I have a 120/240 volt, 200 amp main, single phase, feed through load center outside a single family dwelling unit as the main disconnect. Several 120 and 240 volt loads are derived from this load center. The grounding electrode system consists of #4 solid bare copper to three ground rods and the cold water system. The neutral bar is bonded to the enclosure at this location. A #4/0 AL SE cable is connected to the feed through lugs on the bus bars feeding another 120/240 volt, 200 amp, main lugs only, single phase load center inside the dwelling unit. Several 120 and 240 volt loads are derived from the inside load center. The neutral bar is bonded to the enclosure at this location also, but is not bonded to the cold water system or the grounding electrode system. I have not found this exact situation in article 250 of the handbook and am looking for the correct way to ground and bond the inside load center. Closest situation I found was article 250.32, Two or More Building or Structures Supplied from a Common Service. Can I just run another #4 solid bare copper grounding electrode conductor to the existing grounding electrodes?
Grounding/Bonding A Load Center Fed Out Of A Feed Throug
- Thread starter floyd
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sandsnow
Senior Member
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- Southern California
Re: Grounding/Bonding A Load Center Fed Out Of A Feed Throug
When you say outside the dwelling, I assume mounted on the wall outside. 250.32 does not apply as the panels are in the same building.
The first panel is the service. The second panel is a sub-panel. The SE between them is a feeder. A feeder requires an equipment grounding conductor. So it need to be SER type. The neutral in the second panel shall not be grounded.
see 250.24(A)(5); 250.102; 250.142
When you say outside the dwelling, I assume mounted on the wall outside. 250.32 does not apply as the panels are in the same building.
The first panel is the service. The second panel is a sub-panel. The SE between them is a feeder. A feeder requires an equipment grounding conductor. So it need to be SER type. The neutral in the second panel shall not be grounded.
see 250.24(A)(5); 250.102; 250.142
bphgravity
Senior Member
- Location
- Florida
Re: Grounding/Bonding A Load Center Fed Out Of A Feed Throug
Why so many ground rods?
The neutral in the second panel already is grounded. Thats what it is, the grounded conductor. You shouldn't have this conductor bonded to the enclosure and the equipment grounding conductors from the branch circuits should not be connected to it either. An equipment grounding bar should be installed to the second enclosure for all equipment grounds.
Re: Grounding/Bonding A Load Center Fed Out Of A Feed Throug
Thanks for the help. Just needed some second opinions. What threw me was the subpanel was fed straight off of the bus bars and not from a separate breaker. Dwelling was built in 1994 and if my short memory serves me right this installation was to code at the time. I will install grounding bars in subpanel and re-feed with SE-R. I could not find SE-R cable in the 2002 or 2005 code book. Where is it in the code book? Do they make a #2/0 CU SE-R? I installed the three ground rods in a triangle to decrease resistance in the grounding electrode system. I had a hum in my home theater system and found system was plugged into more than one outlet that were not on the same phase.
Thanks for the help. Just needed some second opinions. What threw me was the subpanel was fed straight off of the bus bars and not from a separate breaker. Dwelling was built in 1994 and if my short memory serves me right this installation was to code at the time. I will install grounding bars in subpanel and re-feed with SE-R. I could not find SE-R cable in the 2002 or 2005 code book. Where is it in the code book? Do they make a #2/0 CU SE-R? I installed the three ground rods in a triangle to decrease resistance in the grounding electrode system. I had a hum in my home theater system and found system was plugged into more than one outlet that were not on the same phase.
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