Electric Range Demand Factor

[Jerramundi]

Hey guys,

I'm correcting the improper installation of an Electric Range / Double Oven for a friend and had a question about the Demand Factors.

The range nameplate rating is 7800W 120/240V or 32.5A.... and the installation manual EXPLICITLY calls for a 40A circuit.

However w/ the permissible demand factor of 80% via NEC 220.55 (Note #3), I'm looking at 26A or a 30A circuit.

My question is, does the installation manual and manufacturer's specifications supersede the NEC and its' permissible demand factors?



Thanks in advance,

Jerramundi

 

[Dennis Alwon]

The manufacturers instructions supersedes the NEC

 

[topgone]

Hey guys,

I'm correcting the improper installation of an Electric Range / Double Oven for a friend and had a question about the Demand Factors.

The range nameplate rating is 7800W 120/240V or 32.5A.... and the installation manual EXPLICITLY calls for a 40A circuit.

However w/ the permissible demand factor of 80% via NEC 220.55 (Note #3), I'm looking at 26A or a 30A circuit.

My question is, does the installation manual and manufacturer's specifications supersede the NEC and its' permissible demand factors?



Thanks in advance,

Jerramundi

NEC is a standard! That said, the rules are the safety levels. That means you can choose a protection that errs on the safe side--> meaning, you can choose a lower setting (and suffer the consequence, if it doesn't work), never to exceed what is stipulated!

 

[Jerramundi]

The manufacturers instructions supersedes the NEC

That's what I was thinking Dennis. Thank you for confirming that.

 

[Little Bill]

Hey guys,

I'm correcting the improper installation of an Electric Range / Double Oven for a friend and had a question about the Demand Factors.

The range nameplate rating is 7800W 120/240V or 32.5A.... and the installation manual EXPLICITLY calls for a 40A circuit.

However w/ the permissible demand factor of 80% via NEC 220.55 (Note #3), I'm looking at 26A or a 30A circuit.

My question is, does the installation manual and manufacturer's specifications supersede the NEC and its' permissible demand factors?



Thanks in advance,

Jerramundi

That demand factor is for the service or feeder load, not the branch circuit. Note #4 is for branch circuits.
40A is the correct OCPD.

 

[LarryFine]

A replacement unit may require a little more in the future.

 

[kwired]

That demand factor is for the service or feeder load, not the branch circuit. Note #4 is for branch circuits.
40A is the correct OCPD.

Correct, and the reason why you have less VA per range when you have more ranges. They are betting on the fact that not all will be drawing full load amps all at the same time as this kind of appliance has multiple heating elements that individually cycle as needed. If you do turn on every element at same time you will draw max amps, but only for short time before they begin to cycle individually.

 

[Dennis Alwon]

I hate it when the manufacturers control the calculation for the branch circuit, however in this case note 4 states that you must use the nameplate rating for a cooktop--I am assuming if there is a double oven then the mentioned range is really just a cooktop and thus you must use the nameplate. Of course the manufacturer has the final say

 

[Jerramundi]

That demand factor is for the service or feeder load, not the branch circuit. Note #4 is for branch circuits.
40A is the correct OCPD.

Thank you for that correction Bill.

I mistakenly assumed Notes #1 - #3 could apply to the branch circuit, but you are right... everything from 220.40 to 220.61 IS under the Section III Heading - "Feeder and Service Load Calculations." Note #4 specifically begins with the phrasing "Branch-Circuit Loads" and further specifies that the load shall be the nameplate rating.

Thank you for pointing that out.

 

[Jerramundi]

I hate it when the manufacturers control the calculation for the branch circuit, however in this case note 4 states that you must use the nameplate rating for a cooktop--I am assuming if there is a double oven then the mentioned range is really just a cooktop and thus you must use the nameplate. Of course the manufacturer has the final say

It's a wall mounted double oven, not a cook top. Either way, thank for you for pointing out that Notes #1 - #3 don't apply to the branch circuit. That's important and I wasn't paying attention to the main section heading it's under.

Also thank you for clarifying that the manufacturer has the final say. That's what I was most curious about.

It's a really tough conduit run from the panel to below the kitchen as it's a split level with lots of existing mechanical in the way.... and I was hoping to utilize existing conduit by applying the demand factor and lowering the required wire size... but it looks like I might be stuck running a new raceway.

 

[Jerramundi]

I hate it when the manufacturers control the calculation for the branch circuit, however in this case note 4 states that you must use the nameplate rating for a cooktop--I am assuming if there is a double oven then the mentioned range is really just a cooktop and thus you must use the nameplate. Of course the manufacturer has the final say

On that note Dennis (and getting slightly off topic)... I realized I could de-rate the neutral from a #8 to a #10... and after doing some conduit fill calculations, realized I can legally pull 3 x #8 and a #10 neutral through this existing 3/4" that contains other circuits... the problem is... this existing run would utilize a section of FMC that is well over 6 ft.

