# 9 kw oven



## Julius793 (Nov 29, 2011)

my manager told me i will be installing a 9kw oven 240v tomorrow and i should find out what size the circuit needs to be. to which i responded 9000w/240v=37.5a so a 40a circuit. to which he stated thats not correct because ovens have a special code.:no: can anyone explain to me what he means? or does he not know the nec?


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## McClary’s Electrical (Feb 21, 2009)

Julius793 said:


> my manager told me i will be installing a 9kw oven 240v tomorrow and i should find out what size the circuit needs to be. to which i responded 9000w/240v=37.5a so a 40a circuit. to which he stated thats not correct because ovens have a special code.:no: can anyone explain to me what he means? or does he not know the nec?


 *
(3) Household Ranges and Cooking Appliances.​*​​​​Branchcircuit
conductors supplying household ranges, wallmounted
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 83⁄4 kW or
more rating, the minimum branch-circuit rating shall be 40​
amperes.


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## tsr341 (May 22, 2012)

Ranges are have a demand factor. For residential ranges you would apply table 220.55. of the 2011 nec. Also if it is a commercial range you would have to apply the 125% continuous load factor.


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## Dennis Alwon (May 9, 2009)

For household Ranges look at Table 220.55


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## Dennis Alwon (May 9, 2009)

tsr341 said:


> Ranges are have a demand factor. For residential ranges you would apply table 220.55. of the 2011 nec. Also if it is a commercial range you would have to apply the 125% continuous load factor.


Can you provide an article with that info about the commercial range.


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## TooFarFromFenway (Jul 15, 2011)

220.56 in the 2008 NEC is the table I think that should be used.


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## Dennis Alwon (May 9, 2009)

TooFarFromFenway said:


> 220.56 in the 2008 NEC is the table I think that should be used.


If it is install in a non dwelling


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## Julius793 (Nov 29, 2011)

Dennis Alwon said:


> For household Ranges look at Table 220.55


 isnt that only for load calculations?


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## Dennis Alwon (May 9, 2009)

Julius793 said:


> isnt that only for load calculations?


That is an argument I won't get into. I don't know the answer to that and I don't believe anyway else has ever gotten an answer to that. It doesn't change much since you would still use a 40 amp circuit either way.

IMO, I believe it is for calculations but I have heard it argued both ways. The art. states the load shall be calculated in accordance with the table. The load is what I wire for.


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## tsr341 (May 22, 2012)

Dennis Alwon said:


> Can you provide an article with that info about the commercial range.


art 422.10 (A) "The branch-circuit rating for an appliance that is a continuous
load, other than a motor-operated appliance, shall
not be less than 125 percent of the marked rating, or not
less than 100 percent of the marked rating if the branchcircuit
device and its assembly are listed for continuous
loading at 100 percent of its rating.
Branch circuits and branch-circuit conductors for household
ranges and cooking appliances shall be permitted to be in
accordance with Table 220.55 and shall be sized in accordance
with 210.19(A)(3)."

Also to show continuous load you could look at art 220.56 "Kitchen Equipment — Other Than Dwelling
Unit(s). It shall be permissible to calculate the load for
commercial electric cooking equipment, dishwasher
booster heaters, water heaters, and other kitchen equipment
in accordance with Table 220.56. These demand factors
shall be applied to all equipment that has either thermostatic
control or intermittent use as kitchen equipment.
These demand factors shall not apply to space-heating, ventilating,
or air-conditioning equipment.
However, in no case shall the feeder or service calculated
load be less than the sum of the largest two kitchen
equipment loads."


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## Julius793 (Nov 29, 2011)

Dennis Alwon said:


> That is an argument I won't get into. I don't know the answer to that and I don't believe anyway else has ever gotten an answer to that. It doesn't change much since you would still use a 40 amp circuit either way.
> 
> IMO, I believe it is for calculations but I have heard it argued both ways.


 well thanx havent been around long enough to know that it can be argued both ways i guess


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## pistol pete (Jul 4, 2011)

I may be mauled for saying this but keeping it simple hell with charts. One doesnt wanna use more than 80% of any circuit under normal circumstances and 80% of a 40 amp circuit is 32 amps ... so no good.. the 125 % rule is more useful for motor loads but is still useful to elminate more than 80% of a circuit being used...


