main bonding question.

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stew

Senior Member
Had a panel replacement recently where the 325 meter base was located on a detached garage. There was a 200 amp 120/240 service panel in the garage with only a few 240 volt circuits for welders and a couple of lighting and branch circuit loads. This panel had a main bonding #4 cu going back to the meter enclosure. The 120/240 to the house was run in triplex direct burial cable in a rigid steel stub and apparently then run under the wide garage slab underground to the house to the crawl space where a connection was made(properly spliced) and the run in another rigid steel stub up thru the plate to the 200 amp house service panel. There was a # 4 cu solid run from the house panel thru the stub with the service conductors and then back to the meter base. I dont know how this ever passed even 30 years ago. There was no main bonding conductor from the house panel to the water piping system. I installed that conductor at the house and bonded all the piping. Question is should I remove the redundant bonding back to the meter base or is it ok to leave it. BTW the neutral is bonded at the meter base. Kind of confused me. They had bonded the piping system with a # 6 solid cu in the crawl with 2 sets of bonding clamps and 2 separate #6 solid cu also running back underground some where which I assume was a grounding electrode system somewhere however no connectiion was made back to the house service panel either. I ran a new grounding electrode system from the panel with 2 rods . Very weird system originally in my opinion. Remove old or leave it?
 

david

Senior Member
Location
Pennsylvania
Looking at 230.40 exception No. 3 the triplex going from the meter to the garage is compliant
Also using that same exception the triplex going from the meter to the detached house is compliant.

The # 4 bonding from the meter to the garage service panel would create a unwanted path for current and you should consider removing it. AT the garage you do need to establish a grounding electrode system a # 6 to ground rods would meet the codes requirement for that location. That electrode connection at the service panel or from the meter enclosure would be compliant.

There is no requirement that the bonding at the detached house to the water system had to be at the service panel you pointed out that the water system was bonded in the crawl space at the detached house that location would have been compliant. (the bond should have been a #4)
You also pointed out that there are two # 6 bonds going some- where from the water pipe. (most likely to ground rods) also compliant

You pointed out that there was also a # 4 going from the detached house to the meter enclosure. I agree with your assessment that it creates a parallel path and should be removed.

The splice from the URD at the house did it transition to another wiring insulation type or did it just extend the length of the URD? They may have not wanted to take the URD into the house that could explain the splice in the crawl space.
The length of the service entrance conductors entering the detached dwelling was a judgment call from the authority at the time of the original inspection
 
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augie47

Moderator
Staff member
Location
Tennessee
Occupation
State Electrical Inspector (Retired)
As with most discussions here, the devil is in the details.
As far as the garage is concerned, I agree with david in that you need to establish a grounding electrode system there connected to the grounded conductor per 250.250.23(A)(1).
If the neutral is bonded in the garage panel, then in all probability your #4 is establishing a parallel path. If the neutral is not bonded to the panel, your #4 may be acceptable depend on how iot is terminated at each end.
The same holds true for the house panel. The #4 and the neutral would only be creating a parallel path if they are both connected to the same point at each end.
Most inspectors would probably want a service disconnect at the house prior to the panel, but as pointed out, the distance the conductors run unprotected inside the house is a judgement call.
I would probably assure there was a grounding electrode system at each structure, connect them the the neutral at the panels and eliminate the #4 while bonding the neutrals.
 

stew

Senior Member
actually David all they did was bond the pipes together and run 2 # 6 cu out to I guess a couple of ground rods which are not now evident. The #4 cu was never brought to the water pipes. It just was landed in the panel,run out back to the meter bas and landed there. So no bonding done from the panel to water until I did it!. I think I will unland the original 4 cu as I also think this is an oblectionable extra path. does not need to be there and was actually serving no function except as a parallel neutral path with and extra # 4cu. Someone really didnt know what they were doing here. I have a feeling this was done just prior to when inspections took place in this area and was done by the homeowner/builder. Also the grounding electrode system that was there was never brought to the panel either. Just from the pipe bonds out to the rods! not so effective eh? lol
 
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