I just bought a steam generator for a shower enclosure and have some questions that I am hoping you can help.

It is a 9Kw 240V (1 PH) and The installation manual calls for an 8mm2 wire and it has a peak draw of 37.5A.

1) What is the associated AWG and proper circuit breaker?
2) It is a single phase and as such I guess I should use a wire that has two hots and a ground with no neutral (is this correct).
3) Having said that this unit said it should be installed with a GFCI , but I am confused since there is no "neutral". How is this accomplished without a "neutral". By the way competitive brands recommended that no GFI be installed because of "nuisance" trips.

Thx for your help

1. 8 square millimeters is slightly smaller than 8AWG. Use 8AWG

2. Yes, use 8/2 with ground romex. At all splices and terminations wrap black tape around the white wire to identify it as hot.

3. The 2 pole GFCI breaker will work in much the same way as a single pole GFCI but instead of comparing current between hot and neutral it checks between the two hot conductors. Current on either one of the hots must return through the other hot or it trips. Always follow manufacturer instructions.

Thank You . Tev

If I use 8 AWG I should use a 40AMP breaker. Is that small for an appliance that uses 37.5A? It is dedicated and will only run for 1/2 hour at any given time?

Should I use a GFI breaker at all since some manufacturer say no because of "nuissance". Not sure what that means?

As Tev stated, I would check the installation manual, it will usually state what the minimum size circuit breaker and ampacity circuit should be installed with the generator. I would think it would require a neutral due to your controls. The controls are usually 120VAC and would need the nuetral to produce this. Unless it is just an on off switch, but I would assume that it has an internal contactor with a 120VAC coil.

pcampion, no disrespect but are you a licensed electrician? I believe Tev was referencing the GFI instruction.

The appliance did not give a circuit breake size it just gave the amps that it draws and the wire size which needs to be used. The rest is really up to code in different areas.

Most 240V appliances do not have a neutral. The reason I am confused at this time is that the appliance is calling for a GFCI breaker and I have never installed that on a 240 without a neutral. The GFCI breaker has a clamp down for two hots and a neutral and then a pigtail that goes to the "neutral bus" If I use an 8/2 or 6/2 do I plug the two hots intpo the GFCI breaker and leave the neutral empty an connect the pigtail?

The other question about the 40AMP was that most place like to have the total load of the circuit not exceed 80% of the circuit breaker. Since the generator is 37.5AMP this would nake it close to 45AMP do I then jump to a 50AMP circuit breaker with 6/2 wire (which I don't really want to do since I bought the 8AWG) or is the 80% rule really not a concern here since the generator will be the only load on this circuit.

Thx

I am not licensed in electrical, but I am for mechanical. I have been in the mechanical, electrical and plumbing industry for a long time. If you can let me know what make and model of unit, I will research it and let you know. I am agreeing with you on the 40A circuit, that may be too small for 37.5A, the mfg is probably going to require a 50A, just a guess. This would be in the installation manual, which is probably on line. You could try the 40A circit, but it may trip from time to time. I also checked a few wiring examples on line, and found that there are instances of 3 and 4 wire installations for GFI's. For the 3-wire (in your case) no neutral is run from the CB panel to the device, but the pigtails are hooked to the neutral bus. Hope this may have helped.

Yes, you should use a GFCI because that is what the manufacturer calls for.

As for breaker size, use a 40A. You don't need to worry about the 80% for this application.

Mind if I ask what brand you bought?

GSICI, are you in the US. If not then none of our NEC, or other, rules or wire sizes would apply.

This would be a good thing to know from the start.