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## Dennis Alwon (May 9, 2009)

tsr341 said:


> art 422.10 (A) "The branch-circuit rating for an appliance that is a continuous
> load, other than a motor-operated appliance, shall
> not be less than 125 percent of the marked rating, or not
> less than 100 percent of the marked rating if the branchcircuit
> ...


So show me where it states a range is a continuous load. Ranges have thermostats and cycle on and off. It could never be on for 3 hours at a time.

Do you see the demand factor for 1 range in T. 220.56-- 100% not 125%


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## Dennis Alwon (May 9, 2009)

pistol pete said:


> I may be mauled for saying this but keeping it simple hell with charts. One doesnt wanna use more than 80% of any circuit under normal circumstances and 80% of a 40 amp circuit is 32 amps ... so no good.. the 125 % rule is more useful for motor loads but is still useful to elminate more than 80% of a circuit being used...


Pete- that is not true. Breakers are rated at 100% unless they are on continuously (3 hours or more) so if the load is 100% of the breaker and is not on for more than 3 hours at a time then there is nothing wrong with it. 

There are breakers that are actually made for continuous duty as well.


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## pistol pete (Jul 4, 2011)

Dennis Alwon said:


> Pete- that is not true. Breakers are rated at 100% unless they are on continuously (3 hours or more) so if the load is 100% of the breaker and is not on for more than 3 hours at a time then there is nothing wrong with it.
> 
> There are breakers that are actually made for continuous duty as well.


Yes they are but any breaker at 98% everything starts to get warm wire the breaker its just not good stuff... and what happens when the 25lb thanksgiving turkey goes in for 6 hours... just trying to pass on sound basic load calculations.. and i would guess the OP might be thinking 8 wire with a 40amp even 50 amp curcuit ... just use 6/ 3 and do the "right" IMO job


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## McClary’s Electrical (Feb 21, 2009)

pistol pete said:


> Yes they are but any breaker at 98% everything starts to get warm wire the breaker its just not good stuff... and what happens when the 25lb thanksgiving turkey goes in for 6 hours... just trying to pass on sound basic load calculations.. and i would guess the OP might be thinking 8 wire with a 40amp even 50 amp curcuit ... just use 6/ 3 and do the "right" IMO job


 
You can leave your stove on for 6 hrs, 12 hrs, or 12 days, and it is still not a continuous load.


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## electricmanscott (Feb 11, 2010)

pistol pete said:


> Yes they are but any breaker at 98% everything starts to get warm wire the breaker its just not good stuff... and what happens when the 25lb thanksgiving turkey goes in for 6 hours... just trying to pass on sound basic load calculations.. and i would guess the OP might be thinking 8 wire with a 40amp even 50 amp curcuit ... just use 6/ 3 and do the "right" IMO job


So tell us what happens when the 25 pound turkey goes in for six hours?


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## pistol pete (Jul 4, 2011)

electricmanscott said:


> So tell us what happens when the 25 pound turkey goes in for six hours?


Well afterwards its dinner time ...!


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## Speedy Petey (Jan 10, 2007)

pistol pete said:


> Yes they are but any breaker at 98% everything starts to get warm wire the breaker its just not good stuff...


SO??

That does not change the fact that a breaker is rated for *100%* of it's rating. PERIOD. 

You can say to hell with charts, I'm doing it my way, but that is like saying _"To hell with the NEC. I'm gonna just over build everything so I'm covered."_


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## Jlarson (Jun 28, 2009)

pistol pete said:


> just use 6/ 3 and do the "right" IMO job


Do you pay for the "right" wire yourself, or do you make the client pay for bigger wire then they need just cause you like to over build?


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## pistol pete (Jul 4, 2011)

Why but of course pass on the spending... i was being a little rash with the hell with the chart... lazy too... i was only trying to pass on basic safe general rules of thumb.. and if you have a 99 percent load on a new breaker for more than a second or two youve got probloms ..


