Hi Everyone,

I have seen all the rules about conduit sizing and the # of conductors allowed but I have not been able to locate
guidelines on when conduit is needed. I am rewiring my
house from scratch and will be installing a 100amp sub-panel.
The supply for the sub-panel will run through the attic. Do I
need to use conduit? Does it matter if it is EMT or plastic/PVC?

Thanks,

Victor

 

Certain areas like Chicago require conduit. Other times it is only required as physical protection for a cable.

Can you describe how you will get from the panel to the new sub-panel? The cable would need protection if installed within 7' of the attic scuttle.

 

You do not have to use conduit, you may use a service entrance cable of sufficient size. You may not run single wires without conduit.

If you use conduit, I would recommend EMT. PVC emits very toxic fumes when it burns. We all hope that never happens to your house, but it's safer to use EMT in that unfortunate possibility.

 

Thanks for the feedback. I can make sure that the cable is more than 7' away from the attic scuttle. I will use a cable with all 3 wires. Am I supposed to use a 4th wire to ground the
2 panels together? Usually the metal conduit would provide
the connection.

 

Cable should not be use in conduit except for short pieces of conduit for protection. You should use individual wires in a continuous conduit run. If cable is used the ground wire should be a part of the cable.

 

The big mistake that is most commonly made in sub panels is mixing of the ground and neutral because the panel bonding jumper is not removed. Many panels come with the main bonding jumper as a screw from the neutral bar to the case of the panel, bonding neutral and ground. For sub panels, this must be removed and neutral must stay completely isolated from ground. Only in the main panel should they be bonded.

As Ray said, the ground wire from the main to sub should be included in the cable, if you use cable. If you use metal conduit (no flex unless it's under 6'), that would be your ground path and a fourth wire would be unnecessary (unless it was a very short flex run, then you DO need the ground wire).

Rich

 

OK. I think I understand. The total run is approximately 50'. I will use a cable that has 4 wires and no conduit. I will make sure that the ground and neutral are not connected to each other in the sub-panel.

Thanks Everyone! I am sure this is not the last time you will hear from me......

Victor