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

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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
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
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
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
Nov 26, 2012 @ 9:21 pm
Does a grounding electrode facilitate the operation of a OCPD, to clear a ground fault ?
@dennis
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
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
Robert
Sep 11, 2014 @ 6:18 pm
Someone wrote this:
"Don't bother asking in Quebec - DIY wiring is banned throughout
the province."

The statement above is not true.
You can do anything you want as long as you follow the electrical code... just like in any other province.
Not following the code may not technically make you unsafe in the real world, but it may nullify you insurance claims if your house burns down because of your sloppy work. If you're not sure, get an expert to sign off on it. ;-)

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