O.c.p. On range

[TODD B.]

I have a range in a residential dwelling with a 10.8 kw nameplate rating. The panel is a ITE Pushmatic, the terminal temperature is AL/CU 40 degrees on the circuit breaker. My question is with a 10.8 kw divided by 240v = 45 Amps which is a 50Amp o.c.p.d.Table 220.55 allows me to use Column C at a demand factor of 8; 8000kw divided by 240v =33Amps which allows me a 40Amp o.c.p.d. Using Table 310.16 Tells me that #8 cu thwn gives me a 50 amp capacity or #6 al thwn, and 40Amp capacity for #8 cu at 60 degrees or #6 al at 60 degrees. My confusion lies with the terminal rating of 40 degrees on the ITE circuit breaker, can i use an o.c.p.d. at 40 or 50 Amps?

 

[Smart $]

Are you certain the "40 degrees" is the termination temperature rating?

Got a picture of this labeling?

 

[Smart $]

Don't have a 40A, but here's a pic of a 20...

The 20 below ALCU is the breaker rating, not the termination temperature rating.

 

[TODD B.]

Yes, the breaker is not stamped like the one in the photo, it has an affixed label marked 40 degrees, and i propose a 2p 50a circuit breaker based on the 10.8 kw rating

 

[infinity]

The 40? is not the terminal temperature rating but the ambient calibration temperature for the trip setting.

 

[Dennis Alwon]

What wiring method are you using to get 50 amps on a Number 8 wire? 40 amp breaker is all you need.

 

[TODD B.]

Dennis, i was proposing #8 Cu thwn,thhw good for 50 amps since the nameplate of the range was 10.8 kw. Under Table 220.55 Column C IT states a demand factor of 8 which would allow me to reduce my kw to 8000, which would put me at 33.3 amps and a 40 Amp o.c.p.d. Is that what you are inquiring about? Would a 50 range receptacle still be nema configured for a 40 amp range receptacle (4-wire)?

 

[Jim W in Tampa]

Dennis, i was proposing #8 Cu thwn,thhw good for 50 amps since the nameplate of the range was 10.8 kw. Under Table 220.55 Column C IT states a demand factor of 8 which would allow me to reduce my kw to 8000, which would put me at 33.3 amps and a 40 Amp o.c.p.d. Is that what you are inquiring about? Would a 50 range receptacle still be nema configured for a 40 amp range receptacle (4-wire)?

Demand factor is for load calcs only

 

[infinity]

Dennis, i was proposing #8 Cu thwn,thhw good for 50 amps since the nameplate of the range was 10.8 kw. Under Table 220.55 Column C IT states a demand factor of 8 which would allow me to reduce my kw to 8000, which would put me at 33.3 amps and a 40 Amp o.c.p.d. Is that what you are inquiring about? Would a 50 range receptacle still be nema configured for a 40 amp range receptacle (4-wire)?

Yes a 50 amp single receptacle is permitted on a 40 amp circuit.

210.21 Outlet Devices.
Outlet devices shall have an ampere rating that is not less than the load to be served and shall comply with 210.21(A) and (B).
(B) Receptacles.
(1) Single Receptacle on an Individual Branch Circuit. A single receptacle installed on an individual branch circuit shall have an ampere rating not less than that of the branch circuit.
Exception No. 1: A receptacle installed in accordance with 430.81(B).
Exception No. 2: A receptacle installed exclusively for the use of a cord-and-plug-connected arc welder shall be permitted to have an ampere rating not less than the minimum branch-circuit conductor ampacity determined by 630.11(A) for arc welders.

 

[kwired]

110.14(C)(1) tells us that the temperature rating is 60 DEG C unless otherwise marked for devices rated 100 amp or less or termination for 14 AWG to 1 AWG.

Breakers with a 40 DEG marking on them is the ambient temperature rating of the breaker not the termination rating. If installed in an ambient temperature of over 40 DEG you need to derate the breaker which is completely separate issue from derating the conductor.

Many older breakers did not have termination temp rating marked on them and that meant 60 automatically applied as according to 110.14(C)(1), or 75 automatacilly applied if over 100 amps. Most if not all new breakers are rated 75 DEG termination and are marked so.

 

[infinity]

Demand factor is for load calcs only

Jim,
Do you have anything to back that statement up? What do you think of this?

