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Old 09-20-2011, 09:44 PM   #1
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I am going to install a 14kw generator and ATS at my home The generator will be located 85 ft from the ATS on the ATS is within a foot from the main panel. The generator will be located about 15 ft from my house to meet the 10 ft distance from LPG and 5 ft from combustibles code requirement here in New Hampshire.

First I am not sure what size wire I need to use because I need to bury the feed between the gen and the house Best I can tell I can use 8 AWG for the 50 amp service as long as I don't have to de-rate the cable for the short 10 ft distance otherwise I need 6 AWG. Do I have to de-rate the cable and can I run UF cable through my basement to the ATS in open air by cable clipping it to the rafters overhead? If I have to run end-to-end in conduit can i use liquid-tight for the outside portion and PVC once I am inside. Also, is liquid-tight considered to be the same as steel conduit? NH code says I have to bury cable that is un-protected or run in PVC 18" or deeper but cable run through steel conduit or encased in 4" of concrete only needs to be 6" deep.

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Old 09-20-2011, 10:50 PM   #2
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I would use #6 for that run from the generator to the transfer switch, assuming it is 85'. Your 14k generator is good for 60 amp @ 240v. You said 50 amp service....is that what the generator breaker is? I'm a bit confused...you have 85, 15 and 10 feet in your post. Not exactly sure what it is you are doing. Remember that the breaker protects the wiring, and some excessive lengts will decrease voltage. Imagine a funnel...no matter how much you pour into it, the same amount will always come out due to decreased size of the outlet. Too small a wire will basically have the same effect.

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Old 09-21-2011, 12:51 AM   #3
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Sorry for the confusion. The total length of the run is 85 ft. The distance of the underground portion is 15 ft and the indoor portion is 70 ft. For a total of 85 ft. As for the current, the main output breaker on the gen is rated at 50 amps.

I guess my main concerns are if liquid-tight is considered to be the same as steel conduit and if it is permitted to run exposed UF cable along my basement ceiling rafters? I am trying to avoid running PVC from the point the run enters my home to the ATS. If I am required to use conduit end-to-end I will need to use THWN cable to avoid wresteling with 6 AWG UF cable in conduit. Using THWN and PVC conduit will add to the cost and will take longer to install.

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Old 09-21-2011, 11:19 AM   #4
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UF is rated for direct burial, so you could just bury it unprotected at 18 inches if your code allows that.

I see no need for an end to end conduit run. UF can be used indoors, treat it with the same rules as NM/Romex.

Liquidtight is Flexible Metal Conduit which is not the same as rigid metal conduit. It most likely does not qualify for a 6 inch exception in your state, those are almost always rigid-only. And even if it did, do you really want to do that? 6 inches is a misplaced hand shovel stroke away from being crushed.

I would either go with UF directly buried with 90 degree PVC pipes only on the ends, or with the liquidtight/THWN transistioning to NM once it's indoors with a junction box.

Also heed what Missouri said, you really should upsize the conductor to #6. Generators are saggy enough voltage wise without you dropping more in a long wire run.
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Old 11-16-2011, 12:51 PM   #5
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I am going through a similar setup. 7KW unit with 8 circuit transfer switch.
Generator is 5 feet from the house and then 40 feet in basement to transfer switch which is 3 feet from main panelboard.
I plan on using liquid tite from genset with THWN wire to junction box inside basement, then romex across to transfer switch. I also plan to run the transfer switch control wires the same way. My generator has an external breaker on it so I assume that will serve as a disconnect in meeting code. If not I will put a disconnect on the outside wall of the house. I also am going to have to get an electrician as my town will not issue an electrical permit to a homeowner.
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