300.20 Question

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ceb58

ceb58

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Raeford, NC
I was called to look at an existing installation to see what it would take to correct several problems. The main one was a 200 amp main breaker panel that was recessed into a cinderblock wall. There were 4 3/4" EMT conduits that came out of the wall about 3" above floor level. Someone had installed a junction box over the 4 conduits and left the box with a 1 1/2" conduit exposed on the wall to a sub panel. Here is where it gets funny in the 3/4" conduit they ran a single #3 in each one of the 3 conduits (2 hot 1 Net.) and in the 4th conduit was a #8 EGC. The distance from the panel to this J box is less than 3 ft where they bring all the conductors back together in the one conduit. But it got me thinking, I know it is a violation of 300.3 (B) and 300.20 but would there be a real world problem if it were left this way or could it build up too much heat from induction?
 
ceb58 said:
I was called to look at an existing installation to see what it would take to correct several problems. The main one was a 200 amp main breaker panel that was recessed into a cinderblock wall. There were 4 3/4" EMT conduits that came out of the wall about 3" above floor level. Someone had installed a junction box over the 4 conduits and left the box with a 1 1/2" conduit exposed on the wall to a sub panel. Here is where it gets funny in the 3/4" conduit they ran a single #3 in each one of the 3 conduits (2 hot 1 Net.) and in the 4th conduit was a #8 EGC. The distance from the panel to this J box is less than 3 ft where they bring all the conductors back together in the one conduit. But it got me thinking, I know it is a violation of 300.3 (B) and 300.20 but would there be a real world problem if it were left this way or could it build up too much heat from induction?
Click to expand...

Just when you think ya have seen it all! Things like this always amaze me.
 
Depends on the load. The magnetic fields don't cancell and this installation will have inductive heating.
Can you post a picture?
 
tom baker said:
Depends on the load. The magnetic fields don't cancell and this installation will have inductive heating.
Can you post a picture?
Click to expand...
Will try if I go back. Gave them a price to cut wall and correct problem but its a "been work'en like that for years" situation :happysad:
 
My understanding is that the inductive heating from this type of installation is not a real big problem at that amount of current.
 
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