12-4 240v/240v

[1.21 Gigawatts]

I have an interesting question ( i think).

I found a couple splice boxes in basement ceiling that works some electric heaters on 1st floor.
Feed comes in Splice box #1 and out on the black & white 240v) of the 12-4 to splice box #2. From there up to the thermostat. then a black & white from the thermostat to Splice Box #2 which splices through with the Red & Blue on the 12-4 and back to Splice box #1. From there to the heater upstairs.

Question is... can you have a 240v feed AND 240v return in this 12-4 bx armor? Wouldnt heat be an issue inside it?

Thanks.

 

[infinity]

Not a problem although it would count as 4 CCC's.

 

[kwired]

Agree with infinity, 4 CCC's would need a .80 adjustment factor, but your conductors are likely 90C so you start that adjustment from 90C ampacity table, which is 30 amps leaves you with ampacity of 24 amps in that cable.

 

[1.21 Gigawatts]

Interesting guys. Thanks..

Here's a pic and closeup. 4 wire Middle knockout. MC?

 

[1.21 Gigawatts]

Not a problem although it would count as 4 CCC's.

And thats what made me bring this up.. if we're limited to filling up a conduit how can we have 4 CCC's in this little armored cable.

I also think the 2 pole 20 breaker would trip from overheating before the risk of a fire since its armored cable but im just going to run a new 12-2 for the return.

 

[infinity]

And thats what made me bring this up.. if we're limited to filling up a conduit how can we have 4 CCC's in this little armored cable.

I also think the 2 pole 20 breaker would trip from overheating before the risk of a fire since its armored cable but im just going to run a new 12-2 for the return.

4 CCC's in a 12/4 cable with 90° C conductors is not a problem on 20 amp circuits.

 

[bwat]

And thats what made me bring this up.. if we're limited to filling up a conduit how can we have 4 CCC's in this little armored cable.

I also think the 2 pole 20 breaker would trip from overheating before the risk of a fire since its armored cable but im just going to run a new 12-2 for the return.

You can certainly do what you want. But like the others said, 4 CCC's is no problem. You just need to de-rate. It almost sounds like you're mixing conduit fill restrictions with de-rating factors based on CCCs in a raceway. Maybe not.

 

[mbrooke]

You could just switch one leg and put a lock provision on the breaker. But that would be me in new work. In this case as others have said there is no issue as is.

 

[kwired]

And thats what made me bring this up.. if we're limited to filling up a conduit how can we have 4 CCC's in this little armored cable.

I also think the 2 pole 20 breaker would trip from overheating before the risk of a fire since its armored cable but im just going to run a new 12-2 for the return.

Presuming your cable has 90C conductors, you derate them from 30 amps to 24 amps, still enough that a 20 amp OCPD is fine here. Does not matter if they are in 1/2 raceway, 4 inch raceway or that tight fitting cable sheath, it is still four current carrying conductors and ampacity is the same for all those situations I mentioned.