Neutral and ground wire size from generator

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Old 08-15-12, 12:56 PM
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Neutral and ground wire size from generator

I'm installing a 7 Kw pad generator and the recomended minimum wire size is 10 AWG. I think I want to use 8 AWG for the 50 foot lengh to reduce voltage loss.

The generator has a two pole 30 amp breaker to feed to my transferr switch. Most of my loads will be 110 volt so will the neutral wire carry 60 amps if I'm at maximum load? There is a ground (green) wire also in the feed. Does that ground wire carry any of the load from the neutral wire?
 
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Old 08-15-12, 01:13 PM
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The green grounding conductor should only carry current in the event of a fault.

The neutral will carry the difference in current between the two hots. For example, one leg carries 15 amps and the other hot carries 25. The neutral will only see ten amps.
 
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Old 08-15-12, 01:17 PM
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Welcome to the forums!

I'm installing a 7 Kw pad generator and the recomended minimum wire size is 10 AWG. I think I want to use 8 AWG for the 50 foot lengh to reduce voltage loss.
There should be almost no voltage drop (voltage is never really lost) in a 50' run. Not only is 10AWG rated for 30A, and less expensive, it also offers less resistance than 8AWG.

The generator has a two pole 30 amp breaker to feed to my transferr switch. Most of my loads will be 110 volt so will the neutral wire carry 60 amps if I'm at maximum load?
Your power supply is single-phase 240V. It is carried on two split-phase legs. Connecting either of those legs through a device to a grounded conductor (a neutral) gives a potential of 120V. There is no "110V" in the US. Re 60A on the neutral wire - No.

There is a ground (green) wire also in the feed. Does that ground wire carry any of the load from the neutral wire?
Not unless there's a wiring fault somewhere.

Wiring Simplified is a valuable resource for learning more about residential electrical systems. It's also inexpensive and available in the electrical aisle at many home improvement centers.
 
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Old 08-15-12, 01:28 PM
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my generator back feed has 120 feet of 10/3g, and ran the house fine. I have a you-tube video of it running the house for 7 days when we had the power outage on halloween in 2011. You would think you would get 60 amps , but i guess when one phase is up, the other is down, so you get only 30 amps i think total from each leg, etc. So, if any one of the legs are over 30A, it will trip both i think.
 
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Old 08-15-12, 01:33 PM
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Thanks. I was guessing it could not be 60 amps. So since the currents are out of phase it cancels.

Yes, I meant to say 120 volts. I'm old school and 240,220, 120, 115 and 110 volt were pretty common terms.

Computing voltage drop. Would it be 100 foot of #10 wire since the circuit has to complet both legs?
 
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Old 08-15-12, 01:46 PM
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Would it be 100 foot of #10 wire since the circuit has to complet both legs?
Before it encounters a load? No, the distance is the straight-run distance.

So since the currents are out of phase it cancels.
I think you'll really enjoy reading Wiring Simplified.
 
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Old 08-15-12, 04:09 PM
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Voltage drop is figured on the out and back distance. If you had a receptacle 50' from a panel you would use 100' in the VD calculation.
 
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Old 08-15-12, 06:09 PM
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I ran the numbers at 30 amps. 100 foot of 10 AWG would be 3 volt drop. 100 foot of 8 AWG would be 1.89 volt drop. Looks like 10 AWG will work fine

10 AWG will loose 90 watts and 8 AWG will loose 57 watts at 30 amps.
 
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Old 08-22-12, 11:48 AM
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Looks like Generac has changed from 4 control wires to 6. Lucky I saw this before making my cable to the transfer switch. They now want 120 volts feed to the generator (Neutal line) and they feed back battery (+12 volts) to the switch.
 
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Old 11-29-12, 10:23 PM
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I also like the Wiring Simplified book. I learned much if not most of what I know about residential wiring from this book. I always get the newest edition when it comes out.
 
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