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I bought a new 240v homebrew system. The system requires a 30 amp circuit and comes with 10 gauge wires (black, white, green) but no plug (so you can connect the plug needed for your situation).

I also recently bought an electric vehicle so I had a 14-50R installed in my garage with a 50 amp GFCI breaker.

I want to connect my system to the 14-50R, so I bought a 14-50P to connect to the bare wires from the system. The issue I have is that the 14-50P has 4 terminals (2 hot, 1 neutral and 1 ground), but there are only three 10 gauge wires coming out of my 240v system (1 hot, 1 neutral and 1 ground). The terminals in my 14-50P are removable, so should I connect the 1 hot, ground and neutral and remove the unused hot terminal? Or should I do something totally different? And am I okay using the 10 gauge wire since the system will only draw less than 30 amps?

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Well, four prongs, three wires: that's 24 possibilities. Should take you a couple of hours to try them all, plus a few minutes to call the fire department ;) – Daniel Griscom Feb 25 at 19:49
    
I'd like to avoid that last part! :) – meis1212 Feb 25 at 19:52
    
Did the system come with installation instructions from the manufacturer? – Tester101 Feb 25 at 21:15
up vote 4 down vote accepted

If it's 240 volt it doesn't have a neutral. So your home brew has 2 hots and a ground.

Just wire it with the reverse pattern of the receptacle except for the neutral (white) wire will be deleted from the plug.

10 gauge is good for 30 amps but understand the receptacle is protected with a 50 amp breaker so if your homebrew has a recommended max size breaker less than that you will be exceeding the recommended protection for your brewer.

Good luck!

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@Aron he was clearly speaking in the context of the question which was an american device with only three wires and specified as 240V. – Peter Green Feb 26 at 1:32
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It is fine to plug in to the 50 amp receptacle if your home brew draws 30 amps or less. Meaning the current draw on the label. I just meant that if the manufacturer recommends the circuit to be protected at 30 amps than you will be exceeding that recommendation. This is usually not a problem as long as the cord is short. Like not a 100' long extension cord. – ArchonOSX Feb 26 at 1:34
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@Aron #1) European voltage is 220 not 240. #2) you can't get 208volts on a delta system that is a 3 phase wye system. #3) single family residential systems are single phase 3 wire and #4) there is no such thing as single phase delta that would be a complete contradiction since a delta system is 3 phase by definition. – ArchonOSX Feb 26 at 1:56
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@Aron -- neither nor -- the entire distribution transformer in a US residential environs is 1ph MV (say 8kV) to 1ph 240/120V LV (120-0-120, with the center tap both earthed and distributed as the service neutral) – ThreePhaseEel Feb 26 at 5:45
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This comment thread is the most simultaneously annoying and educational thing I've read in a while. :) – Shimon Rura Feb 26 at 19:24

The issue I have is that the 14-50P has 4 terminals (2 hot, 1 neutral and 1 ground),

Right

but there are only three 10 gauge wires coming out of my brew system (1 hot, 1 neutral and 1 ground).

I think you are mostly likely mistaken on what the wires are.

The terminals in my 14-50P are removable, so should I connect the 1 hot, ground and neutral and remove the unused hot terminal?

You say the brew system is 240V but in the north america (I assume you are in north america due to the mention of a NEMA plug type) you only have 120V between one hot and neutral. If you want 240V you need to connect to both hots (and not the neutral).

You probablly need to connect black and white to the two hot pins (marking the white wire with red tape/sleeving to indicate that it is in fact a hot), green to the ground pin and leave the neutral pin disconnected but check the documentation for the device or ask the manufacturer to be sure.

You should also check what if anything the manual says about overcurrent protection.

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Thanks for the help! The manufacturer says it's fine to plug into the 50amp circuit and the over current protection isn't necessary. I now understand that I need to wire white and black to hot, green to ground and ignore the neutral. Thanks again! – meis1212 Feb 26 at 22:41

It is not ok to directly attach a device that requires a 30 amp breaker to a 50 amp outlet. You need a 30 amp fuse hooked up with 50 amp wiring between your brewer and the outlet.

Just imagine a short circuit in the your homebrew that would normally trip a 30 amp breaker, but in this case you you would need to flow over 50 amps through that 10 gauge wiring before the circuit breaks, likely causing a fire.

EDIT: Now if everything that's wired is within fire resistant enclosures, it would probably be fine without requiring 50 amp wiring or a fuse.

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Thanks for the response. What would be the easiest way to do this? Could I wire up a subpanel that plugs into the 14-50R, has a 30 amp breaker, and is wired to a 6-30R? I want something that can be used when needed, but frees up my 14-50R when needed for my electric vehicle charger. Thanks! – meis1212 Feb 25 at 20:29
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Is it true that the homebrew system requires that overcurrent protection trigger at over 30 amps? I think it's more likely that the system requires the ability to draw up to 30A, in which case using a circuit wired for 50A is totally fine, just like it's fine to plug a lamp that draws 1A into a circuit rated for 15A. – Shimon Rura Feb 25 at 20:45
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Yes, just about everything in your house is plugged in to a circuit that the cord or device is not rated for. i.e. 16 gauge cords plugged in to 15 or 20 amp circuits. This is normal and is not a problem with cord connected equipment. Also with permanent wiring as long as you don't exceed the tap rules of the NEC. The 10 foot tap rule allows conductors to be up to 10 feet long and 1/10 of the ampacity of the upstream overcurrent device. So, you could actually tap a #12 wire to a 2/0 wire without an overcurrent device for up to 10 feet. There is also a 25' rule for ⅓ rated conductors. – ArchonOSX Feb 26 at 1:28
    
@ArchonOSX -- overall true, although the tap rules don't apply to receptacle outlets. – ThreePhaseEel Feb 26 at 4:49
    
@ThreePhaseEel True the tap rules are for feeders. I meandered there. I guess I was just trying to show there are examples of conductors protected at a higher rating if they are of limited length. The code requires power conductors generally to be a minimum of #14 and yet we can buy listed extension cords that are smaller than that and practically every appliance has a cord smaller than that. I am then left wondering what would be wrong (according the NEC) with using a #10 cord for a 30 amp load on a 50 amp circuit. I still can't find that in the code. – ArchonOSX Feb 26 at 9:30

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