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Home Brew Forums > Home Brewing Beer > Electric Brewing > Amp, gauge, duty cycle recommendations
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Old 12-02-2011, 08:48 PM   #11
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Are you planning to use a GFCI breaker in the panel? If not I'd highly recommend it or using a spa panel to add GFCI protection to the circuit. I wouldn't want to touch anything in a e-brewery running at full power without a regularly tested GFCI breaker somewhere upstream from your control panel.

You could install a 30 amp breaker in your panel, run 10 gauge/4 wires to a spa panel ($50 at Home Depot), then run more 10/4 from the spa panel to the control panel. Then you'd have a 30 amp circuit with a neutral available to use if you want to wire in a pump with 120v. That's how I wired up my e-brewery.

EDIT: It looks like Lost snuck in ahead of me with the winning answer.

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Old 12-02-2011, 09:07 PM   #12
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Originally Posted by lazybean View Post
It all depends on your supply. If your plugging into an old dryer outlet that has a 3 wire supply, then you will only have 240 to use. If you have a newer outlet, or are running directly from the panelboard, and have a 4 wire supply then you use the neutral to get your 120v.

If you have the 3wire, and need 120v the easiest option is to just use a second cord to connect to a 120v GFCI, just be sure to keep you circuits separate in your control panel.
Actually, the common 3-wire dryer plugs (NEMA 10 style) are ungrounded. They offer 240V and a neutral, not 240V and a ground. The lights and buzzers on the dryer are usually 120V, and make use of the neutral, and the chassis of the dryer is 'grounded' via the neutral.
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Old 12-02-2011, 10:11 PM   #13
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Originally Posted by bigljd View Post
EDIT: It looks like Lost snuck in ahead of me with the winning answer.
He did, but that's cool. Both answers were totally helpful. The spa panel is clutch. Thanks for pointing that out. GFCI good, zappy bad.

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This is how I wired up my e-brewery.
This is awesome BTW. Probably pretty close to what I'll end up doing. The only difference being that my PID is an Arduino. I have it hooked up to my chest freezer right now and I move it into the garage when I brew to run the HLT. This will be more permanent though so I need to figure out a way to keep the chest freezer happy if I semi-permanently house the Arduino in the garage. I'd just move the freezer out there but then I have to worry about heating it in the winter. The house stays warm enough that I always have it set to cool with no problems.
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Old 12-03-2011, 12:22 AM   #14
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Originally Posted by wyzazz View Post
8Gu is good for 40A so you'd need to move up to 6Gu wire to cover the 50A breaker. 6Gu should be good to 55A.
This is correct, sorry I had a brain fart posting quick at work.

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Old 12-03-2011, 12:43 AM   #15
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I think you are ok with 8 gauge inside the control panel if you are only running 30 amps to the outlet, which you will be if you use a 5500w element.

8 gauge will handle over 50 amps for chasis wiring applications such as this and it will never even see that unless you have a short.

The risk is that the 8 gauge wire will catch fire in the event a short draws all 50 amps through the wire. The thing is, a short will quickly trip the breaker anyway.

The 8 gauge wire is not a fire hazard at 50 amps. Remember the other reason for gauge ratings is voltage drop. 8 gauge results in excess voltage drop in long lines, which is why 6 is needed for power transmission but 8 is ok for chasis wiring.

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Old 12-03-2011, 12:57 AM   #16
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I love pinching pennies as much as the next guy but with something like this I'll spend the extra jing and get the larger gauge wire. Just add on an extra few feet to the wire you're already buying for the run to the outlet and run that in the Control Panel.

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Old 12-03-2011, 03:03 AM   #17
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I respect that position but I would point out that 8 gauge is overdoing it, really you could get away with 10 gauge, that will carry 55amps chasis wiring.

I would also point out that if you plan to use the convenient and cheap 3 wire dryer cord to run from the element(s) to the plug(s) on the control panel then that too is 10 gauge so you'll want to use 6 gauge there too I guess.

Really though, I don't think 10 gauge running even a few feet through open air will burst into flames if 50 amps were briefly run through it. But I am not an electrician.

If you're really that concerned about it, and again I appreciate that position, then you should fuse the 2 240v hot wires as they come into the box. Put a 30 amp fuse on each of the two hot leads. Then you could use 10 gauge around the box and from the box to the elements.

If you haven't priced out wire yet you'll see that the expense of 6 gauge is substantial. It's not just "pinching pennies," more like burning bills. You'll also find that 8 gauge is a b!tch to work with and 6 gauge is even worse.

In the end though you should do what you think is safe because I couldn't live with myself if my bad advice resulted in the serious injury or death of a fellow homebrewer

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Old 12-03-2011, 03:16 AM   #18
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Quote:
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I love pinching pennies as much as the next guy but with something like this I'll spend the extra jing and get the larger gauge wire. Just add on an extra few feet to the wire you're already buying for the run to the outlet and run that in the Control Panel.
I'm totally with you on this one but...hang on now. How many watts are ample to boil a 5 gallon batch? Not sure if I mentioned it but I don't intend on doing more. Let's go with a good rolling 7 gallon maximum boil. Can I get that with a 4500 watt element? If that's the case I can run a 30 amp circuit.
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Old 12-03-2011, 03:31 AM   #19
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I'm totally with you on this one but...hang on now. How many watts are ample to boil a 5 gallon batch? Not sure if I mentioned it but I don't intend on doing more. Let's go with a good rolling 7 gallon maximum boil. Can I get that with a 4500 watt element? If that's the case I can run a 30 amp circuit.
You can easily get it with a 4500W element. Most people around here only have to run a 5500W element at about 60% to get 12 gal boiling nicely. That's 3300W, (averaged over the duty cycle...note that really it's 5500W for 60% of the time, 0W for 40% of the time), and that's 12 gallons.
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Old 12-03-2011, 03:53 AM   #20
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Looking around I found a report at Electrical Wiring Faults – Fire Hazards

It suggests that overloading the wire results in fire when the current is at least 3 times the rating for wire. Here's the quote, "Experimental studies on the gross-overload ignition mode are meager, but they indicate that currents 3 – 7 times the rated load are needed for ignition."

This would indicate that with 10 gauge wire generally rated at around 30 amps, you would have to run at least 90amps through it to generate enough heat to start a fire. Since in practice you'll be running less than 30 amps I think you're fine. If you were to have a short that permitted the full 50 amps through the wire too would be insufficient for a fire (at least one caused by overheating the wire).

Moreover, the 50amp breaker would quickly trip quickly before the wire could heat up anyway. Here's what the article says about that, "In a bolted short, heating is not localized at the fault but distributed over the entire length of the circuit. A bolted short can readily be created by mis-wiring a circuit and then turning on the circuit breaker. The circuit breaker then typically trips before anything ignites. It is, in fact, exceedingly hard to create a fire in branch-circuit wiring from a bolted short."

The other sort of short is an arcing short which creates fire, as you would suspect, by heating and melting the material at the site of the arc. Wire gauge, in the context we are discussing it here (overheating by overloading), would seem to be irrelevant to this sort of short.

More food for thought.

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