Double oven on 30 amp circuit (Table 220.55)
- Thread starter crtemp
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- Tennessee NEC:2017
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- Semi-Retired Electrician
Table 220.55 is for demand factors and loads, that is for service load calculations. For branch circuit load you need to look at note 4 of the table.
Does the nameplate cover both ovens, or does each oven have a nameplate?
I believe it is for both ovens. I guess I'm screwed then since it comes out to 30.8 amps
curt swartz
Electrical Contractor - San Jose, CA
- Location
- San Jose, CA
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- Electrical Contractor
Table 220.55 can be used for branch circuit load calculations but you need to see Note 4.
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.
Since you have a single (double) oven you need to use the nameplate rating.
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.
Since you have a single (double) oven you need to use the nameplate rating.
It sounds like you are trying to size the conductor and overcurrent protection for the oven. I would look at section 210.19(A)(3) for guidance. It states:
Household Ranges and Cooking Appliances. Branch circuit conductors supplying household ranges, wall-mounted ovens, counter-mounted cooking units, and other household cooking appliances shall have an ampacity not less than the rating of the branch circuit and not less than the maximum load to be served. For ranges of 8.75kW or more rating, the minimum branch-circuit rating shall be 40 amperes.
goldstar
Senior Member
- Location
- New Jersey
- Occupation
- Electrical Contractor
Any double wall ovens that I've installed all have required a 40 amp circuit. This is not a scientific analysis but if the unit is on the job take a look at the whip coming off the back. If it has # 8's you'll need an 8/3 cable
- Location
- Chapel Hill, NC
- Occupation
- Retired Electrical Contractor
I disagree that the table is for service calculations only. If so you would not be able to use the Notes and the Notes take us back to the Table.
IMO, if you have a double oven then you would do as the op stated. Take the 7.4kw and use column B. So 7400 * .8= 5920 watts. Divide by 240 and you have 25 amps. I believe the 10/3 would work but I am not sure I would use #10. The ovens have t-stats so the loads generally won't be on at the same time for long periods. Even if they are the load is just over 30 amps with no demand and that is not likely to trip the breaker.
I guess it depends if you see this as one oven or two ovens. If it is one oven then I guess a 40 amp circuit is needed.
- Location
- Chapel Hill, NC
- Occupation
- Retired Electrical Contractor
Remember a 9kw thru 16kw range can be installed on a 40 amp circuit.
Dennis, what about Note 4 to 220.55. Would that not direct us for one wall mounted oven, the branch circuit shall be the nameplate rating ?
- Location
- Chapel Hill, NC
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- Retired Electrical Contractor
Yes but is this one oven or two single ovens? The thing I don't get is there is no direction for 2 ovens.. I believe I should eat crow on this one as the ovens are probably considered one. I did mention that at the end of my post.
- Location
- Chapel Hill, NC
- Occupation
- Retired Electrical Contractor
If there were a range with 1 or 2 wall ovens we could then treat it as one unit and then use the table. But since this is just an oven I think we are stuck with using the nameplate. I guess the range adds the diversity and an oven does not have the different temperatures -- it is either on high or off
- Location
- Tennessee NEC:2017
- Occupation
- Semi-Retired Electrician
I suppose I could have worded it different but I did say to look at note 4.
IMO, the columns A, B, & C are for load calculations. Otherwise note 4 wouldn't specifically say for "branch circuits". You don't usually have demand factors for branch circuits. They are for the total load.
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