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I am finishing up installing my generator transfer switch today and I think I have a wiring problem...

I have a six circuit transfer switch wired in with a power inlet box outside. Everything is wired in and I am doing the final check before hooking up the generator. For checking the wiring, I am doing a continuity check between all four conductors. When the transfer switches are all in the "Line" position, I have continuity between neutral-ground and none in the other five combinations (L1-L2, L1-N, L2-N, L1-G, L2-G). With the transfer switches set in the "Off" position, I have the same continuity readings.

The problem (I think) is that when I put the transfer switches in the "Gen" position, I have continuity between every conductor!

I am 99.9999999999% certain this ain't right. Any ideas on where to look first? I am headed back to the basement to open the panel again and double check all the obvious things.

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  • Where are you taking the readings?
    – Tester101
    Commented Nov 21, 2011 at 16:54
  • I am taking the readings from the prongs of the power inlet cord (right where it would plug into the generator). I have removed the cord from the power inlet box and tested it in "free air" and it contains no shorts (and the L1-L2 continuity is present at the power inlet box itself).
    – Dave Nay
    Commented Nov 21, 2011 at 17:10
  • Well now I am even more confused....I moved operations down to the breaker panel and I don't think the problem is with the transfer switch at all. I can't make sense of some things with my breaker panel. (All this was done with mains power disconnected). There are two single-pole breakers where if they are in the "On" position that cause continuity between the two main bus legs of the breaker panel! One of these circuits participates in the transfer switch, but the other one does not.
    – Dave Nay
    Commented Nov 21, 2011 at 18:27
  • Are these breakers stacked (one above the other), or across from each other? Put another way, are they both odd/even (1-3,2-4, etc.), or are they sequential (1-2, 3-4, etc.)? What is on those circuits?
    – Tester101
    Commented Nov 21, 2011 at 18:50
  • @Tester101: They are on opposite sides from each other, but not directly across. I will have to check to see if they are on the same leg or not.
    – Dave Nay
    Commented Nov 21, 2011 at 18:57

1 Answer 1

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If you are testing continuity at the generator inlet plug with the transfer switch in the GEN. position, you will be measuring continuity throughout the entire circuit. If you look at this image, you should see why you're getting the readings you are.

enter image description here

The light blue box on the left, represents the main service panel. The light blue box on the right, represents the transfer switch.

Have the installation inspected by a certified licensed electrician before using the generator, to make sure the transfer switch is installed properly. Remember, peoples lives could be on the line here (pun intended). Back feeding caused by improper transfer installation, can kill linesmen trying to restore electrical service to your home during an outage.

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  • Errr...I guess that was an I.D. 10-T error on my part then, because that makes perfect sense that there has to be continuity between L1/L2 and Neutral, otherwise there would be a completely open circuit and nothing would work. Would it be correct to say that the continuity between L1 and L2 is caused by the inductive load of my 240v well pump? Seeing it drawn out make it much clearer, thanks.
    – Dave Nay
    Commented Nov 21, 2011 at 18:44
  • @DaveNay yes, if you have a 240V device wired to the transfer switch you may indeed see conductivity between L1-L2.
    – Tester101
    Commented Nov 21, 2011 at 18:47

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