3 Wire vs. 4 Wire connection - 240 V.

[Bad Bubba]

I am converting over to electric brewing and I had an electrician run a 240V - 40 AMP circuit to my brew room. He installed a 3 prong receptical (3 wire) but said he could come back and make it a 4 wire if need - the wires are there. As I started to research controllers I see there are some that use 3 wire and some 4 wire outlets. Here is my question, should I have the electrician come back and rewire my outlet with a 4 wire unit? My understanding is that I can get an adapter so I could plug in a 3 wire controller if I would need to - is this true? I just am thinking it will give me better long term flexibility. Any thing else I should be considering?

 

[doug293cz]

Yes, a four wire outlet will give you more flexibility. You can get a 4-wire to 3-wire converter, but you can't go the other way.

Brew on

 

[Bad Bubba]

Thanks. That is what I thought but wanted to get confirmation from someone who knows this stuff better than me - and that is you for sure!

 

[InspectorJon]

3 wire for 100% 240 volt applications is all you need. 4 wire is preferred if your system has any 120 volt application. If you run any 120 volt processes with a 3 wire supply you risk putting current potential on the equipment grounding system.

 

[BrunDog]

Also check that the wiring is run back and wired to a proper GFCI breaker. The neutral would need to be wired to that breaker.

 

[doug293cz]

Also check that the wiring is run back and wired to a proper GFCI breaker. The neutral would need to be wired to that breaker.

Lack of neutral connection to the GFCI breaker would reveal itself as soon as a 120V load was connected to that circuit. The GFCI would trip since the currents would not be equal and opposite on the two hot lines.

Brew on

 

[BrunDog]

Yes but 120V wouldn’t even be possible without the neutral unless the ground was the return path.

 

[doug293cz]

Yes but 120V wouldn’t even be possible without the neutral unless the ground was the return path.

I was talking about the case where a neutral was present, but not connected to the GFCI breaker correctly.

Brew on

 

[Bobby_M]

The bottom line is that you should pick a controller first. If you go for the Blichmann Brew Commander, it uses a 3-wire 240v and a separate 120v circuit for the pump switch. Other controllers like the Auber cube use a 4-wire 240/120v plug standard so that it can power the pump output circuit without a separate 120v input.

Another way to approach it is if you have it wired with 4 wires, it will support ANY controller. If the controller doesn't need the extra wire (neutral), you'd just not use it.