Ground Wire Gauge - Fiberglass RV


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Old 04-23-2014, 07:07 AM   #1
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Ground Wire Gauge

Is there a rule of thumb to determine what gauge the ground wire should be both in the trailer and through the harness?
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Old 04-23-2014, 08:00 AM   #2
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10 gauge is typical.
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Old 04-24-2014, 05:26 AM   #3
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Is this a safety issue? Would 12 gauge cut it?
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Old 04-24-2014, 06:32 AM   #4
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Very good question. Here is simple quote...".. Remember that common ground wires must be adequate to carry the TOTAL amperage of the circuit, even when separate hot wires are used..."...
Wire Gauge Specification - TECHNICAL REFERENCE
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Old 04-24-2014, 07:00 AM   #5
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Thank you! There's my answer!
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Old 04-24-2014, 07:28 AM   #6
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You question can be answered with as much complication as you desire. If you’re looking for a simple, no-thought answer I think 10 ga. is a good one.

In general (and I’m no EE) you get to make your first decision as to how much voltage drop you want to tolerate. Voltage drop is a function of wire gauge, round trip wire length and amperage. There are all sorts of tables and calculators to help determine what wire gauge to use. West Marine has one I use, mostly because I’ve had a sailboat for longer than I’ve had the trailer. I generally shoot for 3% drop in the 12V side. Why? No reason. I did more boondocking in the past and I wanted as little loss as practical without going into room temperature superconductors. From the table, assuming a 32 foot round trip (I have a Casita 16’ SD) and 10 amps moving to the trailer from the tow, then that puts me right in the green band, or 10 ga.

I have one circuit I have fused for 20 amps that supplies the macerator pump I sometimes use to dump uphill or to speed the dump process. The outlet for that is right behind the fuse panel on the streetside of the trailer. Round trip length of inside and outside wiring is about 12-14 feet. That puts me again in the 10 ga band which is what I used.

Do you need 3% drop? No. Paraphrasing the Gallagher routine, it’s about style. Just watch out for the Sledge-O-Matic and the exploding watermelon…
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Old 04-24-2014, 09:39 AM   #7
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Again, thanks.
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Old 04-24-2014, 09:45 AM   #8
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Originally Posted by Steve L. View Post
You question can be answered with as much complication as you desire. If you’re looking for a simple, no-thought answer I think 10 ga. is a good one.

In general (and I’m no EE) you get to make your first decision as to how much voltage drop you want to tolerate. Voltage drop is a function of wire gauge, round trip wire length and amperage. There are all sorts of tables and calculators to help determine what wire gauge to use. West Marine has one I use, mostly because I’ve had a sailboat for longer than I’ve had the trailer. I generally shoot for 3% drop in the 12V side. Why? No reason. I did more boondocking in the past and I wanted as little loss as practical without going into room temperature superconductors. From the table, assuming a 32 foot round trip (I have a Casita 16’ SD) and 10 amps moving to the trailer from the tow, then that puts me right in the green band, or 10 ga.

I have one circuit I have fused for 20 amps that supplies the macerator pump I sometimes use to dump uphill or to speed the dump process. The outlet for that is right behind the fuse panel on the streetside of the trailer. Round trip length of inside and outside wiring is about 12-14 feet. That puts me again in the 10 ga band which is what I used.

Do you need 3% drop? No. Paraphrasing the Gallagher routine, it’s about style. Just watch out for the Sledge-O-Matic and the exploding watermelon…
'll

The 3% voltage drop rule is a standard from the NEC .The NEC has rules for allowable % voltage drop for both feeders and branch circuits. A # 10 AWG
is sufficient based on voltage drop ,ampacity and mechanical strength. Using a larger gauge wire in many cases does nothing but increase the cost.
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Old 04-24-2014, 10:39 AM   #9
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Originally Posted by steve dunham View Post
'll

The 3% voltage drop rule is a standard from the NEC .The NEC has rules for allowable % voltage drop for both feeders and branch circuits. A # 10 AWG
is sufficient based on voltage drop ,ampacity and mechanical strength. Using a larger gauge wire in many cases does nothing but increase the cost.
Cool! I love it when I do the right thing for the wrong reason. Sort of offsets the karma of those doing the wrong thing for no reason...
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