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cansley
Panels/disconnects/grounding

Firstly, thanks for any assistance. Situation is as follows: Older home with electric power coming in off above-ground pole. Connection runs from pole to detached garage (meter is on the garage side) then to a disconnect (fairly old I think) with 100A and 60A switches. 60A goes through wall to a small panel in the garage. 100A goes back up to another weatherhead and travels suspended to house (about 30 ft away). Neither meter, disconnect nor garage panel appear to be grounded to earth. In the home there is a 100A panel that is earth ground (8ft copper rod) and bonded to copper plumbing also. Bonding screw is installed and ground and neutral bars are connected. There are only 3 wires (2 hot and neutral) going from garage to house (again, suspended in the air, so no conduit). House panel has a 40A dual pole breaker that feeds a subpanel with only one breaker (also 40A DP) that goes to the A/C unit. My questions concern:

(1) whether the house panel should be treated as a subpanel (i.e. should I separate the ground and neutral bars)

(2) should the main disconnect and/or garage panel be earth grounded also? And

(3) should I remove the A/C subpanel (i.e. is it bad to have the two breakers is a row on a single circuit).

Thanks so much!

JLMCDANIEL
Re: Panels/disconnects/grounding

Not absolutely positive, but I believe the disconnect would be considered a distribution point feeding two separate panels. The panel in the garage should be treated as a main panel and grounded to a ground electrode as well as the panel in the house.

Two breakers for the A/C is redundant, however code requires a shutoff near the unit to cut power during servicing.
Jack

cansley
Re: Panels/disconnects/grounding

Jack,
My gut told me basically the same thing you did. Many thanks for your reply.

Clarence

ZZZ
Re: Panels/disconnects/grounding

The service stops and the feeders begin at the first overcurrent device. The garage panel is the service and should have a ground rod, and the neutral bonded to the ground.
The wire into the house should contain both a neutral and a ground to meet 2008 NEC code, and the neutral would be insulated from the subpanel (the bonding screw or wire is not used). All neutrals in the house sub panel go to the neutral bar. All ground wires would go to the ground bar, along with the ground rod and piping ground.
Since yours is an existing installation, you are allowed to have only three wires feeding the house and bond the ground and neutral at this subpanel. (NEC 250.32 (B) Exception)
It required on new installations that you have both a ground and a neutral feeding a separate building, because if the neutral becomes disconnected, all the unbalanced current it is carrying will be transfered to the grounding system, including appliance frames. It is unlikely to trip the main breaker but will definitely be capable of electrocuting someone.

Re: Panels/disconnects/grounding
cansley wrote:

Firstly, thanks for any assistance. Situation is as follows: Older home with electric power coming in off above-ground pole. Connection runs from pole to detached garage (meter is on the garage side) then to a disconnect (fairly old I think) with 100A and 60A switches. 60A goes through wall to a small panel in the garage. 100A goes back up to another weatherhead and travels suspended to house (about 30 ft away). Neither meter, disconnect nor garage panel appear to be grounded to earth. In the home there is a 100A panel that is earth ground (8ft copper rod) and bonded to copper plumbing also. Bonding screw is installed and ground and neutral bars are connected. There are only 3 wires (2 hot and neutral) going from garage to house (again, suspended in the air, so no conduit). House panel has a 40A dual pole breaker that feeds a subpanel with only one breaker (also 40A DP) that goes to the A/C unit. My questions concern:

(1) whether the house panel should be treated as a subpanel (i.e. should I separate the ground and neutral bars)

(2) should the main disconnect and/or garage panel be earth grounded also? And

(3) should I remove the A/C subpanel (i.e. is it bad to have the two breakers is a row on a single circuit).

Thanks so much!

yes the house panel should be treated as a sub with seperate nuetrals and grounds all the way from the main breaker on the outside of the garage. You need 2 ground rods on the exterior disconnect at the garage. Because the house is a seperate building you either must have an additional rod there or you must NOT depending on the version of the code your state has adopted and is enforceing. Water pipes can then be bonded to any portion of the GEC including the groundbars in a sub panel assuming the entire plumbing system has been made electrically continuous (even when being serviced)by adding bonding jumpers to places like the h/w heater water main water filter well or any random sections of dissimilar metals. Inside the garage and the a/c panel the nuetrals and grounds must be seperated.

Re: Panels/disconnects/grounding
ZZZ wrote:

The service stops and the feeders begin at the first overcurrent device. The garage panel is the service and should have a ground rod, and the neutral bonded to the ground.
The wire into the house should contain both a neutral and a ground to meet 2008 NEC code, and the neutral would be insulated from the subpanel (the bonding screw or wire is not used). All neutrals in the house sub panel go to the neutral bar. All ground wires would go to the ground bar, along with the ground rod and piping ground.
Since yours is an existing installation, you are allowed to have only three wires feeding the house and bond the ground and neutral at this subpanel. (NEC 250.32 (B) Exception)
It required on new installations that you have both a ground and a neutral feeding a separate building, because if the neutral becomes disconnected, all the unbalanced current it is carrying will be transfered to the grounding system, including appliance frames. It is unlikely to trip the main breaker but will definitely be capable of electrocuting someone.

What he said!!
Except the main is the disconnect outside assuming it contains overcurrent protection for the house as well. If the house isnt protected by an overcurrent device at the garage then I think we are both off a little bit. Thats assuming your state is enforcing 08 if there still on 05 the rod location could be a little different, unless again there is no overcurrent device protecting the house at the garage!!

I understand exactly what you said zzz:D:D

(NEC 250.32 (B) Exception) good point but if your changing the service risers or meters or discos you may have to change that too its up to the AHJ at that point and once again depends on where you are.

Confusing enough?

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