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Electrical Wiring FAQ (Part 1 of 2)
Section - Surges, spikes, zaps, grounding and your electronics

( Part1 - Part2 - Single Page )
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Top Document: Electrical Wiring FAQ (Part 1 of 2)
Previous Document: How do I convert two prong receptacles to three prong?
Next Document: Are you sure about GFCIs and ungrounded outlets? Should the test button work?
See reader questions & answers on this topic! - Help others by sharing your knowledge

	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

	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

	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

	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.

User Contributions:

Report this comment as inappropriate
Dec 21, 2011 @ 12:00 am
In a fire protection circuit, circuts are shown witha no example 6,8,4etc. what it mean?these circuits are connected between smode detector,junction box etc
Report this comment as inappropriate
Dec 24, 2011 @ 12:12 pm
My daughter dropped a small necklace behind her dresser. The necklace crossed a plug terminal and shorted the receptacle.
I bought a new receptacle and installed the same. I still have no power I suspect there could be a bigger problem,this is aluminum wiring.
I've killed the breaker and call an electrician but am curious as to what happened.P.s. there is a dimmer switch on the same circuit.
Report this comment as inappropriate
Feb 24, 2012 @ 11:11 am
Regarding new construction wiring and running 12/2 and 14/3 wire in the same box.

I have multiple switches to lights. Ran 12/2 and 14/3 into switch box and inspector wrote correction needed.

What should I have done instead?

thank you
Report this comment as inappropriate
Nov 26, 2012 @ 9:21 pm
Does a grounding electrode facilitate the operation of a OCPD, to clear a ground fault ?
Report this comment as inappropriate
Mar 18, 2013 @ 10:10 am
Assuming you are installing two switches in a two switch box, you probably should have used 14/2 and 14/3 instead of replacing 14/2 with 12/2. If you are only installing one switch in a one switch box, you should only have one cable in the box.
P k
Report this comment as inappropriate
Jan 26, 2014 @ 10:10 am
I prefer to use nothing smaller than12 awg /the smallest sized wire on a circuit determines the allowable ampacity
Ex: 15 amp-14awg. 12awg-20amp only rule for thumb other factors such as continuous load,heating and others if you do not know the safe NEC rules then please call a qualified journeyman Electrician better be safe

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Top Document: Electrical Wiring FAQ (Part 1 of 2)
Previous Document: How do I convert two prong receptacles to three prong?
Next Document: Are you sure about GFCIs and ungrounded outlets? Should the test button work?

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Last Update March 27 2014 @ 02:11 PM