Smaller wire after a junction box

[gbarker121]

I hope this isn't aleady covered somewhere. I searched but couldn't quite find what I was looking for.

I have a crowded subpanel with room for one more 2 pole circuit breaker. I want to install two 240v 3200watt Infrared heaters.

My thought is to run 8/3 from a single 40Amp CB to a junction box and then run 2 seperate 12/3 "sub-runs". One to each of the variable heat controllers included with each heater and then to each heater.

Can I do that? Run smaller wire from the junction box, in flex directly to the controller and then to the heater? What I have found makes me think that I'd have to put 20Amp CB at each "sub-run" to make this right but thought I'd ask.

Cheers,
G

 

[pattenp]

You can't run the #12 directly off of the #8 that is protected @40A. #12 is 20A, so you'd have to do a sub-panel with 20A breakers for the 2 #12 circuits. Also for 240V you only need 2 conductors w/ground which would be 8/2 or 12/2.

 

[pentavolvo]

cant do it without a small subpanel with 20 amp breakers in it

 

[sberry]

I think maybe you can. I believe a range top and oven are wired similar?

 

[Gooch]

I think maybe you can. I believe a range top and oven are wired similar?

it's doable.

210.19(A)(4) Exception No.1 (d)

 

[Aceman]

No you can't do that.

See if your panel will accept a 20/20 quad. That'll give you two 240v circuits in 2 panel spaces.

 

[Gooch]

No you can't do that.

See if your panel will accept a 20/20 quad. That'll give you two 240v circuits in 2 panel spaces.

does the section i listed not specifically allow it?

 

[pattenp]

does the section i listed not specifically allow it?

No because 210.19 section pertains to the proper wire size to the loads served. Plus I don't think those would be considered tap conductors. The over current protection is what limits it to 20A for #12, 240.4

 

[Aceman]

does the section i listed not specifically allow it?

The section you posted allows taps for "infrared lamp industrial heating appliances." I couldn't tell you if they are referring to the heater as "industrial" or the environment it is in.

But, my opinion is they are referring the environment as industrial rather than the fixture, which means his home wouldn't fall under the exception.

He would also have to comply with the tap rules of article 240.

For the record, I have tapped infrared heaters like the OP has mentioned, but never in a residence, only in an industrial setting.

I think a straight forward 20 amp breaker with 20 amp wire is a lot more clear cut way to go in a residence myself.

EDIT: The more I think about it the more I'm on the fence. I don't know if I'm reading too much into industrial or not?

 

[danielzig]

Maybe you could put a 60 amp double pole breaker or even a 100 amp double pole to a new sub panel with not only room for your 2x20 amp feeds you require, but also some room for additional loads in the future.

 

[Gooch]

The section you posted allows taps for "infrared lamp industrial heating appliances." I couldn't tell you if they are referring to the heater as "industrial" or the environment it is in.

But, my opinion is they are referring the environment as industrial rather than the fixture, which means his home wouldn't fall under the exception.

He would also have to comply with the tap rules of article 240.

For the record, I have tapped infrared heaters like the OP has mentioned, but never in a residence, only in an industrial setting.

I think a straight forward 20 amp breaker with 20 amp wire is a lot more clear cut way to go in a residence myself.

EDIT: The more I think about it the more I'm on the fence. I don't know if I'm reading too much into industrial or not?

240.21(A) sends you right back to 210.

Also read the definition of 'Tap Conductors' 240.2

I assumed since I'm on a Garage forum that it wasn't for the dwelling, but if it is, I agree, it is not acceptable.

 

[Charles (in GA)]

it's doable.
210.19(A)(4) Exception No.1 (d)

No you can't do that.
See if your panel will accept a 20/20 quad. That'll give you two 240v circuits in 2 panel spaces.

does the section i listed not specifically allow it?

The real reason it doesn't apply is this is dealing with resistance heating equipment. Electric heating is considered a continuous load, and 210(A)(1) specifically applies here, requiring the conductors to have a minimum capacity of 125% of the continuous load.

Edit: I missed the IR heat part of the OP till now, but I think this still applies.

Charles

 

[gbarker121]

You can't run the #12 directly off of the #8 that is protected @40A. #12 is 20A, so you'd have to do a sub-panel with 20A breakers for the 2 #12 circuits. Also for 240V you only need 2 conductors w/ground which would be 8/2 or 12/2.

No you can't do that.

See if your panel will accept a 20/20 quad. That'll give you two 240v circuits in 2 panel spaces.

You guys are awsome.

I had been thinking of these as taps but wasn't sure if I had the right context. I'm much smarter now.

After posting, I came to think that I'd need to do what pattenp (and others) proposed which would have worked but been a drag. However, the winner of this conversation is Aceman with the quad recommendation. I didn't know such a thing existed and it's going to fill in all the gaps.

Thanks!

A follow on question:

Also for 240V you only need 2 conductors w/ground which would be 8/2 or 12/2.

Confuses the hell out of me. I've wired some 240v outlets (on a different circuit) with 8/3 (Home Despot recommended - <hangs head>). I was going to use the 2 hots and common for the socket and the ground to bond the box... Not necessary? When is a dedicated common required (if that's not too broad a question).

Thanks again for the help!

G

 

[MrMark]

Might have been a dual voltage device like a range?

There is no "common" (the correct term is neutral or grounded conductor or WHITE) on a 240V circuit. The neutral is only to give you 120V

 

[pattenp]

If the device is only 240V then you need 2 hots and a ground. If the device needs 240V plus 120V then you need 2 hots, 1 neutral, and a ground. Either hot leg to the neutral gives you 120V.

 

[gbarker121]

If the device is only 240V then you need 2 hots and a ground. If the device needs 240V plus 120V then you need 2 hots, 1 neutral, and a ground. Either hot leg to the neutral gives you 120V.

Might have been a dual voltage device like a range?

There is no "common" (the correct term is neutral or grounded conductor or WHITE) on a 240V circuit. The neutral is only to give you 120V

Ah! So (most typically) the only time you really need 4 wires is between service panels that might be called on to provide both 120 and 240v branch circuits or when running to devices that need both 120 and 240 (like maybe some contraption with a 240v contactor controlled by 120v?).

Last question then. Like I said, I've already pulled 8/3NM to a few junction boxes and then used short tap conductors to connect outlets. Can I just remove the white wire from the 8/3 tap conductors and leave it in place for the main run in case I need 120 off that circuit somewhere down the road?