GFI for 480volt Circuit

[Kicker_92]

I have a tank heater (parts hot tank) which runs off 480VAC/1ph, and would like to have a GFI for it just in case theres a short. Water and high voltage is not a good mix! The control for the heater is 120VAC.

From what I've been able to source locally, a GFI for this voltage is special order, and would be $5-6000. Anyone know of a good source for stuff like this?

I'm thinking instead, maybee putting a big relay on the main circuit, using a transformer to step down the 480 to 120 for the control circuit, and putting a standard GFI on the control circuit. My thought is that if anything shorts, the control circuit GFI will trip, and could cut the power to the main relay. Would this work?

Basicly my question is: If you have a GFI on one part of the circuit, will it trip if another part of the circuit shorts out? Electrical new to me, I've tried searching around on the web and couldn't find any good info. Just want to make this hot tank setup safe...

[u2slow]

I just Googled up this one:

http://www.lindequipment.net/hd-pro.htm

I'm curious about your 480V 1Ø setup... Do you have 480V 3Ø in the building, and you're just using two 'hots'?

Is the system grounded? Or does it have 3 lights somewhere for fault detection? You will have a hard time with ground fault protection on an ungrounded-delta system.

I dunno what liquid you're heating up in this tank, but consider the possibility of corrosive vapours and proximity of the enclosures and equipment you're choosing for your control circuit. You could use a seprate 120V GFCI protected circuit with a contactor to turn the heater on & off.

A non-metallic control box with plastic buttons might offer some peace of mind also.

[tippy99888]

Are you sure you even have 480 volts where your at? I was under the impression that 480V was an american voltage and we (canadians) used 575V. You can use a CT (control Xmfr) then a cheap way to do it would be to run it through a GFCI receptacle. Run the power from the xmfr through the line side of the rec. then out the load side. This set up will not protect the heating elements though, only the control part of the circuit. The reason that the 480V GFCI breaker is so expensive is because most of the people using anything with that kind of voltage is in an industry application. The company's know that they will pay the bucks for it cause they can get it back in taxes somewhere.
Just a thought, but it might be cheaper to use a 240 volt breaker and step the voltage up to 480 with a 1:2 xmfr. The GFCI is a good idea, but I'm not sure it will work for the heaters cause it would have to go through the XMFR. If you install it properly with a regular breaker, and have a good ground connection it should trip if there's a problem. Voltage will take the easiest path to ground, and that should be through the liquid to the frame of the washer then trip the breaker.

[Kicker_92]

I like the idea of the non-metal control box and buttons.

Our shop has 575, 460, and 240 three phase. It's a small company, so people have to cover a lot of differant jobs, hence me setting up this heater system. Unfortunatly this also mean we have a limited budget for this.

Basicly it's a parts cleaner tank with a NaOH solutions which will be at 160*F. The heater is from Chromalox, http://www.chromalox.com/products/prodinfo/en/pthptht.html
and are 3kW, 480V, single phase.

I was assuming that from a 460 outlet, I could use two of the power leads and a ground. Like I said before, three phase is something new to me, so any help is appreciated. My concern is that over time with parts going in and out of the tank, the heater sheath might get damaged and short out through the tank to a person who touches it.

Does anyone know of a wiring diagram for a similar application? Someone mentioned that some Hot Tubs have a ground fault in them and might be similar, but I haven't been able to find any scematics for the internal wiring of them.

Thanks,

[u2slow]

There is still lots of 480V around because its such a common machine voltage. Many places have a 600V or multi-kV service and step it down for their machines.

Sometimes run into 240V 3Ø-delta in older light-industrial areas.

347/600V and 120/208V are the most common though.

Kicker, a 480V system should really be left up to an electrician. Residential services top out at 120/240V for a reason. Moreover, it you lease/rent this facility, you would be in a bad situation for liability if something happened - if your agreement even allows DIY electrical improvements. :(

PM me if you want to take this further :)