#10 Earth with #8 Hot Wires (240V / 60A) ??

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drizzy

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I hired a contractor to install a 240V / 60A feed to a spa. The spa company specifies "AWG 8 wiring" (2-wire with earth). The contractor used #8 black and red wires for the hots, but #10 for the green ground. Is that OK?
 
drizzy said:
I hired a contractor to install a 240V / 60A feed to a spa. The spa company specifies "AWG 8 wiring" (2-wire with earth). The contractor used #8 black and red wires for the hots, but #10 for the green ground. Is that OK?
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I don't know why some of the spa mfg state to use a larger ground than is required by the NEC. What the contractor did was safe and allowed by the code (NEC). Now as far as the mfg specs, that could affect the warranty should something happen. Even though it probably wouldn't have anything to do with a problem, they could use the fact that they required a larger ground, but a smaller one was installed, to deny a claim.
 
Bill, can you elaborate a little bit on this? When I do a calculation here: http://www.csgnetwork.com/wiresizecalc.html ... it says that a 140 foot run @ 240V 60A single phase requires #8. Now, I'm pretty sure that the full current flows through the green ground wire to both hots, otherwise there would be no circuit. And if that's the case, then why would a current-carrying line (ground) not be required to be #8, just like the hot wires?
 
drizzy said:
Now, I'm pretty sure that the full current flows through the green ground wire to both hots, otherwise there would be no circuit. And if that's the case, then why would a current-carrying line (ground) not be required to be #8, just like the hot wires?
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Heres the short of it- your 240v equipment doesn't require a neutral, so there is no other wire that returns anything- the amount of current on each of the hots will be identical, so there is no imbalance (neutral current) that needs to return to the source .That green wire is called an equipment grounding conductor, it won't normally carry anything except in the advent of a fault.
 
drizzy said:
Bill, can you elaborate a little bit on this? When I do a calculation here: http://www.csgnetwork.com/wiresizecalc.html ... it says that a 140 foot run @ 240V 60A single phase requires #8. Now, I'm pretty sure that the full current flows through the green ground wire to both hots, otherwise there would be no circuit. And if that's the case, then why would a current-carrying line (ground) not be required to be #8, just like the hot wires?
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The circuit is completed across the two hots. There is no current flowing on the equipment ground unless there is a fault.

10AWG is all that is required by the NEC for a 60A overcurrent protection device per 250.122. Your only gripe with your contractor is that he did not follow the manufacturer's instructions.
 
drizzy said:
Bill, can you elaborate a little bit on this? When I do a calculation here: http://www.csgnetwork.com/wiresizecalc.html ... it says that a 140 foot run @ 240V 60A single phase requires #8. Now, I'm pretty sure that the full current flows through the green ground wire to both hots, otherwise there would be no circuit. And if that's the case, then why would a current-carrying line (ground) not be required to be #8, just like the hot wires?
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First we are not talking about voltage drop, which is what you got from the link.

2nd, your OP said the feed was to a 60A disconnect. The #8 required by the mfg would only be a 50A, possibly a 40A. Just because the disconnect is rated at 60A doesn't mean that's what the circuit is.

The rest of the posts explain about the ground, it does not carry current.
 
Little Bill said:
The rest of the posts explain about the ground, it does not carry current.
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Thanks, everyone. I get it now. The twin 120V feeds are "differential" which is its own "floating" reference. The common is the center tap at the pole transformer, and not used for 240V two-wire current conduction. And the green ground is earth.
 
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