______________________________________________________________
2-346 Log #3521 NEC-P02 Final Action: Reject
(Table 220.55, Note 4)
_______________________________________________________________
Submitter: Tim Henry, Code Electrical Classes Inc.
Recommendation: Delete the first sentence of Note 4 of Table 220.55
4. Branch Circuit Load. It shall be permissible to compute the branch circuit
load for one range in accordance with Table 220.55.
Substantiation: This is the only place in the NEC that allows a demand factor
to be applied to a branch circuit. Table 220.55 permits a reduction to the
connected load of household cooking equipment on feeders and service
entrance conductors based on not all the cooking equipment being on at the
same time in an apartment complex which makes sense. But to allow a
reduction of a single range on a branch circuit is encouraging a future violation
of the NEC. As an example: by using Note 4 for sizing a branch circuit to a
single 12kw household electric range the 12kw range is permitted to be
reduced to 8kw. 8000 watts / 240 volts = 33.3 amperes versus the nameplate of
the range which would be 12,000 watts / 240 volts = 50 amperes. Instead of
being wired to the nameplate connected load using a #6 conductor the NEC
permits this single range to be installed with a #8 conductor on a 40 ampere
circuit breaker. I also understand that in general not all 4 burners on the cook
top and the oven are on at the same time. But what about in the case of
Thanksgiving dinners when all 4 burners and the oven can be turned on at the same time and full current is drawn until the oven has reached its preset temperature. We now have sized our conductor and circuit breaker based on an
33.3 ampere load versus the 50 ampere load we now have. The violation of the
NEC now occurs when the serviceman replaces the 40 ampere breaker with a
50 ampere breaker protecting a #8 wire.
Panel Meeting Action: Reject
Panel Statement: There is no substantiation that the current rule is resulting in
branch circuits that are undersized for the application. The range is not a
continuous load.
Number Eligible to Vote: 12
Ballot Results: Affirmative: 12

_______________________________________________________________

 

[Jim W in Tampa]

Jim,
Do you have anything to back that statement up? What do you think of this?

_______________________________________________________________

Can not see how your using that for this purpose. They are talking about service feeders and load cals. A 12kw load is still just that. If I have 2 ranges (and do need them) each one still needs wire sized to carry it. The total is lower because of unlikely use but everything is still protected at the main breaker.

 

[iwire]

Can not see how your using that for this purpose. They are talking about service feeders and load cals. A 12kw load is still just that. If I have 2 ranges (and do need them) each one still needs wire sized to carry it. The total is lower because of unlikely use but everything is still protected at the main breaker.

Can you post a code section to back that up?

 

[Jim W in Tampa]

Can you post a code section to back that up?

Can you post one that say demand factor can be used to lower the needed amps on a load

 

[infinity]

What about note #4?

T220.55-Note 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.

 

[iwire]

Can you post one that say demand factor can be used to lower the needed amps on a load

220.55 Electric Ranges and Other Cooking Appliances
— Dwelling Unit(s). The load for household electric
ranges, wall-mounted ovens, counter-mounted cooking
units, and other household cooking appliances individually
rated in excess of 13⁄4 kW shall be permitted to be calculated
in accordance with Table 220.55. Kilovolt-amperes
(kVA) shall be considered equivalent to kilowatts (kW) for
loads calculated under this section.
Where two or more single-phase ranges are supplied by
a 3-phase, 4-wire feeder or service, the total load shall be
calculated on the basis of twice the maximum number connected
between any two phases.

Don't say this does not apply as the ROP Rob posted proves that it does.

 

[jumper]

Would this apply?

422.10 Branch-Circuit Rating. This section specifies the
ratings of branch circuits capable of carrying appliance current
without overheating under the conditions specified.
(A) Individual Circuits. The rating of an individual
branch circuit shall not be less than the marked rating of the
appliance or the marked rating of an appliance having combined
loads as provided in 422.62...........

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).

 

[Smart $]

Would this apply?

422.10 Branch-Circuit Rating. This section specifies the
ratings of branch circuits capable of carrying appliance current
without overheating under the conditions specified.
(A) Individual Circuits. The rating of an individual
branch circuit shall not be less than the marked rating of the
appliance or the marked rating of an appliance having combined
loads as provided in 422.62...........

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).

Follow up...

210.19 Conductors ? Minimum Ampacity and Size.
(A) Branch Circuits Not More Than 600 Volts.
...
(3)Household Ranges and Cooking Appliances. Branch-circuit
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.
...

 

[TODD B.]

I think at this point, it is confusing as others have commented. Sometimes trying to figure out the code can be difficult and i do appreciate all the comments and help from this site. I find it helpful from all who work in this field in one form of another to discuss code related issues very helpful. It seems that based on the original post that a 40 Amp o.c.p.d. is the answer for a single family home with one range using Table 220.55 Column C. Thanks for all the replies.