Bad combination

[krisway]

I've been asking some questions in another thread, but wanted to start fresh as I think I may have other issues. Tell me what I have done wrong

2000w and 2500w heaters in my garage hooked up to my panel with 12/2 wire and a 30amp dbl pole breaker.

I have been told that the 30amp breaker is too high for 12/2 wire. And that 4500w on a single circuit is too much.

Solution? Replace the 2500w heater with a 2000w heater and replace the 30amp breaker with a 20 amp breaker?

 

[budmur]

Having both heaters on a single circuit is the problem. Replace the 30-amp with a 20-amp double pole, then add another 20-amp double pole to separate the circuits and you should be fine.

 

[pattenp]

4500W needs to be on a 30 amp 240V circuit using #10 Cu.

Are these hard wired or plug-in heaters?

 

[krisway]

Having both heaters on a single circuit is the problem. Replace the 30-amp with a 20-amp double pole, then add another 20-amp double pole to separate the circuits and you should be fine.

My garage is already sheeted up with 1/2" plywood. And I don't have room in my panel to add another circuit breaker.

Can I run two 2000w heaters on a 20amp dbl pole breaker and 12/2 wire?

 

[pattenp]

Yes. 4000W is the absolute max you can put on #12 @ 240V.

 

[J.A.Varela]

Sounds like patten knows his stuff . Listen to his advice.

 

[krisway]

Yes. 4000W is the absolute max you can put on #12 @ 240V.

Thank you. Hopefully my last question, can I use this thermostat to control both of these heaters? See my other post for a pic of the thermostat. linky

 

[Stuart in MN]

Since that thermostat in your link is marked in Celsius only, I'm guessing you're located in Canada? It should work fine, but be aware that electrical codes in Canada aren't always the same as they are in the US - I think advice given so far is good, but you should confirm it applies where you live.

 

[pattenp]

As long as the Tstat is rated for at least 4000W at 240V then it's okay. The single-line will work on 240V. It's just breaks one line to turn off the heater. If you look at the Tstat on most portable 240V heaters it just breaks one leg.

 

[Labradorian]

Since that thermostat in your link is marked in Celsius only, I'm guessing you're located in Canada? It should work fine, but be aware that electrical codes in Canada aren't always the same as they are in the US - I think advice given so far is good, but you should confirm it applies where you live.

Being an electrical designer here in Canada, I can tell you that the Canadian electrical code and US electrical codes are VERY similar. In this situation they are the same.

By code you are not allowed to load a breaker more than 80%, for a 20A breaker that would be 16A. a 4000W load on 240V would be 16.6A. And in reality you won't have 240V, more like 235 ish. that would give you a load of over 17A.

I wouldn't worry to much about it unless you are getting it inspected. Seeing it is a resistive load you will not have any nuisance tripping.

...Im just sayin....

 

[pattenp]

This is a case where the technical numbers of the code are close but aren't an issue for when the manufactures set the amp/circuit size for their heaters. If you look at a portable 4000W 240V heater, it most likely comes with a 20A 240V cord and plug on it.

Being an electrical designer here in Canada, I can tell you that the Canadian electrical code and US electrical codes are VERY similar. In this situation they are the same.

By code you are not allowed to load a breaker more than 80%, for a 20A breaker that would be 16A. a 4000W load on 240V would be 16.6A. And in reality you won't have 240V, more like 235 ish. that would give you a load of over 17A.

I wouldn't worry to much about it unless you are getting it inspected. Seeing it is a resistive load you will not have any nuisance tripping.

...Im just sayin....

 

[justsam]

.

By code you are not allowed to load a breaker more than 80%, for a 20A breaker that would be 16A. a 4000W load on 240V would be 16.6A. And in reality you won't have 240V, more like 235 ish. that would give you a load of over 17A.

I wouldn't worry to much about it unless you are getting it inspected. Seeing it is a resistive load you will not have any nuisance tripping.

...Im just sayin....

I am not sure we can consider this heater as a constant power load, and hold 4KW constant, and assume as voltage drops that the current will go up in order to maintain a 4KW load.

I suspect that at best we can hold the operating load resistance constant, in this case about 14.5 Ohms. If the voltage were to sag to 235 as you suggest than current will go down to 16.2 Amps. Clearly we can not treat a heating element as constant resistance as it is non-linear and has in rush current to boot.

Perhaps for design purposes one does assume that 4KW is the constant, either way, I think the OP is fine as you suggested.

 

[Labradorian]

This is a case where the technical numbers of the code are close but aren't an issue for when the manufactures set the amp/circuit size for their heaters. If you look at a portable 4000W 240V heater, it most likely comes with a 20A 240V cord and plug on it.

yes you are right. I often juggle between the technical numbers and manufacturer ratings. 20A if fine.

cheers

 

[Labradorian]

I am not sure we can consider this heater as a constant power load, and hold 4KW constant, and assume as voltage drops that the current will go up in order to maintain a 4KW load.

I suspect that at best we can hold the operating load resistance constant, in this case about 14.5 Ohms. If the voltage were to sag to 235 as you suggest than current will go down to 16.2 Amps. Clearly we can not treat a heating element as constant resistance as it is non-linear and has in rush current to boot.

Perhaps for design purposes one does assume that 4KW is the constant, either way, I think the OP is fine as you suggested.

yes he's fine.

 

[zmaxmotorsports]

I've been asking some questions in another thread, but wanted to start fresh as I think I may have other issues. Tell me what I have done wrong

2000w and 2500w heaters in my garage hooked up to my panel with 12/2 wire and a 30amp dbl pole breaker.

I have been told that the 30amp breaker is too high for 12/2 wire. And that 4500w on a single circuit is too much.

Solution? Replace the 2500w heater with a 2000w heater and replace the 30amp breaker with a 20 amp breaker?

You could run both of them on a 25a 2pole breaker with 10g wire,figuring 125% load to allow for a little breathing room still gives you only 23 amps and some change.
Or you could just run a separate circuit with some 12/2 and split them up that way,you could get buy with 15a circuits for each.The 12/2 just gives you room to add more later .

 

[zmaxmotorsports]

Yes. 4000W is the absolute max you can put on #12 @ 240V.

4500w at 240v is 18a and change,if you figure it at 125% like a motor load you get 23a and change.