From: clewis@ferret.ocunix.on.ca (Chris Lewis)
Newsgroups: misc.consumers.house,rec.woodworking,news.answers
Subject: Electrical Wiring FAQ
Summary: A series of questions and answers about house wiring
Date: 29 Jul 92 07:29:16 GMT
Expires: 26 Aug 92 07:28:54 GMT
Reply-To: wirefaq@ferret.ocunix.on.ca (Wiring FAQ commentary reception)
Followup-To: poster
Organization: Elegant Communications Inc., Ottawa, Canada
Supersedes: <wirefaq_711168413@ecicrl>

Archive-name: electrical-wiring
Last-modified: Tue Jul 14 21:31:56 EDT 1992

	    Frequently Asked Questions on Electrical Wiring

		Steven Bellovin (smb@ulysses.att.com)
		Chris Lewis (clewis@ferret.ocunix.on.ca)

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

Major overhaul this go-round.  It was Steven's turn ;-)

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.

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 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.
	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?
	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? (NEW)
	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? (NEW)
	    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).
	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''.

	And finally: 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.

	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.  If you
	impress the inspector on the first bit of wiring checked, the
	remainder will probably only be glanced at.

	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.

|	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 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 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: 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.  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.

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.

	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 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.

Subject: Where should GFCIs be used?

	The NEC mandates GFCIs for 120V, 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 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.

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: 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
	(NEC) or NMD90 (CEC).  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/NMD90.
	
	Where the wire is subject to damage (ie: closer than 1 1/4" of
	the face of the stud, on the surface of walls below 5 feet, on
	the bottoms of rafters in low sections of an attic), the wire
	has to be protected.  BX cable -- technically known as AC (AC90 CEC)
	-- has a aluminum or steel sheath over the conductors and is fairly
	resistant to damage.  In some cases you can use a metal plate
	or length of flexible conduit instead (like BX, but no wires
	inside) to protect the wire where it is exposed.  This is most
	often found when the wire to a furnace or water heater has to
	"hop" from the wall to the equipment.  BX cable, or a short length
	of flexible conduit is used to protect the wire where it's suspended.

	When run along the bottom of joists, BX must be installed 1.25"
	below the surface (NEC).

	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.

 	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.

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?

	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.

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.
|	[I could have sworn I saw something about a coffin, but I haven't
|	been able to find it. (Steven)]

|	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 third prong
	       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.

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.

	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).  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.

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; clewis@ferret.ocunix.on.ca; Phone: Canada 613 832-0541
Psroff 3.0 info: psroff-request@ferret.ocunix.on.ca
Ferret list: ferret-request@ferret.ocunix.on.ca