# 3-phase vs single-phase heating elements

• posted on August 18, 2007, 8:30 pm
Figured you guys would know...
I have found a used 220 v 3-phase oven that I would like to use in my shop. The problem is that I only have 220v single phase. Without going to a phase converter is there a way I can run the oven off of
single-phase by re-wiring the heating elements? IOW...how would I reconnect to single phase to not overload the elements but also give me the heat I need?
(Oh, even though I'm fairly electrical-challenged I did some homework and learned that there are two basic ways 3-phase elements are wired, star and delta. I just don't have enough knowledge of AC circuits to figure out how to swap the elements or if it's even feasible.)
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• posted on August 18, 2007, 9:36 pm
I rewired an infrared 220 3 phase heater. it had three elements. one between L1-L2, one between L2-L3, and one between L1-L3, Yours is likely the same.
I ran three single phase 220 circuits, one to each element, worked fine.
Karl
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<%-name%>
• posted on August 18, 2007, 10:02 pm
wrote:

Good info. I did some more homework and it looks like I could do this but my amperage would go up 1.73X (sqrt 3) as much.
How about this idea- after I rewire to single phase can I run three breakers, one for each element, and then turn each on one at a time so that I don't spike my power? I have 200 amp service to my shop and each breaker would be 50 amps. The unit as 3-phase is 30KW at 220V for a 3-phase amperage of about 79 amps. With single phase I would be looking at about 137 amps, hence the three 50 amp breakers. How practical is this in a home shop?
The other question... each element sees the same voltage but what about the same power and will it kill my elements?
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• posted on August 18, 2007, 10:24 pm
It all depends on how they are wired. It may or may not be easy to rewire. Open the case and look. Even if they are delt wound (forming a triangle), you may get 2/3 of power from them.
i
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• posted on August 18, 2007, 10:29 pm
I'll defer to the electrical gurus that will chime in...
start with the basics. measure the resistance of a single element. Divide into 220 to get amps. V=I*R V/R=I. That's a big heater, you may want to run only two elements.
Karl
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<%-name%>
• posted on August 19, 2007, 10:21 pm
On Aug 18, 6:02 pm, snipped-for-privacy@yahoo.com wrote:

Careful here. Make sure it's not 'center tapped` , Wye connected Thats 120V. per coil. If so 240V. will fry it. But it can be wired for separate 120V. Lines. If the coils are wired delta, phase to phase then, If it's 3 Phase, and t's sized at 208V. Design is : 10 KW. , 40 A. / Coil What you are supplying is 240V., so you'll get : 11.5 KW. , 46A. / Coil.
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• posted on August 19, 2007, 12:21 am
snipped-for-privacy@yahoo.com wrote:

The first thing to do is determine if the elements are wired in Delta or Wye (Star). Either way it will not be too hard to convert. You also need to find out what control is on the oven. It the elements are in a Delta setup you will have to rewire the elements so each element is in parallel with the other. If the elements are in a Wye configuration you will need a neutral wire to attach to the centertap of the Wye and tie two of the high legs together and feed 220 across the single high leg and the other set of two legs that are tied together. You could put separate circuit breakers on each leg. One thing is that the neutral conductor has to carry the current of two elements as should be sized accordingly. Do not put a breaker or disconnect switch in the neutral wire circuit.
None of the above will work with proprotional control circuits, semiductor switching power control.
John
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<%-name%>
• posted on August 19, 2007, 12:52 am
On Aug 18, 1:30?pm, snipped-for-privacy@yahoo.com wrote:

First of all determine if the heater elements are 220v or 110 volts. If they are 220 your unit is probably wired delta. If 110 volts then WYE. They are marked somewhere. Also determine the KW rating of each heater element.
Remove all the wiring.
If the elements are 220 then wire each individually to a 2 pole 220 volt breaker. No neutral needed.
If 110 volts then wire each individually to a single pole 110 volt breaker. A neutral will be needed.
As another said watch out for the neutrals. If you end up wiring for 110 volts make sure you wire them to alternate hotlegs of the 220 single phase in your panel. Don't make the neutral wiring smaller than any 110 volt wiring.
Also any wiring within the heater must be, HPN I believe it the word, IOW high temperature rated. And the terminals on the heaters also heat rated. (I am not up on the wire and terminal types.)
I am guessing here but I would imagine that this heater is too much for the 220 single phase service you have to your shop. An upgrade might be in order.
Bob AZ
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• posted on August 19, 2007, 3:21 am

Yes, I agree. It is important to determine if the elements are for 220V or 110V (3 phase makes it 08V live to live), it makes a big difference. From a different angle, 137 A power draw may be a little high for a typical home. You may need to make sure your main breaker can take it.
Ken
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• posted on August 19, 2007, 6:25 pm
Torrey Hills wrote:

YOur household electric stove and oven doing a Thanksgiving dinner takes more than a small heat treat oven. Its not a car bottom heat treat oven I hope. My 12 x 12 x 20 inch 2000 degree F oven is less than 5000 watts. That is only roughly 25 amps at 220 volts.
John
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• posted on August 20, 2007, 6:46 pm
snipped-for-privacy@yahoo.com wrote:

Star and delta is a start. Where I used to work we ran die heaters on 460v so you ended up with some heaters in series and in then in delta.
You need to diagram your current wiring configuration. Depending on how many variations to deal with differing voltage supplies at customers they (manufacturer) may have used there could be something strange in there.
Considering the 137A I doubt any allowances to rewire for 120v was in the design so I bet each element segment is 220v
My bet is that it is delta but it is only a hunch.
E=IR P=IE Resistance tends to increase with temperature in most materials.
BTW, what is the internal size of this thing? How hot does it get? What kind of control?
Wes