Sizing Oven Circuit

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curt swartz

Electrical Contractor - San Jose, CA
Location
San Jose, CA
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Electrical Contractor
I just looked up the circuit size required for a new Bosch oven. This unit has a single oven on the bottom and a microwave on the top. The spec sheet says the total wattage is 10.2 KW and requires a 50 amp circuit.

Here are the detailed specs:

Bake Element Wattages cavity 1 (W): 0 kW
Broil Element Wattages cavity 1 (W): 0 W
Convection Element Wattages cavity 1 (W): 0 kW
Microwave Wattages (W): 1,200 W
Bake Element Wattages cavity 2 (W): 2,000 kW
Broil Element Wattages cavity 2 (W): 3,600 W
Convection Element Wattages cavity 2 (W): 2,000 kW

As far as I know you can only have 1 element on at a time in the lower oven. The largest of the 3 is 3,600 watts. The microwave is shown at 1200 watt which is probably the output of the magnetron so the input is slightly higher. How do they come up with 10.2 KW? Even if all elements were on at the same time including the microwave the load would not be that high but I don't think that is even possible. It just seem crazy to run a 50 amp circuit to when the load when the maximum load is probably around 5KW.


Without having the appliance onsite to verify the nameplate I guess we are stuck running the 50.
 

Dennis Alwon

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The bottom oven will have both elements on during preheat, as far as I know. I also don't know why T.330.55 can't be used.
 

infinity

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New Jersey
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Maybe the 2 millions watts has something to do with it? ;) Just kidding, there's a typo in your list. Bottom line is that you required to run a 50 amp circuit to this thing.
 

curt swartz

Electrical Contractor - San Jose, CA
Location
San Jose, CA
Occupation
Electrical Contractor
I just looked at the specs for a Bosch double oven. They list the exact same 3 wattages for both ovens but the total wattage for the appliance is 8KW. If that is the case the wattage for this unit should be 4KW plus the microwave. It could easily run off a 30 amp circuit.
 

Dennis Alwon

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Dennis, look at note 4 under the table. I think we have to consider this 1 wall mounted oven so the nameplate must be used.

Not sure since none of these apply to the OP. I think Note 3 applies.

4. Branch-Circuit Load. It shall be permissible to calculate the branch-circuit load for one range in accordance with Table 220.55. The branch-circuit load for one wall-mounted oven or one counter-mounted cooking unit shall be the nameplate rating of the appliance. The branch-circuit load for a counter-mounted cooking unit and not more than two wall-mounted ovens, all supplied from a single branch circuit and located in the same room, shall be calculated by adding the nameplate rating of the individual appliances and treating this total as equivalent to one range.
 
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curt swartz

Electrical Contractor - San Jose, CA
Location
San Jose, CA
Occupation
Electrical Contractor
I'm not sure how Note 3 would apply since the rating of the appliance is 10.2KW. Note 4 requires the nameplate rating to be used for sizing the branch circuit for a single oven.
 

curt swartz

Electrical Contractor - San Jose, CA
Location
San Jose, CA
Occupation
Electrical Contractor
Is it a single Oven???? YOu are probably correct but there are 2 ovens.
It is a single oven with attached microwave. Can we consider that 2 ovens and use the demand factors? Its hard to tell.

The funny part is if you run a feeder to a small panel at the oven you can apply the demand factor to the feeder even if there are not other loads.
 
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