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## Speedy Petey (Jan 10, 2007)

pistol pete said:


> .. and if you have a 99 percent load on a new breaker for more than a second or two youve got probloms ..


Do you HONESTLY believe this??


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## Jlarson (Jun 28, 2009)

pistol pete said:


> i was only trying to pass on basic safe general rules of thumb..


No, you're passing on poor design skills and practices. 

There is absolutely nothing wrong with a 40 amp circuit in this application, nor is there anything wrong with the breaker getting a little "warm". 

It will have no problem holding 100% load at temperatures far above average room temp in fact.


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## TooFarFromFenway (Jul 15, 2011)

Dennis Alwon said:


> So show me where it states a range is a continuous load. Ranges have thermostats and cycle on and off. It could never be on for 3 hours at a time.
> 
> Do you see the demand factor for 1 range in T. 220.56-- 100% not 125%


It COULD be on constantly, or at least pretty close to that, in a busy restaurant like a Texas Roadhouse, or Red Lobster, etc. 

Most places, you're most likely right though. 

Now, I could be wrong on this, but I think a convection oven cycles the heating element on and off more often than a conventional oven, so the cycles of on/off are much shorter. 

But, I have a more serious question......

What kind of restaurant uses an electric range in a restaurant anyway? Gas is the way to go. MUCH more efficient than electric IMO. 

Maybe we can contact Vulcan or some other manufacturer to see what they recommend?


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## I_get_shocked (Apr 6, 2009)

220.55 note 4 allows you to use table 220.55 to calculate the *branch circuit* load.

210.23a1 says Utilization equipment not fastened in place shall not exceed 80% of the branch circuit ampere rating. 

Is the range fastened in place?

422.10 a The rating of an individual branch circuit shall not be less than the marked rating of the appliance


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## MDShunk (Jan 7, 2007)

Jlarson said:


> No, you're passing on poor design skills and practices.
> 
> There is absolutely nothing wrong with a 40 amp circuit in this application, nor is there anything wrong with the breaker getting a little "warm".
> 
> It will have no problem holding 100% load at temperatures far above average room temp in fact.


In fact, that 40 amp breaker will hold at 45 amps for 2.7 hours by most common miniature circuit breaker time-current curves.


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## BBQ (Nov 16, 2010)

TooFarFromFenway said:


> It COULD be on constantly, or at least pretty close to that, in a busy restaurant like a Texas Roadhouse, or Red Lobster, etc.


No, it could not be unless it is broken. 

No matter how busy the restaurant is the equipment still cycles.


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## noarcflash (Sep 14, 2011)

What happens when you put that double wall over into SELF CLEANING MODE, and it draws max current for 8 hours........................... ??


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## Dennis Alwon (May 9, 2009)

The fact is that even 8 hours a few times of the year would not be an issue. Also do your really think that the oven is on full steam for 8 hrs???? It has a thermostat and a maximum temp rating.


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## noarcflash (Sep 14, 2011)

We just self cleaned our oven last week. the next time we do it, I will measure current draw, and breaker temp.

Self cleaning mode is pretty hot. the entire house heats up, and stinks out. every bit of grease burns off.


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## Dennis Alwon (May 9, 2009)

noarcflash said:


> We just self cleaned our oven last week. the next time we do it, I will measure current draw, and breaker temp.
> 
> Self cleaning mode is pretty hot. the entire house heats up, and stinks out. every bit of grease burns off.


I think if that oven was on for 6 hours at maximum temp it would blow up. :thumbup: The oven when cleaning gets to 900° but it is still usually just a 3 hour job.


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## noarcflash (Sep 14, 2011)

'heavy' self cleaning mode runs 4 hours, according to my owners manual.


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## Dennis Alwon (May 9, 2009)

noarcflash said:


> 'heavy' self cleaning mode runs 4 hours, according to my owners manual.


So all this is moot since I doubt the oven is running for that entire period at full capacity. Again if you ran the oven for 4 hours once or twice a year and it was on all the time, I seriously doubt you would ever have any issues with it.


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