4000 watt wall heater on #12 Nm 20 amp circuit

[Sierrasparky]

What do you think about a electric wall heater 4000 watts fed from a dedicated 12 guage 20 amp circuit?
Nec says continuous and I calculate 16.67 amps X 1.25% +20.84 amps can ypu still use a 20 amp circuit. I am seeing this quite often done. However does it comply if you replace with a new and different heater?

Thanks

 

[iwire]

Looks like no can do, your fractions are more than 0.5

220.5 Calculations.

(B) Fractions of an Ampere. Calculations shall be permitted
to be rounded to the nearest whole ampere, with decimal
fractions smaller than 0.5 dropped.

 

[jumper]

No relief from the small breaker rule for this app.

424.22 Overcurrent Protection.
(A) Branch-Circuit Devices. Electric space-heating equipment,
other than such motor-operated equipment as required
by Articles 430 and 440 to have additional overcurrent protection,
shall be permitted to be protected against overcurrent
where supplied by one of the branch circuits in Article 210.

 

[K8MHZ]

If the heater had a timer that could not be set for more than three hours would that make it a non-continuous load?

 

[Cow]

I think I'd see if I could swap the guts to a 3500w heater. If it's a Pick-a-watt or Cadet heater, you might get lucky.

 

[GlennH]

Maybe you have 245 volts?

 

[peter d]

If the heater had a timer that could not be set for more than three hours would that make it a non-continuous load?

Negative, the 125% rule applies to electric space heating equipment without exception.

 

[Dennis Alwon]

Maybe you have 245 volts?

The reality of the situation is probably just that- 245V or 244 either of which would allow the 20 amp circuit. Problem is that 244-245V, even if measured, may not always be that high and cannot be used. That really stinks. The manufacturer should make the units work on 240V on a 20 amp cir.-- a 3840 watt heater...

I assume the voltage at the building is 240V.

 

[iwire]

The reality of the situation is probably just that- 245V or 244 either of which would allow the 20 amp circuit.

The reality is it would draw more current at 244 or 245 volts.

 

[Sierrasparky]

Thanks, Going to replace with a 3000 w unit.

 

[iwire]

Thanks, Going to replace with a 3000 w unit.

Shorten the element in the field.

 

[kwired]

Shorten the element in the field.

Wouldn't that make less resistance = more current @ same voltage?

 

[Dennis Alwon]

The reality is it would draw more current at 244 or 245 volts.

yep.. I got lost in the post I quoted going in that direction- doh.

 

[iwire]

Wouldn't that make less resistance = more current @ same voltage?

Yeah, I was just testing you all to see if you were paying attention.








:ashamed1::ashamed1: :slaphead:

 

[iwire]

yep.. I got lost in the post I quoted going in that direction- doh.

It is just one of those weird things, I was thinking fudge the voltage as well.

 

[Little Bill]

The reality is it would draw more current at 244 or 245 volts.

:? 4000/240=16.67A, 4000/244=16.39, 4000/245=16.32
How is that drawing more current?:?

 

[infinity]

:? 4000/240=16.67A, 4000/244=16.39, 4000/245=16.32
How is that drawing more current?:?

Because your math is incorrect. The 4000 watts is at one specific voltage. If you change the voltage you would change the wattage. You need to first find the resistance at the heater's rated voltage and then use that in your calcuation along with the voltage to determine the current.

 

[Little Bill]

Because your math is incorrect. The 4000 watts is at one specific voltage. If you change the voltage you would change the wattage. You need to first find the resistance at the heater's rated voltage and then use that in your calcuation along with the voltage to determine the current.

Nothing wrong with my math, I'm using a brand new "Dollar Store" calculator.:lol: All my divisions are correct. Mis-applied maybe, but correct.:slaphead:

 

[Sierrasparky]

Shorten the element in the field.

That would void the listing

 

[Cow]

That would void the listing

He was joking....? Do you see the wink?