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Tweakers' Asylum Tweaks for systems, rooms and Do It Yourself (DIY) help. FAQ. |
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In Reply to: AC Mains question posted by sailor321 on July 6, 2005 at 11:24:18:
First let me say I would like to find something in the code book but have not as of yet. The best I have found so far is maximum allowable voltage drop from your panel to any outlet is listed as 3% and from pole to any outlet is listed as 5%.But let's look at this is a different way. For a 20 amp breaker you would be required to have #12 wire and for houshold breakers that 20 amp breaker is only allowed to carry a maximum current of 16 amps (household breakers are only 80% rated). #12 wire has a resistance of 1.7 ohms per 1,000 feet. Let's say the maximum wire distance from breaker panel to outlet is 200 feet which I think will cover most homes. And let's say the maximum current that this #12 wire would see is 16 amps. So, the wire with have a resistance of 0.34 ohms for 200 feet of it and when 16 amps of current is passed through it a voltage drop of 5.44 volts will occur. If we call the voltage 120VAC and go with the 3% rule then we are looking at a voltage drop of 3.6VAC. I would err on the side of caution and like not to see over a 3.6VAC difference between neutral and ground but wouldn't be concerned with a 5.44 difference on a heavily loaded circuit at the farthest point from the panel. All of that said I commonly see readings in the neighborhood of 1/2 volt between neutral and ground at the outlet with some load in place.
I hope this makes some sense and helps to answer your question(s).
For more electrical info check out Mike Holt's web site.
Russ
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Follow Ups
- This is how I would look at it - Russ57 10:16:54 07/08/05 (0)
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