Cooking Residential

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wmeek

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Texas
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Electrician
Is Note 4 in table 220-55 telling me that if I have a 10KW oven and a 9KW cooktop, I can add them together . If so I have 19kw - 12kw = 7kw x 5%= 35%, then I go to table 220-55 Column C for 1 appliance =8kw x 135%=10,800 divided by 240V= 45A goes up to a 50A circuit for both units. Then i can tap j-box with a #8 romex to feed 9kw unit. Then take 10kw unit and tap j-box with a #6 romex. Is this correct.

Thanks
 
wmeek said:
Is Note 4 in table 220-55 telling me that if I have a 10KW oven and a 9KW cooktop, I can add them together . If so I have 19kw - 12kw = 7kw x 5%= 35%, then I go to table 220-55 Column C for 1 appliance =8kw x 135%=10,800 divided by 240V= 45A goes up to a 50A circuit for both units. Then i can tap j-box with a #8 romex to feed 9kw unit. Then take 10kw unit and tap j-box with a #6 romex. Is this correct.

Thanks
Click to expand...

I never feed a range and cooktop like that, however, it seems you got it right except the taps can both be done in #8 copper and you follow the tap rules. I am not sure but that is what I think. Individually the 10kw or the 9 kw can be treated as 8 kw ---- Table 220.55 -- 8000/240= 33.333 amps. #8 wire

Also there is a 45 amp circuit breaker but I believe the 50 is the better call. Hope I don't get killed on this post.
 
Dennis Alwon said:
Individually the 10kw or the 9 kw can be treated as 8 kw ---- Table 220.55 -- 8000/240= 33.333 amps. #8 wire
Click to expand...

I'm not sure about this. They certainly can't use the Table 220.55 if they were on individual circuits (read note 4 of the table), so I would think that would apply to the tap as well.
 
So your saying the taps need to be sized for the nameplate kw and not table 220-55 Col. C
 
paul32 said:
I'm not sure about this. They certainly can't use the Table 220.55 if they were on individual circuits (read note 4 of the table), so I would think that would apply to the tap as well.
Click to expand...

Note 4 First sentence--- It shall be permissible to calculate the branch circuit load for one range in accordance with Table 220.55. Am I missing something again.
 
About 210.19(A)(3), the exception allows taps but gives a minimum size and also they need to be big enough for the load (which is the question here). Can you apply table 220.55 for these tap conductors? I think not as I said above.


Dennis Alwon said:
Note 4 First sentence--- It shall be permissible to calculate the branch circuit load for one range in accordance with Table 220.55. Am I missing something again.
Click to expand...
Keep reading note 4. We don't have a range here, we have an oven and a cooktop. Note 4 lets us take them as a range TOGETHER, but if they are separate, the nameplace must be used.
 
paul32 said:
About 210.19(A)(3), the exception allows taps but gives a minimum size and also they need to be big enough for the load (which is the question here). Can you apply table 220.55 for these tap conductors? I think not as I said above.
Keep reading note 4. We don't have a range here, we have an oven and a cooktop. Note 4 lets us take them as a range TOGETHER, but if they are separate, the nameplace must be used.
Click to expand...

So lets look at this. You agree the load can be used as calculated 45 amps??? If so that's a #6 wire for both but I would still have to pull a #6 to just the 10kw unit. That's bizarre. Or a you saying the whole calculation is wrong and has to be at 100% of nameplate??
 
One thing that seems odd about this whole thing. If the oven were 13kw, by itself it would need 54A. But combine it with a 9KW cooktop, the total of 22 kw would be 12kw from the table which needs 50A. The oven would need a larger branch circuit if it were by itself than if together with the cooktop. :cool:
 
wmeek said:
So your saying the taps need to be sized for the nameplate kw and not table 220-55 Col. C
Click to expand...
I read your OP again, and that seems to be what you did to start with. I agree with that. The tap rules are letting you use the 8 for the cooktop.
 
I feel the reasoning is there is little doubt that both oven and cooktop will be a maxiumum peak at the same time.
 
But i do see it as sizing the taps for nameplate KW, just in case you were to max out one appliance at a time
 
220.55

220.55

I would have to say that no matter what formula you use the calculated load for the branch circuit would be 11 KW. 11 KW divided by 240 Volts would give you 45.8 amps. Branch circuit should be a #6 AWG OCPD would be 50 amps. taps would be as stated in 210.19.
 
paul32 said:
One thing that seems odd about this whole thing. If the oven were 13kw, by itself it would need 54A. But combine it with a 9KW cooktop, the total of 22 kw would be 12kw from the table which needs 50A. The oven would need a larger branch circuit if it were by itself than if together with the cooktop. :cool:
Click to expand...

The 13 kW oven is a cooking appliance, and the "Range" rules of Table 220.55 apply. Therefore it would need a branch circuit for 8kW(1+(13-12)*.05) = 8.4 kW==>35 Amps.
 
Bob NH said:
The 13 kW oven is a cooking appliance, and the "Range" rules of Table 220.55 apply. Therefore it would need a branch circuit for 8kW(1+(13-12)*.05) = 8.4 kW==>35 Amps.
Click to expand...
The "range" rules DON'T apply to the branch circuit to just an oven. That is my point, you might need a larger branch circuit for the oven alone (at nameplate) than if you combine it with a cooktop (treated like a range).

Read note 4 of table 220.55 closer:

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. ...
 
I think the difference lies in the fact that a single oven (usually) has two heat elements, the upper and lower oven elements.
If you turn the oven on "preheat", both elements will energize and it will pull close to it's rated KW.
A typical range has 6 heat elements....4 stove eyes and 2 oven elements.
To turn all of them on at the same time requires the user to turn on at least 5 switches. That's not likely, unless they're using it for heat.
IMO...that's why it's allowed to size a range circuit per 220.55

The 16KW range that I talked about in another post has two seperate elements in each stove eye (large/small) and you can't turn them both on at the same time, but I believe that both elements (for each of 4 eyes) are included in the 16KW rating.
It seems like the manufacturer adds all of the heating elements together to get the KW rating even though it's not possible to use them all at the same time.
just my opinion.
steve
 
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