I feel like the right answer is to stop looking for the easy way out and just run a new raceway... what are your thoughts about using an existing raceway that is not up to code? It's my understanding that FMC cannot be run over 6 ft in length. I don't know if this just a Chicago thing or a specific NEC rule. I know some villages around here are implementing local amendments that are even going as far as to say FMC cannot be longer than 3 ft and only be utilized for appliance disconnects.

 

[david luchini]

That demand factor is for the service or feeder load, not the branch circuit. Note #4 is for branch circuits.
40A is the correct OCPD.

Using note 4, for a range you can apply the 80% demand factor from Col B to the 7.8kW. That's a 30A circuit at 240V.

Note #4 specifically begins with the phrasing "Branch-Circuit Loads" and further specifies that the load shall be the nameplate rating.

Note 4 specifies that the branch circuit load for a range can be calculated per Table 220.55.

 

[david luchini]

It's a wall mounted double oven, not a cook top.

Is it a range or an oven? Your first post mentioned range.

 

[Jerramundi]

Is it a range or an oven? Your first post mentioned range.

I was under the impression that the term "range" referred to a combination (1) oven and (2) stove top / cook top... Perhaps I was mistaken in referring to this as a "range" and it would be better to specify it as a "wall mounted double oven."

However, given the historical context of the term "range" in that it "provided multiple places to cook (i.e. (1) the oven and (2) the stove top / cook top)... would this still not qualify as a "range" given that there are "multiple places to cook" (i.e. two ovens)??

Getting into semantics here and I'm not trying to flex. I wish to use the proper terminology. If the term "range" is incorrect that's my fault. However, i'll reiterate, given the historical context of the term's origin... I think this would qualify as a "range."

 

[Jerramundi]

Is it a range or an oven? Your first post mentioned range.

Granted this is a singular appliance consisting of two ovens... but your typical "range" is also a singular appliance consisting of two places to cook (i.e. (1) the oven and (2) the stove top / cook top). So I'm fairly certain this "wall mounted double oven" should be treated as a "range," in which case, you are correct... the first sentence of Note #4 applies and you can apply the 80% demand factor.

However, based on what Dennis said... and I agree... the manufacturer's specs supersede the NEC and I need a 40a circuit.

 

[powerpete69]

Always install the breaker size that the manufacturer tells you to install. The NEC is not privy to the internals of the unit you are referring to.
However, always refer to the NEC to size the wire for this breaker. 40 amp double pole breaker with #8 wire assuming the oven is a reasonable distance from its feeder panel.

 

[david luchini]

I was under the impression that the term "range" referred to a combination (1) oven and (2) stove top / cook top... Perhaps I was mistaken in referring to this as a "range" and it would be better to specify it as a "wall mounted double oven."

I think this is the generally accepted definition of "range." As such, your double oven would not be a range, so you couldn't apply the 80% demand factor from Column B of T220.55.

 

[Jerramundi]

Always install the breaker size that the manufacturer tells you to install. The NEC is not privy to the internals of the unit you are referring to.
However, always refer to the NEC to size the wire for this breaker. 40 amp double pole breaker with #8 wire assuming the oven is a reasonable distance from its feeder panel.

Agreed Pete. Your argument that "the NEC is not privy to the internals of the unit" is exactly why I agreed with both Dennis' first response and your comment here that the manufacturer's specs supersede the NEC. Well put that ""the NEC is not privy to the internals of the unit." Makes perfect sense.

It's about a 90ft run in wire length. I realize I'm getting up there and voltage drop comes into play, but not enough for me to be concerned about increasing the conductor size from a #8 on a 32.5A load. If it were a 38A load, I'd run the VD and see if I need to increase the wire size, but I feel confident #8 will suffice.

Interesting stipulation though that distance of the run / voltage drop could force your hand in sizing the circuit larger than the manufacturer requires. I suppose that would be a case in which the NEC beats the manufacturer's specifications

 

[Jerramundi]

I think this is the generally accepted definition of "range." As such, your double oven would not be a range, so you couldn't apply the 80% demand factor from Column B of T220.55.

Agreed that this is the "generally accepted definition" of a "range." I still think one could argue that a double oven qualifies as a "range" given the historical context / origin of the term "range" as something that "provides a range of cooking methods."

I'm suprised the NEC doesn't provide a definition given how frequently it references the term in ways that are very specific to how you can calculate the load.

Either way, I'm going with the 40A given the explicit call for it in the manufacturer's specifications and the group consensus here that said specifications supersede the NEC / permissible demand factors.

I don't want to drag this thread out any longer than it already has been, but I'd be curious how this debate about (1) NEC permissible demand factors VS. (2) manufacturer's specifications...would play out if I were installing (6) of these units

Appreciate the input brother.

 

[LarryFine]

Here's what I would do: keep the existing cable, put in a 40a breaker, and be done.

You're never going to have every element on simultaneously.