3 phase heating elements

[Bigrhamr]

I've got a chance to buy, dirt cheap, 2 ovens that were used as varnishing ovens. They are supposed to heat to 600 degrees. The question I have is about the electrical system. They are 3 phase and wired for 460 volts, I have 208 3 phase in my shop and can reconnect them to run at the lower voltage. What I don't know for sure is how much the lower voltage will affect the output of the elements. Would wiring the elements in series vs. in paralell have something to do with it? Any electrical guru's here that can help with that?

Thanks in advance.

[ed_denu]

An element rated at a specific voltage will output considerably less wattage if input with a significantly lesser voltage. In this case going from 480 to 208 would reduce the output wattage about 80%.

The ovens may still be a good deal if you want to take the time to configure them to operate acceptably on a lower voltage. The first picture you attached has what appears to be a wiring schematic that allows for 240 volts? It may be possible to configure this oven to operate on a single phase 240 volt service. It may also work on the 208 three phase you reference. Many 3 phase ovens do not actually use 3 phase elements, but use phase to phase(2 connection) elements and balance the load over 3 elements.

It may be worthwhile to have a qualified electrician review the wiring and give you an opinion on the electrical options. Another option, given the complexity of the wiring, which I would consider, would be to gut the existing electronics and replace with a pid, ssr/contactor and elements rated at the desired voltage. Len (FigureLLC) has a nice wiring diagram for a 3 phase oven setup. You might do a search for it, or perhaps he can re-post it.

[Bigrhamr]

Thank You,
I've been reading that post and all the others I can find. It's now looking like the way to go in this case would be to install a step up transformer and feed it 460v. If I drag them home I'll be back here looking for more advice. One is about 5'x12'x6' tall on the inside and the other is 4'-6" square by 6'tall. The elements are on both sides near the bottom and on the ceiling, they are behind a baffled or louvered cover. Both are built with a track in the floor that would sit at ground level to roll racks in. Walls and doors are about 4" thick and insulated with a dense grey material. They have big exhaust fans with them, 1-1/2 HP motors with squirrel cage type blowers. I assume that was for fumes from the varnish but don't guess I need anything like that for powder?
They've been out of service for 2 years and no info available on what works and what doesn't so it's kind of a crapshoot there,but it seems like even if all the heating equipment needs replaced it would be a good way to start.

Thanks again for the info,
Chris.

[CarWiz]

If they're "dirt cheap", the enclosures alone are worth it. That's the biggest expense of a large oven. I'd say go for it. Even if you have to replace elements it could be a bargain. I've had my eye on a couple of large ovens at the salvage yard but they're stainless steel. They're mighty proud of there SS scrap.

[philipd]

Bigrhamr,

The photo on the left (in your original post) is a close up of a transformer. It is set up to convert 480 3-phase into 120 single phase. It can be configured to convert from 240 3-phase into 120 single phase. Usually this device is used to provide control power to a system. For example a motor starter will use 120 V to energize the coil and when the contacts close 480 V is passed to the motor.