Ideal sure test 61-165

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Voltage drop question

Voltage drop question

Speaking of voltage drop, I have a question? I recently took a test that asked the question " According to the NEC what is the recomended allowable voltage drop." Article 210.19 FPN #4 mentions 3% and 5%.
My logic was that 3% would be recomended, but 5% is the allowable. Can anyone give me some feedback or clarification? Thanks.
 
I have yet to see it stated by the NEC, but I too was taught 5% was meant to be max'd in desirable wiring conditions. I was attracted to the tester after finding a TV that had a problem with pulling in and then dropping out on a circuit that had a bad VD problem.
I have some articles on this I will try to find and get back to the forum on it.
 
So, some of you guys are saying that it's normal and fine for your lights to dim when you turn ON your TV set because it's a long run?

You can drop to 107V for 9 cycles on a long distance branch which will dim lights and never see a VD at the panelbox.
 
yrman123 said:
My logic was that 3% would be recomended, but 5% is the allowable. Can anyone give me some feedback or clarification? Thanks.
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That 3% is the "recommended" voltage drop on a "branch circuit" The 5% is total "recommended" voltage drop for the branch circuit 3% and the service cable and feeder 2%.

Unless the service is really loaded or there is a really long distance to the transformer or bad connection you will not see much of a voltage drop at the panel. That's because the service is normally very lighty loaded.

When I said that a certain voltage drop is normal what I ment was this.
All conductors have a certain amount of resistance and there will be a volage drop that will increase with load ( can't be helped ). If you have splices in this conductor ( taps for devices ) the voltage drop should remain almost the same. 100 ft. of cable even if it's been spliced ten times should measure just about the same voltage drop as 100 ft of the same size cable that has not been spliced. You really shouldn't notice the difference. If you pick up a 2% extra voltage drop after a splice then you have a problem. This voltage doesn't just go away it is dissipated as heat. If this heat dissipation occurs in a small area such as a bad connection it may actually cause a fire. A corroded or loose connection is more dangerous than a short because it will not trip a breaker.

This is what I use the Sure Test to look for. If you wanted to use a real load and load up the circuit you could use an IR meter/camera and look for hot spots.
 
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