power for an oven

[mx842]

I built a powder coat oven several years ago and never could use it but I'm about finished with my new building and I want to hook it up. It has 3) 208 volt 10000 watt heating elements in it. I was going to use 3 phase current when I built it and is why I used those elements. When I finished the build I put a 50 amp 4 wire plug on it just to see if everything worked ok. It got up to 350 degrees in about 20 min and the fan and lights worked. Since then it has been sitting in storage but now I want to hook it up and use it.

My question is what size wire and breaker do I want to use? When I started it up to test it, it seemed to work okay and nothing got hot but I only ran it about an hour then shut it down. This was with all three burners running and with the lights and fan working. I'm not saying this is right just that on the test run it preformed ok. I had a 100 watt entrance service box on the side that fed my controls. The box was fed by a 50 amp cable plugged into a 4 wire 50 amp plug on the wall.

 

[joefromga]

It was probably only using 2 legs. 10kw isn't that much for a 50amp plug with #6 wire.

 

[mx842]

It has 3 10000 watt burners plus the fan and light circuits.

 

[joefromga]

These are heating elements? 10kw x 3 is 30kw. That's pushing it for 50a plug. You probably need to go the next size or two larger.

Check wire amperage ratings . you're definitely going to be in the direct wire range and won't need a plug at that load. If you go 3 phase it changes things a bit because the 208v is going to pull a few more amps than the 240v you tested with as well as the third leg. You should probably be using at least 4ga wire, copper.

 

[ddbackhoe]

I built a powder coat oven several years ago and never could use it but I'm about finished with my new building and I want to hook it up. It has 3) 208 volt 10000 watt heating elements in it. I was going to use 3 phase current when I built it and is why I used those elements. When I finished the build I put a 50 amp 4 wire plug on it just to see if everything worked ok. It got up to 350 degrees in about 20 min and the fan and lights worked. Since then it has been sitting in storage but now I want to hook it up and use it.

My question is what size wire and breaker do I want to use? When I started it up to test it, it seemed to work okay and nothing got hot but I only ran it about an hour then shut it down. This was with all three burners running and with the lights and fan working. I'm not saying this is right just that on the test run it preformed ok. I had a 100 watt entrance service box on the side that fed my controls. The box was fed by a 50 amp cable plugged into a 4 wire 50 amp plug on the wall.

line to neutral would require 28A per leg, for each heater. Cable length would have to be known for sizing.

 

[jenkinsph]

line to neutral would require 28A per leg, for each heater. Cable length would have to be known for sizing.

Can you explain how you came up with 28A/leg?

P/IxE yields 48A @208v

 

[jenkinsph]

It has 3 10000 watt burners plus the fan and light circuits.

Is your new shop set up three phase? If so I would hardwire the oven with a 60 or 70 amp three phase breaker and use #4 thhn wire for the run to the panel. The load should be about 48 amps for each leg running but these elements do pull more current for a short duration while heating up. So while a 50 amp breaker may work moving up to the 60 or 70 amp breaker might eliminate tripping the breaker or over heating it.

 

[CobyRupert]

I built a powder coat oven ..... It has (3)- 208 volt 10000 watt heating elements in it.

My question is what size wire and breaker do I want to use?

I had a 100 watt entrance service box on the side that fed my controls. The box was fed by a 50 amp cable plugged into a 4 wire 50 amp plug on the wall.

You have 30,000 Watts (or 30kW) of load.
The question we need to ask is how are these elements connected?
Are they in a "delta" formation (where element 1 is connected between phases A & B, element 2 is between B & C, and 3 is between A&C?
I assume so, that is, your not using the 4th wire as a neutral and have the elements in a "Y" (wye) formation where element 1 is between phase A & N, element 2 is between phase B & N, and 3 is between C & N.

If elements are wired in "delta" (phase-to-phase), then the current (I) draw is I= 30,000 Watts /(Sqrt(3) x 208V) =83 amps.
You should size the wire and breaker to handle 125% of 83 amps (104A), So basically #2 Awg and a 125A breaker. .

 

[mx842]

You have 30,000 Watts (or 30kW) of load.
The question we need to ask is how are these elements connected?
Are they in a "delta" formation (where element 1 is connected between phases A & B, element 2 is between B & C, and 3 is between A&C?
I assume so, that is, your not using the 4th wire as a neutral and have the elements in a "Y" (wye) formation where element 1 is between phase A & N, element 2 is between phase B & N, and 3 is between C & N.

If elements are wired in "delta" (phase-to-phase), then the current (I) draw is I= 30,000 Watts /(Sqrt(3) x 208V) =83 amps.
You should size the wire and breaker to handle 125% of 83 amps (104A), So basically #2 Awg and a 125A breaker. .

My shop I built isn't 3 phase.

The shop I built the oven in was 3 phase and I originally wired it up for that. I had to move out of that shop and at that point it went into storage. When I tested it There was a 50 amp plug already on the wall where someone had a paint booth plugged in to it. After checking it out I found out they had the plug wired for single phase not 3 phase. I just changed the wiring in my control box for the test just to see if everything worked.

They hooked it up this way so they could say it was portable and not have to have a $60,000 fire suppression system installed on the booth. That was my thinking as well.

This big oven won't get much use, it's only for when I need to do something really big or if I have a bunch of wheels to do. My smaller oven gets most of the use, it's 24'x42''x4' high and most of the stuff i will get will fit in that oven. It also has one of these 3 tube 10000 watt burners in it so running this one off that 50 amp plug wont be a problem. That circuit is a 4 wire circuit with 6 ga wire that is only about 42' from the box with a 50 amp breaker.

I guess I won't be using this circuit for the big oven after all. I'm thinking now that I'll run another circuit maybe three (one for each burner) so I can keep it portable. I have just enough room in my box for three more 50 amp circuits and I think I have enough wire on hand. Do you think that would work?

 

[CobyRupert]

Now I'm even more confused on what you have.

(1)- 10,000 Watt burner (3 tube) or (3) - 10,000 Watt burners? That is, 10,000 or 30,000 Watts of load?
By burners, I think you mean elements?
If 3 elements, do all 3 come after the re-wire? Sounds like only 1 does, so your load is 10,000 watts?

Even then, it really wouldn't be 10,000W, I mean:
Are you running these (208V) elements on 240V single phase? (i.e. people rarely have 208V single phase and not 208V 3 phase). That is a 10,000 watt/208V element will output a lot more wattage if run at 240V, and a lot less if wired line-to neutral (120V). Current draw is also dramatically effected.

Are the element(s) wired line-to-line, or line to neutral?