fixture.
    The hot wire tended to run from one fixture to the next.  In some
    cases K&T isn't colour-coded, so the neutral is often the same
    colour as the hot wires.

    You'll see K&T in homes built as late as the 40's.

    Comments on K&T:

        - the people installing K&T were pretty paranoid about
          electricity, so the workmanship tends to be pretty good.
        - The wire, insulation and insulators tend to stand up
          very well.  Most K&T I've seen, for example, is in
          quite good condition.
        - No grounding.  Grounding is usually difficult to install.
        - boxes are small.  Receptacle replacement (particularly with
          GFCI) can be difficult.  No bushing on boxes either,
          so wiring changes need special attention to box entry.
        - Sometimes the neutral isn't balanced very well between
          separately hot circuits, so it is sometimes possible to
          overload the neutral without exceeding the fusing on
          any circuit.
        - Building code does not permit insulation in walls
          that contain K&T.
        - Connection to existing K&T from new circuits can be
          tricky.  Consult your inspector.
        - Modern wiring practise requires considerably more
          outlets to be installed than K&T systems did.

    Since K&T tends to be in pretty decent condition it generally isn't
    necessary to replace it simply because it's K&T.  What you should
    watch out for is renovations that have interfered with it and
    be cautious about circuit loading.  In many cases it's perfectly
    reasonable to leave existing K&T alone, and add new fixtures on
    new circuits using modern techniques.

    After K&T, they invented multi-conductor cable.  The first type
    you will see is roughly a cloth and varnish insulation.  It looks
    much like the romex cable of the last decade or two.  This stuff was
    used in the 40's and 50's.  Again, no grounding conductor.
    It was installed much like modern wiring.  Its major drawback
    is that this type of insulation embrittles.  We've seen whole
    systems where the insulation would fracture and fall off at
    a touch.  BX cable of the same vintage has similar problems.

    This stuff is very fragile, and becomes rather hazardous if
    the wires become bare.  This wiring should be left untouched as
    much as possible - whenever an opportunity arises, replace it.
    A simple receptacle or switch replacement can turn into a several
    hour long frustrating fight with electrical tape or heat-shrink
    tubing.

    After this wiring technique, the more modern romex was invented.
    It's almost a asphalt impregnated cloth.  Often a bit sticky.
    This stuff stands up reasonably well and doesn't present a hazard
    and is reasonably easy to work with.  It does not need to be
    replaced - it should be considered as safe as the "modern" stuff -
    thermoplastic insulation wire.  Just don't abuse it too much.

Subject: Where do I buy stuff?

    Try to find a proper electrical supply outlet near you.  Their
    prices will often be considerably better than chain hardware stores or
    DIY centres, have better quality materials, have wider variety
    including the "odd" stuff, and have people behind the counter that
    know what you're talking about.  Cultivate friendly knowledgeable
    sales people.  They'll give you much valuable information.
--
Chris Lewis; [e-mail]; Phone: Canada 613 832-0541
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