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sub panel feeder wire sizes...... #7146 01/24/02 05:23 PM
Joined: Dec 2001
Posts: 5
D
duanet Offline OP
Junior Member
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?

thanks

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Re: sub panel feeder wire sizes...... #7147 01/24/02 06:22 PM
Joined: Jan 2002
Posts: 163
D
dana1028 Offline
Member
I'm now looking at Appendix C of the 1999 NEC, pg. 585 - THHN #1...4 conductors (#1 size) are allowed in 1-1/4" EMT

Re: sub panel feeder wire sizes...... #7148 01/24/02 06:28 PM
Joined: Dec 2001
Posts: 5
D
duanet Offline OP
Junior Member
You may want to check again as my NEC book Table 3B (maximum # of conductors in trade sizes of conduit or tubing) states that a maximum of 3 #1 THHN in 1-1/4

Re: sub panel feeder wire sizes...... #7149 01/24/02 06:48 PM
Joined: Jan 2001
Posts: 1,044
Tom Offline
Member
Where the heck is table 3B?

Table C1 on page 585 is the correct one to use & as dana1028 pointed out 1 1/4" emt is good for 4 #1's.

You don't usually need to pull in the equipment ground, but many electricians prefer to include one in all their conduit work.


Few things are harder to put up with than the annoyance of a good example.
Re: sub panel feeder wire sizes...... #7150 01/24/02 06:51 PM
Joined: Dec 2001
Posts: 5
D
duanet Offline OP
Junior Member
Table 3B is in chapter 9 (tables and examples) page 750 of 1990 NEC

Re: sub panel feeder wire sizes...... #7151 01/24/02 09:54 PM
A
Anonymous
Unregistered
duanet,

Its time to invest in a new NEC book.

Re: sub panel feeder wire sizes...... #7152 01/24/02 11:37 PM
Joined: Jan 2002
Posts: 22
E
eman1963 Offline
Member
i would use the 1 1/4 emt as the ground and run only 3 conductors

Re: sub panel feeder wire sizes...... #7153 01/24/02 11:38 PM
Joined: Mar 2001
Posts: 2,056
R
Redsy Offline
Member
What size breaker are you installing ?

Re: sub panel feeder wire sizes...... #7154 01/25/02 07:56 PM
Joined: Jan 2002
Posts: 163
D
dana1028 Offline
Member
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 02/06/02 12:03 AM
Joined: Feb 2002
Posts: 36
3
3rd degree Burns Offline
Member
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.


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