Bonding Service Panels in a Two Family Dwelling

[goldsborough]

At this Two Family Dwelling, I have a 3 Gang Service Meter feeding a House Panel, 1st Floor Apartment, and 2nd Floor Apartment. The size of the incoming SE Cable is 4/0 Aluminum. The load side of the Service Meter Stack is three Number 2 Aluminum SE cables feeding three separate 100 ampere service panels. The contractor used No 6 Copper Bonding Jumper to each service Panel and then in the basement service panel, he used Number 4 AWG to the water pipe. My question is should he have used a Number 4 bonding jumper or is Number 6 legal since each panel is fed with No 2 Aluminum SE cable.

Thank you

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[Tulsa Electrician]

First question.
It water line being used as a electrode.
Second question.
Does the water line serve both units.
Third question.
Does all these service conductor run on the out side and then enter at each level.
Forth question.
New or existing install.

 

[goldsborough]

Water serves both units and is the grounding electrode.
SE Cable to second floor unit outside then nearest point of entrance
SE Cable to neatest point of entrance in basement to House Panel and First Floor Unit. New construction. No common area, House Panel is for outdoor lights and outdoor security cameras.

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[augie47]

Since the water is a grounding electrode it must have the grounding electrode conductor connected within the 1st 5 ft.
250.64(D) requires the grounding electrode conductor originate from a common point ahead of the disconnects (such as the meter enclosure) or from each disconnect.
If you don't come from a common point you can chose to run individual conductors from each disconnect to the electrode(s) or you can run a properly sized common electrode conductor to a point & tap the individual GECs to it.

Mike's pictures in the next slide demonstrate acceptable methods.

 

[augie47]

 

[jaggedben]

A 6awg GEC tap to each panel is fine, but in general the diagram does not show an NEC approved method of grounding the service. As augie referred to, see 250.64(D).

The NEC would be fine with a single 4awg GEC to the neutral bar in the meter bank. The utility might not be.

 

[goldsborough]

Appreciate all of the feedback. So bonding each 100 ampere service panel (neutral terminal bar) with No 6 AWG is fine. 2 Ground rods six feet apart with No 6 AWG. No 4 AWG out of one of the bonded 100 ampere service panels to 5 feet of the water pipe entrance (grounding electrode) is correct.

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[augie47]

IMO, a singe conductor to the water pipe (sized by the overall service conductors) would need taps to each disconnect unless it is connected prior to the disconnects.

 

[jaggedben]

Appreciate all of the feedback. So bonding each 100 ampere service panel (neutral terminal bar) with No 6 AWG is fine. 2 Ground rods six feet apart with No 6 AWG. No 4 AWG out of one of the bonded 100 ampere service panels to 5 feet of the water pipe entrance (grounding electrode) is correct.

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No.

Bonding the neutral isn't the same as grounding. The grounding is supposed to be connected to all the panels, or a point ahead of them. That applies to ground rods and water pipe.

Rea 250.64(D).