I am replacing a 3000 amp lateral to an overhead. Will be installing a 3000 amp breaker outside, which will make this my new service entrance and the existing 3000amp, a feeder. Will size ground per 250.122(400MCM) From my understanding for the 8 parallel feeders metal conduit (3-500MCM) This will need to be in each conduit (250.122F1). And since this is in a raceway and not multiconductor cable the ground fault on this breaker will not apply to reduce the size (250.122F2)To not have to upsize my 3" conduit for this size of ground I am going to use the conduit as equipment ground. Are there any exceptions or any other sections that would allow sizing this smaller?
Equipment Grounding conductor
- Thread starter gbd
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Re: Equipment Grounding conductor
Thanks for the reply, you are correct in that there will be a grounded conductor. Usually I will install EGC in all conduits but being the size of this one I am opting out. Another ques. maybe I could use some input on for my grounded conductor I am wanting to use a 1/0. My reference I am using is 250.24 B.1. taking 12.5% from 500mcm (Chapt. 9 table 8) after calculations I could use a #2 but this section limits me to a 1/0. Am I applying this rule correctly? The unbalanced load on this feeder is minimal.
Thanks for the reply, you are correct in that there will be a grounded conductor. Usually I will install EGC in all conduits but being the size of this one I am opting out. Another ques. maybe I could use some input on for my grounded conductor I am wanting to use a 1/0. My reference I am using is 250.24 B.1. taking 12.5% from 500mcm (Chapt. 9 table 8) after calculations I could use a #2 but this section limits me to a 1/0. Am I applying this rule correctly? The unbalanced load on this feeder is minimal.
jtester
Senior Member
- Location
- Las Cruces N.M.
Re: Equipment Grounding conductor
gbd
If indeed you are talking about the feeder and not the service, there doesn't have to be a neutral at all, unless you have l-n loads on the feeder. 220.22 is the rule for sizing feeder neutrals. If you install a neutral, you will have parallel conductors and you are stuck with the 1/0 minimum. There is an exception for #2 in existing installations with engineering supervision, 310.4 Exception 4.
Jim T
gbd
If indeed you are talking about the feeder and not the service, there doesn't have to be a neutral at all, unless you have l-n loads on the feeder. 220.22 is the rule for sizing feeder neutrals. If you install a neutral, you will have parallel conductors and you are stuck with the 1/0 minimum. There is an exception for #2 in existing installations with engineering supervision, 310.4 Exception 4.
Jim T
jtester
Senior Member
- Location
- Las Cruces N.M.
Re: Equipment Grounding conductor
dillon3c
Your approach used the cross sectional area of the conductor and insulation. While 250.24 doesn't say it specifically, I believe the correct approach is to use the area of the conducing material only, in this case a 500 kcmil conductor cross sectional area. Their description of the conductors is independent of the insulation type.
Jim T
dillon3c
Your approach used the cross sectional area of the conductor and insulation. While 250.24 doesn't say it specifically, I believe the correct approach is to use the area of the conducing material only, in this case a 500 kcmil conductor cross sectional area. Their description of the conductors is independent of the insulation type.
Jim T
Re: Equipment Grounding conductor
I am actually talking about the service and feeder. With some phase to neutral loads. By replacing the the lateral and installing to an overhead system 310-4 ex. 4 I did not think applied because since I am installing new, that it could not be considered existing. So to some up what I've heard 1/0 needs to be used for Service and based on 220-22, determine max unbalance and size grounded conductor for that value.
I am actually talking about the service and feeder. With some phase to neutral loads. By replacing the the lateral and installing to an overhead system 310-4 ex. 4 I did not think applied because since I am installing new, that it could not be considered existing. So to some up what I've heard 1/0 needs to be used for Service and based on 220-22, determine max unbalance and size grounded conductor for that value.
pierre
Senior Member
- Location
- Westchester County, New York
Re: Equipment Grounding conductor
Read 250.24(B)(2), particularly the last sentence.
Pierre
Read 250.24(B)(2), particularly the last sentence.
Pierre
Re: Equipment Grounding conductor
Yes Mr Belarge,you are correct. My running "mock calculation" as stated, "not a option".250.24(b)(2)covers the minimum size grounded conductor for this installation.But Mr. Belarge Sir,upon running #'bers for one raceway in Parallel:THWN
500mcm=0.7073x3=2.1219
egc 400mcm---------=0.5860
neut.1/0------------=0.1855
---------
2.8934
Yes Mr Belarge,you are correct. My running "mock calculation" as stated, "not a option".250.24(b)(2)covers the minimum size grounded conductor for this installation.But Mr. Belarge Sir,upon running #'bers for one raceway in Parallel:THWN
500mcm=0.7073x3=2.1219
egc 400mcm---------=0.5860
neut.1/0------------=0.1855
---------
2.8934
pierre
Senior Member
- Location
- Westchester County, New York
Re: Equipment Grounding conductor
Whenever someone calls me Mr. Belarge, I get nervous. Either they are looking for money or I did something wrong.
Pierre
Whenever someone calls me Mr. Belarge, I get nervous. Either they are looking for money or I did something wrong.
Pierre
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