I’m new to This trade (HVAC/R TECH). I need to clarify an arguement I had today with a friend (non electrician). Do Sub panel boxes need to to be bonded to the service box via metal conduit? I said yes. I looked it up in the NEC (1999 BOOK)
QUOTE FROM THE BOOK "To remove dangerous voltage,we must clear the ground-fault by quickly opening the circuit overcurrent protection device.
To open the circuitovercurrent protectiondevice,the saftey grounding path must have sufficient low impedance.
This is accomplished by bonding metal parts to each other then bonding metal parts to the grounded (neutral)conductor at one location in accordance with sec 250-142"
Then he asked about plastic conduit that electricians are using. Well now I’m LOST AGAIN.
Plus I have an elecrtical book for wiring houses from Menards and they do not talk about bonding sub panels (Black &Decker complete guide to home wiring). So am I right about bonding sub panels with metal conduit, and what about plastic conduit?
When using EMT which I will take as such in your example, you are allowed to use the conduit itself as the Equipment Grounding Conductor ( which I happen to wish they would rename it as Equipment Bonding Conductor…but alas I don’t sit on the CODE panel…YET anyway…
SO bacically you have to ensure the BONDING remains in place when using that conduit to ensure a low impedence path for a fault…when using non- metalic rigid conduit ( PVC-40 or 80 ) you will have to ensure a EGC is run ( EGC -ie: Equipment Grounding(BONDING) Conductor from the panel through that conduit to the device…
If using Romex or ( Non-Metalic Sheath Cable ) the EGC will be within the cable itself ( thus in older applications with NO EGC thus ungrounded ) and that is your bonding conductor.
I think THIS is where people get confused with the NEC…the NEC itself does not seem to know when something is a BONDING conductor and when it is a GROUNDING conductor…yet they TRY to define it and they do it WRONG…yep I said it…the NEC Code Panel is doing it WRONG in my opinion but again who am I…country boy in VA…
