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Electrical Wiring FAQ (Part 2 of 2)
Section - What is this nonsense about 3HP on 110V 15A circuits?

( Part1 - Part2 - Single Page )
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Top Document: Electrical Wiring FAQ (Part 2 of 2)
Previous Document: Is it better to run motors at 110 or 220?
Next Document: How should I wire my shop?
See reader questions & answers on this topic! - Help others by sharing your knowledge

	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 your motor will melt - the
	motor is drawing far more current than its continuous rating.

	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.

User Contributions:

Dev
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
kevin
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.
dennis
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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
dennis
Robert
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Nov 26, 2012 @ 9:21 pm
Does a grounding electrode facilitate the operation of a OCPD, to clear a ground fault ?
@dennis
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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 2 of 2)
Previous Document: Is it better to run motors at 110 or 220?
Next Document: How should I wire my shop?

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Last Update March 27 2014 @ 02:11 PM