GFCI for a mixed 120 / 240 box

Ok, there a lot of threads on this topic with a lot of posts in each. I'm looking for a concise answer on this instead of wading through hundreds of pages about why it's scary that someone's electrician said that a GFCI wouldn't work on a 240V circuit that doesn't have a neutral line.

I want to have one power supply to my brewing control box. I have a 50A "welder" outlet and circuit in my garage that I'm planning to tie into, but I would also like my brewing rig to be portable. Theoretically, I would really like to have a breaker box with a GFCI installed on my rig that could act as a cutoff and lockout for the entire system.

I plan on running two pumps, a stir motor or two and a 4500W heating element using SSRs. What is the clean way to protect this circuit?

The typical 240V spa GFCI option that monitors the two load lines won't work if I turn something on that only uses 120V. Similarly, monitoring each load with respect to the neutral line won't work because my 240 heating element isn't sinking current to the neutral line.

Is there a third option? Or should I just replace my 240 breaker with a GFCI breaker and constrain myself to that one outlet?

I know that there should be a straightforward answer to this because I know that plenty people out there are running mixed voltage electronics boxes. Any thoughts?

Im going to reply to see what is said about this. Good question!

The spa panel will work. GFCI measures what goes out and what comes back and compares them, it doesnt mind off balance loads. I use it in my setup and it works beautifully.

Joshua

Disclaimer - I don't know anything with you crazy American 120/240V system!
Would you not have a main 240 GFCI that the feeds 2 x 120 GFCIs?

So are you saying that the GFCI circuit breaker used in a spa panel is the type that measures all three paths that the electricity can take (L1, L2 and N) and makes sure that there's no current flowing elsewhere? I assume that also mean that the wiring run to a spa breaker panel has to be a 4-conductor cable (L1, L2, N and G). Similarly, you need to run a 4-conductor supply from the spa panel to your electronics box. Is that correct?

mattd2 said:

Disclaimer - I don't know anything with you crazy American 120/240V system!
Would you not have a main 240 GFCI that the feeds 2 x 120 GFCIs?

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All of the GFCI circuits that I've ever dealt with have essentially had two leads. One is connected to the load line and one is connected to neutral. If the current flowing out on the load line doesn't match the current flowing back in on the neutral line, then there's a short to ground somewhere (there are actually other possible faults but that's another discussion). That trips the GFCI. With a 240 circuit here in the states, you don't actually have a neutral line. The 240 is actually two 120 lines that are 180 deg out of phase, giving the 240V. That still works for the normal style of GFCI since there are only two wires involved in the circuit, L1 and L2. If the current out on L1 doesn't match the current coming back on L2, then there's a short somewhere.

Well, since I want my electronics box to run some things at 120 and some at 240, I will have current flowing on L1, L2 and N at any point in time. If I had 2 120 GFCIs then whenever I turned my heating element on I would have current flowing out on L1 and in on L2 with no current flowing on N. That would trip both GFCIs. Instead if I had a normal 240 GFCI, it would monitor L1 and L2, but if I turned on something that used 120 there would be current flowing on L1 and N but not on L2. That would also trip the GFCI.

I've heard rumor of circuit breakers that monitor all three lines. Essentially they would make sure that the net current flow on the three lines is zero. I'd like for someone to confirm their existence and to tell me whether or not that's the typical hardware found in a spa breaker box.

The safest way for a dual voltage box is to have two inputs. You never want 120 running on 240

there are 3 wire (no neutral) and 4 wire spa panels. the link below should really help, especially the wiring diagram:

http://www.spadepot.com/spacyclopedia/wiring-hot-tub-spa.htm

i'm not sure what steelebrew is trying to say. i've got a 4 wire 240V GFI feed into my control box that feeds both 240 and 120 volts to various pieces of equipment, which is entirely acceptable.

p.d.

bblack7489 said:

So are you saying that the GFCI circuit breaker used in a spa panel is the type that measures all three paths that the electricity can take (L1, L2 and N) and makes sure that there's no current flowing elsewhere? I assume that also mean that the wiring run to a spa breaker panel has to be a 4-conductor cable (L1, L2, N and G). Similarly, you need to run a 4-conductor supply from the spa panel to your electronics box. Is that correct?

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In order to have a 240V GFCI circuit that feeds 240 and 120 safely, you must have 4 wires going to the panel and 4 going to the brewery from it. It might cost you a little more, but it is completely worth it.

There are a number of threads on this if you have a look around.

Joshua

jfkriege said:

In order to have a 240V GFCI circuit that feeds 240 and 120 safely, you must have 4 wires going to the panel and 4 going to the brewery from it. It might cost you a little more, but it is completely worth it.

There are a number of threads on this if you have a look around.

Joshua

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That's a heck of an understatement. There are a ton of threads with a lot of varying information. However, the link that paledragon posted above is great and answers the question concisely. The short answer is that a 4-wire spa panel will allow you to run a mixed voltage system on a single circuit.

"Hot tubs with mixed voltage components (such as 120V ozonator and 240V heater) require 4-wire systems, which means they require an electrical circuit providing (2) hot wires, (1) neutral, and (1) ground wire."

That's exactly what I wanted to know.