Commercial Oven a Continuous Load

[czarjam]

We are installing a 208V 3Ph 189A commercial oven in our dining facility. Our engineers state it is a continuous load of 236 amps requiring 250A CB and 250's. We electricians say nameplate rating, non continuous 189A requiring 4/0 and 200A breaker. Just curious where we stand. Thanks in advance for your input.

 

[iwire]

We are installing a 208V 3Ph 189A commercial oven in our dining facility. Our engineers state it is a continuous load of 236 amps requiring 250A CB and 250's. We electricians say nameplate rating, non continuous 189A requiring 4/0 and 200A breaker. Just curious where we stand. Thanks in advance for your input.

It would be very helpful if you could provide the make and model of the oven.

 

[iwire]

I do not believe there is any NEC requirement to treat this as a continuous load like there is for say electric storage water heaters.

As far as choosing to treat it as one is certainly allowed and if the engineer is in charge they can certainly decide to do so.

Here is the NEC definition of continuous load

Continuous Load. A load where the maximum current is
expected to continue for 3 hours or more.

To me an oven would not fit that description as an oven cycles many times during three hours.

However an engineer can certainly choose to be conservative and decide to treat it as a continuous load.

 

[Dennis Alwon]

I agree with Bob .. Usually these ovens would not be on at 100% since they have T-stats that cycle them on and off. In fact Tale 220.56 clearly states 100% for kitchen equipment other than a dwelling

 

[david]

We are installing a 208V 3Ph 189A commercial oven in our dining facility. Our engineers state it is a continuous load of 236 amps requiring 250A CB and 250's. We electricians say nameplate rating, non continuous 189A requiring 4/0 and 200A breaker. Just curious where we stand. Thanks in advance for your input.

Did your engineers state that it is a continuous load of 236 amps requiring 250's.

or did your engineers state it is a continuous load of 236 amps requiring 250A CB and 250's.

you state the name plate rating to be 189 amps.(non-continuous)

 

[Strathead]

We are installing a 208V 3Ph 189A commercial oven in our dining facility. Our engineers state it is a continuous load of 236 amps requiring 250A CB and 250's. We electricians say nameplate rating, non continuous 189A requiring 4/0 and 200A breaker. Just curious where we stand. Thanks in advance for your input.

Just out of curiosity, why do you feel you need 4/0 wire to feed the oven, when 3/0 is rated 200A at 75 degrees?

 

[david]

Just out of curiosity, why do you feel you need 4/0 wire to feed the oven, when 3/0 is rated 200A at 75 degrees?

Alum or copper?

 

[Strathead]

Alum or copper?

Copper, aluminum would need to be 250 for 200 amps.

 

[david]

Copper, aluminum would need to be 250 for 200 amps.

i agree i miss spoke,most likely he is not mix matching in is statement between Alum and copper, also with the stated load of 189 amps Alum 4/O does not work

 

[infinity]

I agree with Bob and Dennis, non-continuous according to the NEC.

 

[david]

I agree with Bob and Dennis, non-continuous according to the NEC.

I agree with that as well, my question was intended to address increasing the over current protection.

I was wondering if the OP was sure the engineers indicated to increase both. I think I would verify they met to increase the overcurrent protection before I upsized to a 250 amp breaker

 

[czarjam]

This is the Aussie Brochure, Our oven is 68KW, 208V 3 phase 60Hz

This is the Aussie Brochure, Our oven is 68KW, 208V 3 phase 60Hz

http://www.rationalaustralia.com.au/download/SCC202E.pdf

Rational SCC 202E 20x2/1 GN We are in OCONUS, but our installation is on NEC system.

David, 3/0 copper would be perfect, my bad.

SCC 202E 20x2/1 GN68KW 208V 3Ph 60Hz

68000/360=188.8A

189x1.25(continuous load)=236A

So engineers said 250 Kcmil on 250A circuit breaker.

Our head engineer conceded our point today saying they had not considered the T stat.

Thanks for the input its great to discuss these among our team and your input is much appreciated.

I'll get my facts up straight next time ; )

 

[david]

Just out of curiosity, why do you feel you need 4/0 wire to feed the oven, when 3/0 is rated 200A at 75 degrees?

David, 3/0 copper would be perfect, my bad.

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