Archive-name: electrical-wiring/part1
Last-modified: Tue Jun 14 00:35:39 EDT 1994

     Frequently Asked Questions on Electrical Wiring

                        Copyright 1991, 1992, 1993
  Steven Bellovin (smb@research.att.com)
  Chris Lewis (clewis@ferret.ocunix.on.ca)

  Redistribution for profit, or in altered content/format
  prohibited without permission of the authors.  Any other
  redistribution must include this copyright notice and
  attribution.

     Comments to (automatic if you reply to this article):
      wirefaq@ferret.ocunix.on.ca

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
house-archive@dg-rtp.dg.com for information.

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

------------------------------
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?
 What impact does NAFTA have on wiring standards and approvals?
 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
 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
 How do I convert two prong receptacles to three prong?
 Surges, spikes, zaps, grounding and your electronics
 Are you sure about GFCIs and ungrounded outlets?
     Should the test button work?
 What kind of outlets do I need in a kitchen?
 Where must outlets and switches be in bathrooms?
 General outlet placement rules/line capacities
 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?
 Noisy fluorescent fixtures, what do I do?
 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 should I wire my shop?
 Underground wiring
 Doorbell/telephone/cable other service wiring hints
 Aluminum wiring
 I'm buying a house!  What should I do?
 What is this weird stuff?  Old style wiring
 Where do I buy stuff?
 Copper wire characteristics table

------------------------------
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 has been released.
 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.  Apparently Stanley
 utility knives fitted with linoleum cutters (hooked blades)
 can be used to strip sheath, but there is still the possibility
 that you'll gouge 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".  It used to be
 an Insurance Industry organization, but now it is independent
 and non-profit.  It 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-listed 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-listed device.  Furthermore, in
 many situations the NEC will require that a wiring component
 used for a specific purpose is UL-listed for that purpose.
 Indirectly, this means that certain parts of your wiring
 must be UL-listed before an inspector will approve it and/or
 occupancy permits issued.
 
------------------------------
Subject: What is CSA approval?

 Every electrical device or component must be certified by the
| Canadian Standards Association (or recognized equivalent) 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 (or
 recognized equivalent) 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.

 Note: strictly speaking, there usually is a legal way around
 the lack of a CSA sticker.  In some cases (eg: Ontario), a
 local hydro inspection prior to purchase, or prior to use, is
 acceptable.  The hydro inspector will affix a "hydro sticker"
 to the unit, which is as good as CSA approval.  But it costs
 money - last I knew, $75 per unit inspected.

 ULC (Underwriters Laboratory of Canada) is an independent
 organization that, amongst other things, undertakes the
 quarterly inspection of manufacturer's to ensure continued
 compliance of UL Listed/Recognized products to Agency reports
 and safety standards. This work is done under contract to UL
 Inc (Follow-up Services Division). They are not a branch or
 subsidiary of UL.

------------------------------
Subject: What impact does NAFTA have on wiring standards and approvals?

 The North America Free Trade Agreement came into effect on
 January 1st, 1994.  NAFTA attempts to bring down trade barriers
 between Mexico, Canada and the USA.  One of the "barriers" has
 been that of approval of material.  As of January first, CSA
 approval of a device is legally considered equivalent to UL
 approval in the USA.  Conversely, UL is now accepted as
 equivalent to CSA approval in Canada.  Theoretically, this
 means that devices marked only with UL approval are acceptable
 in the CEC, and conversely CSA approval by itself of a device
 is accepted by the NEC.  This allows much freer trade in
 electrical materials between the two countries.

 This doesn't affect the electrical codes themselves, so the
 differences in practice between the NEC and CEC will remain.
 It is also my understanding that bilateral acceptance of
 "approval" will only apply when the standards applied are
 reasonably the same.  As an example, a cable approved by the
 NEC for a given purpose may not be acceptable by the CEC for
 the same purpose if the standards requirements are different.
 Eg: "NMD" ("non-metallic, damp") cable is usually required for
 residences in Canada.  "NM" cable ("non-metallic, not damp
 locations) which is used in the same situations in the US,
 would probably not be acceptable in Canada.  Also,
 municipalities can add additional requirements on top of the
 CEC, as they can in the US over the NEC.

 Thus, Canadians will probably start seeing UL-only approved
 materials in stores, and Americans the same regarding
 CSA-only.  But some differences will remain.  When in doubt on
 major items, consult an inspector.  At least in Canada, the
 fact that the material is available in a store usually means
 that it's okay to install.

------------------------------
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 1993.

 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

 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 +- 5% legs.  Additionally, 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.

 One thing that might make this a little more understandable
 is that the nameplates on equipment ofen show the lower (ie: 110V
 instead of 120V) value.  What this implies is that the device
 is designed to operate properly when the voltage drops that
 low.

