# How to power a 120/240 volt 3 phase oven in a building with 120/240 volt single phase



## Yoyizit (Jul 11, 2008)

If there are no motors in the oven you might get by with paralleling each terminal for each phase but I'd first post a schematic. 
It's likely pasted on the inside of some panel in the oven.
With 15 kw you'll need [email protected]


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## Speedy Petey (Feb 1, 2004)

Your electrician should have no problem working this out.

If you have to come to a DIY message board to ask: _"Exactly what am I going to need to power this oven?"_, then you really have no place trying to wire this thing in a commercial setting.


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## wantsomegetsome (May 3, 2009)

Speedy Petey said:


> Your electrician should have no problem working this out.
> 
> If you have to come to a DIY message board to ask: _"Exactly what am I going to need to power this oven?"_, then you really have no place trying to wire this thing in a commercial setting.


It's in my house. 

I want to do it myself because I have little money.

I need to know how do I power a 120/240 volt 3 PHASE oven in a building with 120/240 volt SINGLE PHASE utility.

Do I need a single phase to 3 phase converter, transformer, variable-frequency drives, etc?

The parallel thing seems the cheapest if it is possible. There are no motors for the upper part of the oven which is 3 phase and only consists of the burners. The schematic is gone. I can see the glue outline of where it used to be. I have sent an e-mail to the manufacture to see how I can get a new one.

Only 1/2 of the upper oven will be in use for about 2 hours in a day, 2 or 3 times a month with me standing right in front of it the entire time. Power will be shut off at the circuit breaker when done. Might not use the 3 phase upper part (baking) if it is going to be too much money to get it to work. I could just use the lower single phase proofer part of the oven and my regular oven for the baking.


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## Speedy Petey (Feb 1, 2004)

wantsomegetsome said:


> It's in my house.
> 
> I want to do it myself because I have little money.


Ohhh. You referred to it as _"a building with 120/240 volt single phase"_. I think you can see the reason for my confusion. Folks don't normally refer to their houses as "buildings".


Many 3-phase ovens can be wired for single phase. ALL elements are single phase so it is all a matter of how and how many are wired in parallel.
You will certainly need the manual or a wiring diagram.


The FIRST thing I would do is see if this unit is even approved for use in a dwelling. Most true commercial ovens are NOT.


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## Yoyizit (Jul 11, 2008)

If you don't mind 7kw total maybe you can wire just one of the three phases in the upper oven. It might even be safe, then, for houses.

An old oven may be simple enough that you can draw a wiring diagram by inspection.


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## micromind (Mar 9, 2008)

You'll need to find where the elements are connected to the power wires. Almost certainly, there are 3 or 6 elements, and they are delta connected. You'll need to connect each one in parallel with the others.

The wire will now be too small, and will need to be replaced with larger. It might be somewhat difficult to find wire with a high enough temperature rating. 

The contactor might be too small as well. Since the current was spread out amongst 3 legs, and is now across two, the current will be higher. A contactor that can handle the current will be easy to find. 

If you connect single phase power to L1 and L3, the lower part will work as always, the upper part will work at about 1/2 the normal wattage. The contactor and wiring will be able to handle the current as-is. 

If you don't re-connect the elements, and both upper and lower operate at the same time, you'll need a 70 amp supply. One leg will have about 25 amps, the other about 50. If they don't operate at the same time, a 40 amp supply will do. 

If you do re-connect the elements, and they operate at the same time, the supply will need to be 100 amps. One leg will be about 50 amps, the other about 75. If they don't operate at the same time, 70 amps will do. 

Rob


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## wantsomegetsome (May 3, 2009)

The oven has 8 elements. 2 on the top, 2 for the 1st rack, 2 for the 2nd rack, 2 for the 3rd rack. 

This is a picture of where I see the wires are going. I'm still trying to get a real electrical diagram from the manufacture.


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## wantsomegetsome (May 3, 2009)

Yoyizit said:


> If you don't mind 7kw total maybe you can wire just one of the three phases in the upper oven.





micromind said:


> If you connect single phase power to L1 and L3, the lower part will work as always, the upper part will work at about 1/2 the normal wattage. The contactor and wiring will be able to handle the current as-is.


I like this. I will only be able to use 4 elements and leave the others turned off. It may take longer to preheat, but this seems to be the easiest and cheapest. 






Parallel

This will allow me to use all of the racks. I like this one too but will have a little more work to do and it will be more expensive.

I need to find the temperature rating of the current wires.

Buy more expensive higher amp wire with a temperature rating that matches or is better than the current wires.

Buy a higher amp contactor.

Here is what I understand for the parallel wiring: 










The red wire will need to be 75 amps wire and the black one 50 amp wire.


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## Yoyizit (Jul 11, 2008)

You should measure the resistance of the elements before you buy any parts.

R = (V^2)/P, so for P = 3000w and V = 240, R = ~19 ohms.


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