detached garage grounding,bonding

[boyle78]

Here is what I have.
A residence with a 200a drop at the house and what will be a 200a drop at the garage. Two seperate meters. The water main and meter is in the house, but now the water line will be tapped into for supply of the garage. H.O. wants a light on the garage to be 3wayed from the house also. My question and concern is that since the water pipe and a switched load is shared between the two structures, do I simply pound my two ground rods and bond my water pipe in the garage main panel? Overthinking might be my case in this one. I guess this would be like two seperate services at two seperate houses,,,,,but with a common light shared between the two homes?

 

[augie47]

I think it's an excellent question.
1st point concerns a branch circuit from one biding routed to another and if that is allowable (I know of no prohibiting Code section but I may soon learn ), would you tie the grounds together.
My feeling is that you would not want the structure grounds interconnected as you would set up a current path that might be undesirable.
I hope an inter sting discussion follows.

 

[boyle78]

Something didn't seem right....so I put the situation and question out there!

 

[mpd]

I think it's an excellent question.
1st point concerns a branch circuit from one biding routed to another and if that is allowable (I know of no prohibiting Code section but I may soon learn ),.

I was thinking the same thing, i was thinking maybe 225.30 but not so sure

 

[augie47]

I was thinking the same thing, i was thinking maybe 225.30 but not so sure

That was my first thought also, but there is no mention of services there.

 

[hurk27]

I think it's an excellent question.
1st point concerns a branch circuit from one biding routed to another and if that is allowable (I know of no prohibiting Code section but I may soon learn ), would you tie the grounds together.
My feeling is that you would not want the structure grounds interconnected as you would set up a current path that might be undesirable.
I hope an inter sting discussion follows.

Why would this be any differant from two houses on the same transformer that share the same city water main very common here.

As far as the 3-way light goes, 225.30(D) allowes such

for different uses, such as control of outside lighting from multiple locations.

 

[Buck Parrish]

IMO , A x-10 or RF switch would be a better fit versus the 3 way wiring.

 

[Smart $]

The 3-way lighting circuit isn't a problem... just keep the branch circuit egc isolated from the other building's.

The shared water line electrode is debatable, as to causing objectionable current (i.e shared neutral and ground-fault current paths... but as you said, this is no different than a services to each of two or more houses connected to the same metallic water main.

 

[boyle78]

IMO , A x-10 or RF switch would be a better fit versus the 3 way wiring.

googleing now....

 

[mpd]

That was my first thought also, but there is no mention of services there.

yeah i was reaching, i was even thinking 210.25 (A) but don't think that will work either in this case

 

[hurk27]

googleing now....

Check out www.smarthome.com

Better yet http://www.smarthome.com/_/Dimmers_Lighting_Appliance_Control/Leviton/_/z/1j1/nav.aspx

Call them and just tell them what you want to do and if you want dimming or not.

 

[hurk27]

That was my first thought also, but there is no mention of services there.

And you will not find none, or will you find anything in 230 that prevents a branch circuit from one building to another.

 

[augie47]

Why would this be any differant from two houses on the same transformer that share the same city water main very common here.

..............................

would not be any different...which is my point...
I would't want the #14 or #12 EGC trying to carry current between the two services.
I can see structure one loosing a neutral and that branch trying to carry the load.

 

[hurk27]

yeah i was reaching, i was even thinking 210.25 (A) but don't think that will work either in this case

225.30 covers feeders and or branch circuit from one building to another, or does it disallow it when the buildings are fed by there own service, a utility might say something because of the ability of combining the same phase from each service which could cause meter error readings, but the NEC is silent, if it was not allowed what would be the purpose of the requirments in 225.37? which by the way must be followed when doing this.

 

[hurk27]

would not be any different...which is my point...
I would't want the #14 or #12 EGC trying to carry current between the two services.
I can see structure one loosing a neutral and that branch trying to carry the load.

Why would the EGC's be connected to the garages EGC's? good point, I would keep them isolated from each other, but we have the same problem with a house and the cable's shield bonded at the pole and at the house, same thing happens when the neutral is lost, but done every day.

 

[curt swartz]

I have not spent anytime studying this so I'm just throwing this out there. Both article 225 and 230 limit the number of supplies to a building to one with some exceptions. One of the exceptions in 225 allows additional supplies for "lighting control". I don't believe article 230 has an exception to allow this. If this is the case what allows the lighting control wiring between 2 buildings supplied by two services?

 

[hurk27]

I have not spent anytime studying this so I'm just throwing this out there. Both article 225 and 230 limit the number of supplies to a building to one with some exceptions. One of the exceptions in 225 allows additional supplies for "lighting control". I don't believe article 230 has an exception to allow this. If this is the case what allows the lighting control wiring between 2 buildings supplied by two services?

230 does not have any disallowments for any other branch circuit feeds, and the requirment of 225.37 clearly seems to say this is done or there wouldnt be a 225.37

Where a building or structure has any combination of feeders, branch circuits, or services passing through it or supplying it

 

[mpd]

225.30 covers feeders and or branch circuit from one building to another, or does it disallow it when the buildings are fed by there own service, a utility might say something because of the ability of combining the same phase from each service which could cause meter error readings, but the NEC is silent, if it was not allowed what would be the purpose of the requirments in 225.37? which by the way must be followed when doing this.

i agree

 

[kwired]

Why would this be any differant from two houses on the same transformer that share the same city water main very common here.

As far as the 3-way light goes, 225.30(D) allowes such

225.30 applies to buildings supplied by same service. I don't think you can bring a circuit supplied by another service to a building like that.

Suggestion is to use X-10, RF, or low voltage controls between the two buildings.

Add: I posted this before reading second page of posts, I see others feel much same way. I don't see that you can't do this but would discourage doing so. Still would rather see x-10, RF or low voltage control.

 

[Smart $]

225.30 applies to buildings supplied by same service. I don't think you can bring a circuit supplied by another service to a building like that.

Suggestion is to use X-10, RF, or low voltage controls between the two buildings.

Add: I posted this before reading second page of posts, I see others feel much same way. I don't see that you can't do this but would discourage doing so. Still would rather see x-10, RF or low voltage control.

The garage-light branch circuit is only switched at the house. It does not serve the house (i.e. no loads of the house are powered by this circuit). Hence, 225.30 does not apply.