Electric baseboard heater circuit sizing

KVA

Senior Member
Location
United States
Correct me if I'm wrong here. The max wattage elec baseboard heat you can have on a 20a 240v circuit is 3000 watts?

3000w/240v =12.5a x 1.25 (continuous load) 15.62a That is about 80% of breaker rating. Anymore wattage will take you over the 80% OCP rule right?
 

GoldDigger

Moderator
Staff member
Location
Placerville, CA, USA
Occupation
Retired PV System Designer
Why is it a continuous load?
Fixed electric space heating is by rule a continuous load.
Is baseboard heat fixed electric space heating?

The thermostat may lead to a less than 100% duty cycle most of the time, but on a cold day, when turned on in the morning after being set back for the night, or if undersized, three hours seems to be "expected".


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Last edited:

suemarkp

Senior Member
Location
Kent, WA
Occupation
Engineer
Or the other way around: 240*20*.8 = 3840W. That is the largest heater you can run on a 240V 20A circuit. The 125%/80% factor is applied once -- you can use 100% of a breaker if the 125% continuous factor is used.
 

Sierrasparky

Senior Member
Location
USA
Occupation
Electrician ,contractor
so what do you do in the old days when the heaters were installed without the 125 percent rule.in the circuit was maxed out. 3 15 heaters on a 20 amp. Don't you get to use the wire ampacity since this is not a receptacle.

Then what do you do when the NEW has reduced the ampacity from when the place was built
 

Sierrasparky

Senior Member
Location
USA
Occupation
Electrician ,contractor
so what do you do in the old days when the heaters were installed without the 125 percent rule.in the circuit was maxed out. 3 15 heaters on a 20 amp. Don't you get to use the wire ampacity since this is not a receptacle.

Then what do you do when the NEW has reduced the ampacity from when the place was built


so much for the speak and text on my new phone.


What I meant is how do you handle heater hangeouts on an existing circuit. say 3 1500 watt units on a 20 amp cir breaker in in each of three different rooms.

:?
 

infinity

Moderator
Staff member
Location
New Jersey
Occupation
Journeyman Electrician
so much for the speak and text on my new phone.


What I meant is how do you handle heater hangeouts on an existing circuit. say 3 1500 watt units on a 20 amp cir breaker in in each of three different rooms.

:?
3-1500 watt units is still only 18.75 amps, add in a little voltage drop and the current may be even less. Although it's not complaint it will probably work indefinitely on a 20 amp circuit.
 
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