Hi, I am installing a new 125 Amp sub panel 65 feet away from a new 200 amp service. The sub is located in the same shop as the main panel. Do i need to pull a separate grounding conductor for the sub or can the EMT between the main and the sub be used for the grounding bond? I ask as i would like to use 1-1/4 EMT which will only allow three #1 copper conductors. (per conduit fill table 3B) Thus allowing 2-#1 lines and a common max. If i have to pull a separate #6 ground i would have to step up to the 1-1/2 EMT. Basically i wish to know if on a sub panel situation such as this is it allowed to use the EMT conduit as the ground rather than a separate conductor?
BTW - Appendix C, pg. 585 does say 4 #1 are allowed in 1-1/4" EMT; however if you do the arithmetic from Table 4 & Table 5 (EMT usable space & area of THHN tables)you cannot use 4 #1s in 1-1/4" EMT.
However, even though you are allowed to use the EMT as the EGC, I highly recommend you do pull the #6 (the arithmetic works) as your EGC - don't trust the EMT connection over the years to be maintained and work when needed in the event of a fault.
Re: sub panel feeder wire sizes......#7155 02/05/0211:03 PM02/05/0211:03 PM
I have to agree with Dana, don't trust conduits to carry the ground as the years progress...I've already seen far too many lost grounds from installations 15 to 30 years old. Go ahead and pull it, you won't regret it later.