Cooking equipment less than 8 3/4 kw. Overcurrent protection

[SOwings]

The issue of the correct overcurrent device for single fed cooking appliances had bugged me forever an I have not been able to get a clear answer. I will tell you what I currently do and why and perhaps y'all can approve it or tall me what I am doing wrong. I will be content either way.

I go to article 240 and Table 240.3 sends me to 422. Section 422.10(A) refers me to Table 220.55 and 210.19(A)(3).
Table 229.55 tells me to take 80% of the nameplate for cooking equipment under 8 3/4 kw.
210.19(A)(3) tells me that under 8 3/4 kw they shall have an ampacity not less than the branch circuit and not less than the load to be served. Since the branch circuit is the kw rating at 80% and the load to be served is the actual kw rating, I would assume then that the overcurrent device would be the higher of the two or the kw eating at 100%.

Someone was telling me to use 125% but this seems unreasonable since cooking equipment universally gets the branch circuit derated.

I would appreciate input.

 

[infinity]

Do you have a specific KW rating in mind?

Welcome to the Forum.

 

[david luchini]

Since the branch circuit is the kw rating at 80% and the load to be served is the actual kw rating, I would assume then that the overcurrent device would be the higher of the two or the kw eating at 100%.

I think you have this confused. The load to be served is 80% of the rating of the appliance per T220.55. The branch circuit rating mentioned in 210.19(A)(3) is the size of the branch circuit OCPD.

If you had one cooking appliance rated at 8kW, 240V, then 80% of that is 6.4kW, which is 26.7A @ 240V. That is the load. 210.19 tells you that you need conductors to be at least #10 to carry the load. So you could have #10 on a 30A branch circuit. Or you could have #8 on a 40A branch circuit, etc.

 

[SOwings]

Let's assume we have a 6.4 kw oven. Branch circuit would be 26.66 * .8 = 21,33 or #10 copper. Now would the ocpd be sized 25 amp (80% of load like the branch circuit) or 30 amps based on the actual load? Since you are protecting the oven you could not increase the circuit and the ocpd above this.



I do realize that once you hit 8 3/4 kw you can go with 30 amps all the way to 12 kw.

 

[Dennis Alwon]

Let's assume we have a 6.4 kw oven. Branch circuit would be 26.66 * .8 = 21,33 or #10 copper. Now would the ocpd be sized 25 amp (80% of load like the branch circuit) or 30 amps based on the actual load? Since you are protecting the oven you could not increase the circuit and the ocpd above this.
I do realize that once you hit 8 3/4 kw you can go with 30 amps all the way to 12 kw.

Table 220.55 col. B allows 80% demand factor for one appliance. 6400*.8 / 240= 21 amps. You do not need to do 80% of the breaker as long as a load is not continuous. An oven has a t-stat so the load is not continuous. I would run a #10 wire and install it on a 30 amp breaker. The load served is 21 amps, IMO.

 

[Smart $]

...

I do realize that once you hit 8 3/4 kw you can go with 30 amps all the way to 12 kw.

210.19(A)(3) in part states, "For ranges of 8-3⁄4 kW or more rating, the minimum branch-circuit rating shall be 40 amperes."

 

[CONDUIT]

If this is a branch circuit for a cooktop or oven you had better read note 4 to table 220.55.

 

[SOwings]

Smart $ - I knew that, just hit the wrong key - it's my fat fingers (but thank!), Conduit, I knew about note 4 and combining a cooktop with 1 or 2 ovens, but reading about one oven or cooktop having a branch circuit at their kw rating seems to directly conflict with the table.
Anyhow, thanks to all, I believe y'all have confirmed I was (am) properly interpreting this.

 

[infinity]

Dennis has the answer in post #5. If you want you can use the #10's with a 25 amp OCPD.

 

[curt swartz]

Dennis has the answer in post #5. If you want you can use the #10's with a 25 amp OCPD.

I disagree. As Conduit said above note 4 states the branch circuit load for a single oven or cooktop shall be the nameplate rating of the appliance. If you connect multiple appliances to a single branch circuit then you can use the demand factors.

 

[Little Bill]

I disagree. As Conduit said above note 4 states the branch circuit load for a single oven or cooktop shall be the nameplate rating of the appliance. If you connect multiple appliances to a single branch circuit then you can use the demand factors.

I sort of disagree with you Curt. The OP didn't say what kind of cooking equipment, so if it is a range, note 4 says you can use Table 220.55, and that says for 1 appliance you can use 80% demand factor. If it is 1 wall mntd. oven or 1 counter-mntd. cooking unit, then you have to use the nameplate. Or 1 counter-mnt and not more than 2 ovens, you can add the nameplates and count them as 1 range.

 

[curt swartz]

I sort of disagree with you Curt. The OP didn't say what kind of cooking equipment, so if it is a range, note 4 says you can use Table 220.55, and that says for 1 appliance you can use 80% demand factor. If it is 1 wall mntd. oven or 1 counter-mntd. cooking unit, then you have to use the nameplate. Or 1 counter-mnt and not more than 2 ovens, you can add the nameplates and count them as 1 range.

Bill, in post 4 the OP used a single oven as the example. That was the reason for my reply.

 

[Smart $]

Bill, in post 4 the OP used a single oven as the example. That was the reason for my reply.

He said oven, yes. Could assume a wall-mounted oven... or some people say oven when they mean range. So I say all bases covered

 

[Little Bill]

Bill, in post 4 the OP used a single oven as the example. That was the reason for my reply.

Sorry, I didn't notice that post.