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Range calculation

R

retnoc

Member
Location
Sparta, nj
Occupation
Electrician
Hello everyone,

Long time follower, first time posting.
I've been in the field for over 20 years, but mostly industrial/commercial. I'm getting a lot of contradictory replies from license holders regarding the proper breaker for an electric range, and can use some assistance.

Nameplate is 208v, single phase, 91amps, 17.3kw

Using table 220.55, column C I'm seeing a demand factor of 10,260kw.

When I calculate that by 208v, I'm getting 48amps.

Would I be safe to use a 60amp breaker?

The replies I've gotten have ranged from
60-->80->125amps.

Thanks in advance.
 
roger

roger

Moderator
Staff member
Location
Fl
Occupation
Retired Electrician
Please update your profile with an accurate location.
 
Dennis Alwon

Dennis Alwon

Moderator
Staff member
Location
Chapel Hill, NC
Occupation
Retired Electrical Contractor
retnoc said:
Hello everyone,

Long time follower, first time posting.
I've been in the field for over 20 years, but mostly industrial/commercial. I'm getting a lot of contradictory replies from license holders regarding the proper breaker for an electric range, and can use some assistance.

Nameplate is 208v, single phase, 91amps, 17.3kw

Using table 220.55, column C I'm seeing a demand factor of 10,260kw.

When I calculate that by 208v, I'm getting 48amps.

Would I be safe to use a 60amp breaker?

The replies I've gotten have ranged from
60-->80->125amps.

Thanks in advance.
Click to expand...

This has always been a difficult discussion. The NEC allows you to use the table so IMO you could use a 50 or even a 60 amp circuit. I would bet some inspectors would argue and say you need 100 amps. The unit does not say minimum circuit ampacity so my gut says to allow for the 50 or 60 amps. I didn't check your calculation.....so I assume it is correct
 
Dennis Alwon

Dennis Alwon

Moderator
Staff member
Location
Chapel Hill, NC
Occupation
Retired Electrical Contractor
Sometimes I think the nec is a bit low on these calculations. Using the table a 9kw thru16kw range can all be fed with a 40 amp circuit. I am not sure I would be comfortable installing a 40 amp cir on a 16kw unit.
 
H

HEYDOG

Senior Member
retnoc said:
Hello everyone,

Long time follower, first time posting.
I've been in the field for over 20 years, but mostly industrial/commercial. I'm getting a lot of contradictory replies from license holders regarding the proper breaker for an electric range, and can use some assistance.

Nameplate is 208v, single phase, 91amps, 17.3kw

Using table 220.55, column C I'm seeing a demand factor of 10,260kw.

When I calculate that by 208v, I'm getting 48amps.

Would I be safe to use a 60amp breaker?

The replies I've gotten have ranged from
60-->80->125amps.

Thanks in advance.
Click to expand...
Is this Range in a Dwelling unit?
 
infinity

infinity

Moderator
Staff member
Location
New Jersey
Occupation
Journeyman Electrician
retnoc said:
Being a commercial kitchen, can I still apply non continuous load and install a 100amp breaker, or does this to change and require the 125%?

I appreciate the confirmation and support.
Click to expand...
A range will never run for 3 or more hours at maximum output so no on the continuous load.
 
Jpflex

Jpflex

Electrician big leagues
Location
Victorville
Occupation
Electrician commercial and residential
retnoc said:
Hello everyone,

Long time follower, first time posting.
I've been in the field for over 20 years, but mostly industrial/commercial. I'm getting a lot of contradictory replies from license holders regarding the proper breaker for an electric range, and can use some assistance.

Nameplate is 208v, single phase, 91amps, 17.3kw

Using table 220.55, column C I'm seeing a demand factor of 10,260kw.

When I calculate that by 208v, I'm getting 48amps.

Would I be safe to use a 60amp breaker?

The replies I've gotten have ranged from
60-->80->125amps.

Thanks in advance.
Click to expand...
Well I did the math and this is what I get:

NEC allows you to size the branch circuit for 1 range according to table 220.55

For 1 range over 8750 VA the minimum branch circuit would be 40 i amperes but does not apply here since you are at 17,300 watts or VA.

Therefore, 1 range use column C of table 220.55 which is 8000 watts or VA

Then your load is over 12,000 VA so add 5% increase to column C value for every 1,000 VA that 17,300 VA exceeds 12,000 VA

Answer 17,300 - 12000 = 5,300 / 1,000 (how many sets of 1,000) = 5.3

5.3 x 0.05 (5% increase) to column C value needed = 26.5% increase

Column C 8,000 x 1.265 (126 %) = 10,120 watts is your new calculated load to be applied to the feeder/ branch circuit for this range. Neutral under specific circumstances can be reduced to 70% for feeder demand.

10,120 VA / 208 E volts = 48.65 i load amperes

Branch circuit wire size = # 8 AWG THHN minimum good for 50 i amperes if terminating at 75 degrees Celsius with an ambient temperature of 30 degrees Celsius.

OCPD breaker size = 48.65 but go to next standard size up = 50 i ampere breaker

(Question for everyone else on this post is whether these figures i derived from following NEC rules include the 125% upsize for continuous load, or is this not to be considered a continuous load or does table 220.55 already include 125% for continuous load assuming range is on for more than 3 hours at max current load for Thanksgiving?)

My answer is 50 ampere 2 pole single phase breaker minimum and a # 8 AWG THHN wire
 
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