 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.   480V is the voltage between phases of a 3-phase "Y"
 circuit that's 277V from hot to neutral.

 In keeping with 110V versus 120V strangeness, motors intended
 to run on 480V three phase are often labelled as 440V...

------------------------------
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 or green with a yellow stripe 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.]

 Note: do not tape, colour or substitute other colour wires for the
 safety grounding conductor.

 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.
 [This author has seen it happen.]  Breakers won'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, wet-bar
 sinks, roof outlets, 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 NEC now requires that if your replace an outlet in a
 location now requiring GFCI, you must install GFCI protection.
 Note in particular - kitchen and bathroom outlets.

 When using the "fixed appliance" rule for avoiding GFCI outlets,
 single outlet receptacles must be used for single appliances,
 duplex receptacles may be used for two 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,
 as do pools systems and jacuzzi or whirlpool pumps.

 There are many rules about GFCIs with pools and so on.  This
 is outside of our expertise, so we're not covering it in
 detail.  See your inspector.

 When replacing an outlet, it must now be GFCI-protected if
 such would now be required for a new installation.  That is,
 a kitchen outlet installed per the 1984 code need not have
 been protected, but if that outlet is ever replaced, GFCI
 protection must now be added (under NEC).  This is explicit
 in the 1993 NEC, and inspector-imposed in Canada.

 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.

 Note that the labels are mandatory for GFCI-protected-but-ungrounded
 three prong outlets according to the NEC.

------------------------------
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: 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 practice.
     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.
        NEC: this can only be done if the point of attachment
        is within 5 feet of where the pipe enters the ground.
     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.

 The NEC requires that three prong receptacles without ground
 that are protected by GFCI must be labelled as such.

 See the next section about computers on GFCI-protected groundless
 outlets.

------------------------------
Subject: Surges, spikes, zaps, grounding and your electronics

 Theoretically, the power coming into your house is a perfect AC
 sine wave.  It is usually quite close.  But occasionally, it
 won't be.  Lightning strikes and other events will affect the
 power.  These usually fall into two general categories: very
 high voltage spikes (often into 1000s of volts, but usually
 only a few microseconds in length) or surges (longer duration,
 but usually much lower voltage).

 Most of your electrical equipment, motors, transformer-operated
 electronics, lights, etc., won't even notice these one-shot
 events.  However, certain types of solid-state electronics,
 particularly computers with switching power supplies and MOS
 semiconductors, can be damaged by these occurances.  For
 example, a spike can "punch a hole" through an insulating layer
 in a MOS device (such as that several hundred dollar 386 CPU),
 thereby destroying it.

 The traditional approach to protecting your electronics is to
 use "surge suppressors" or "line filters".  These are usually
 devices that you plug in between the outlet and your
 electronics.

 Roughly speaking, surge suppressors work by detecting
 overvoltages, and shorting them out.  Think of them as voltage
 limiters.  Line filters usually use frequency-dependent
 circuits (inductors, capacitors etc.) to "tune out" undesirable
 spikes - preventing them from reaching your electronics.

 So, you should consider using suppressors or filters on your
 sensitive equipment.

 These devices come in a very wide price range.  From a couple
 of dollars to several hundred.  We believe that you can protect
 your equipment from the vast majority of power problems by
 selecting devices in the $20-50 range.

 A word about grounding: most suppressors and EFI filters
 require real grounds.  Any that don't are next to useless.

 For example, most surge suppressors use MOVs (metal oxide
 varistors) to "clamp" overvoltages.  Yes, you can have a
 suppressor that only has a MOV between neutral and hot to
 combat differential-mode voltage excursions, but that isn't
 enough.  You need common-mode protection too.  Good suppressors
 should have 3 MOVs, one between each pair of wires.  Which
 means you should have a good solid ground.  Eg: a solidly
 connected 14ga wire back to the panel.  Not rusty BX armour or
 galvanized pipe with condensation turning the copper connection
 green.

 Without a ground, a surge or spike is free to "lift" your
 entire electronics system well away from ground.  Which is
 ideal for blowing out interface electronics for printer ports
 etc.

 Secondly, static electricity is one of the major enemies of
 electronics.  Having good frame grounds is one way of
 protecting against static zaps.

 If you're in the situation of wanting to install computer
 equipment on two wire groundless circuits take note:

 Adding a GFCI outlet to the circuit makes the circuit safe for
 you.  But it doesn't make it safe for your equipment - you need
 a ground to make surge suppressors or line filters effective.

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

 The NEC, section 210-7(d), and CEC, section 26-700(9), are quite
 explicit that GFCIs are a legal substitute for a grounded outlet
 in an existing installation where there is no ground available in
 the outlet box.

 But 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.)

-- 
Chris Lewis: _Una confibula non sat est_
Phone: Canada 613 832-0541  Ferret list: ferret-request@ferret.ocunix.on.ca
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