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GRHunter 05-25-2011 11:42 AM

Gauge of ground wire
 
Now that I am actually getting into my electric build be prepared for lots of questions in here. :) I am running 240v 30 amp GFCI for my system. As far as power is concerned I know that for 240v that I need 10 gauge wire, and for the 120v leg I only need 14 gauge wire. Now everything is 10 gauge all the way to my brewing control box. But do the ground wires inside my brewing control box and beyond (to my heating element and March pumps) need to follow those same guidelines?

RDWHAHB 05-25-2011 01:05 PM

Definitely wait for an electrition (berniebewer is solid) but I believe you can drop down to #12 for the ground.

Inodoro_Pereyra 05-25-2011 01:23 PM

Quote:

Originally Posted by RDWHAHB (Post 2951623)
I believe you can drop down to #12 for the ground.

You can.
Theoretically, you could use any gauge wire for the ground, as it is supposed to not carry any current, and GFCI's need only a few milliAmps ground current to trip, but, in real life, other considerations make that approach impractical, and eventually dangerous.
For what I've seen, it's common to use the next smaller gauge for the ground wire, in relation with the power wires. So, if you're using #10, a #12 ground is ok.

amb1935 05-25-2011 02:30 PM

This calculates sizes according to NEC
http://www.electrician2.com/calculators/t122_122.html

Walker 05-25-2011 04:42 PM

Quote:

Originally Posted by GRHunter (Post 2951485)
As far as power is concerned I know that for 240v that I need 10 gauge wire, and for the 120v leg I only need 14 gauge wire.

30A service means you are capable of pulling 30A from either of the hot lines. If you are using one of the two hots and the neutral to form a 120V circuit in your panel, it's still a 30A circuit. 120V/30A.

You will need to use 10 gauge wiring there, too, unless you are running that hot line through a breaker or fuse to limit it to 15A or something.

RDWHAHB 05-25-2011 04:50 PM

Quote:

Originally Posted by Walker (Post 2952244)
30A service means you are capable of pulling 30A from either of the hot lines. If you are using one of the two hots and the neutral to form a 120V circuit in your panel, it's still a 30A circuit. 120V/30A.

You will need to use 10 gauge wiring there, too, unless you are running that hot line through a breaker or fuse to limit it to 15A or something.

What he said.

bull8042 05-25-2011 05:25 PM

Walker pretty much answered your question, but I will add: The size of the wire required in a circuit is dictated by CURRENT, not voltage. Also the type on insulation of the conductor. The wire is sized such that the current flowing through it will not cause it to heat beyond what the insulation can stand without melting.
Keep it simple and refer to amb1935's link and let that calculate the wire size properly instead of guessing. It seems to fall in line with NFPA specs.

Walker 05-25-2011 05:28 PM

right. the power cable I use to bring my supply into my control panel is only 8 gauge wiring, but it's got some fancy schmancy insulation on it that allows it to carry 65A.

GRHunter 05-25-2011 06:44 PM

Thanks everyone. Matching the gauge to the amps makes sense. I kind of thought that would be the answer. But I was hoping that it might be possible to use a thinner wire as it is easier to work with inside the enclosure.

Walker 05-25-2011 06:48 PM

Quote:

Originally Posted by GRHunter (Post 2952692)
Thanks everyone. Matching the gauge to the amps makes sense. I kind of thought that would be the answer. But I was hoping that it might be possible to use a thinner wire as it is easier to work with inside the enclosure.

It is a LOT easier to work with thinner wire. That's part of the reason a lot of people put small panel mount breakers or in-line fuses inside the panels. It not only protects the equipment, but lets you work with smaller/easier wiring.

In my panel, I run noe of my hot lines (capable of 50A), through a 15A breaker about the size of a tube of chapstick. After that breaker, I use much smaller wiring for my 120V stuff.


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