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The inter-system bonding termination (IBT) is where other services like telephone and cable TV get their ground bonds from the house's grounding electrode system (ground rods).

2014 NEC (NJ) 250.94 seems to say that an IBT must be placed in proximity to the house service. My home currently has a main panel with main breaker as the service disconnect. I am in the process of installing a whole-house transfer switch for a generator, which then becomes the service entrance equipment. My understanding is that the wire between the transfer switch and main panel becomes a feeder in that case (and necessitates isolating neutral and ground, etc.)

Am I required to relocate the IBT to near the new transfer switch, which is about 60 ft away on a different location on the house closer by the generator? (There was no additional room in the utility room for the transfer switch, so it is being mounted in a protected location outdoors.) All of the communications wires for the house already terminate by the existing IBT, so this would result in a rats nest of 5-6 wires having to be spliced and then traveling over to the new IBT location. For all practical purposes, this seems like a bad idea.

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    Are you moving the service drop and electric meter to the generator shack? Is this being wired by the generator company?
    – Harper - Reinstate Monica
    Jun 16, 2019 at 12:40
  • Why are you going with whole-house transfer BTW? Is having a standby subpanel not an option for you for some reason?
    – ThreePhaseEel
    Jun 16, 2019 at 13:25
  • @Harper The service is moving underground and next to the new transfer switch, which is in a different area of the house from the old OH meter. There's no generator shack, its a freestanding exterior generator. I'm doing the generator myself.
    – David Pfeffer
    Jun 16, 2019 at 20:49
  • @ThreePhaseEel Nearly every load in the house is something we'd possibly want to have during a long term power outage. I work from home, and we're in the country and have well/septic/etc. Overall, it wasn't worth it.
    – David Pfeffer
    Jun 16, 2019 at 20:51
  • @DavidPfeffer -- nods are your heavy appliances (water heater, range, dryer, central heat) electric or gas?
    – ThreePhaseEel
    Jun 16, 2019 at 20:57

2 Answers 2

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Leave the ground rods. Install a second set at the new service location.

The IBT only needs to go to ground rods. It doesn't need to go to particular ones.

This plan depends on there being a ground wire between the old and new rods; it's a rare time when metal conduit shell, water pipe, etc. won't do.

There is no penalty for more ground rods than the house requires.

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    That only works if there's a wire-type EGC between the two locations (not conduit or such), otherwise it violates NEC 250.121...
    – ThreePhaseEel
    Jun 20, 2019 at 0:55
  • @ThreePhaseEel well there would need to be, wouldn’t there, if the service point was being moved there?
    – Harper - Reinstate Monica
    Jun 20, 2019 at 2:31
  • Well, it could be the case that the wiring was done using a method that supplies the EGC some other way. I agree that in residential, it's likely that the EGC is a wire...
    – ThreePhaseEel
    Jun 20, 2019 at 2:38
  • 250.94 states, "... at the service equipment or metering equipment enclosure..." I do already have a new ground rod at the new service location, and then am reusing one of the original ground rods via a wire that runs into and back out of the house to get to it. I'm concerned only with the physical location aspect of the code. From a practical perspective, the bonding is completely fine.
    – David Pfeffer
    Jun 20, 2019 at 12:12
  • @ThreePhaseEel fixed.
    – Harper - Reinstate Monica
    Jun 22, 2019 at 1:10
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I would say you are fine. And it should be outside near the meter location. I keep reading 250.94 and can not find any violation. The only thing i see is if you add ,phone or cable out to the other building. You may have to add a ground bar or IBT. But there are exceptions on existing saying not required.

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  • I'm not sure if this impacts your answer, but, there's no "other building." Its just my residence and a generator.
    – David Pfeffer
    Jun 16, 2019 at 20:52
  • The new meter location is not near the old IBT.
    – David Pfeffer
    Jun 16, 2019 at 20:53
  • I thought it was in a shed.. Will look at it more. Still think your ok .
    – user101687
    Jun 16, 2019 at 21:13
  • So you are adding a new service. New meter,transfer switch, and disconnect. At new location ? And making existing panel a sup- panel. You have to bring water bonds out to new service,,gas bond if gas ect.
    – user101687
    Jun 16, 2019 at 21:24
  • All plastic water piping. The gas is bonded directly to the wires going to the ground rods, and I've connected into that wire wand extended it along with the service wires to the transfer switch. The IBT is on one of those wires too, its just not in proximity to the new meter, service disconnect, etc.
    – David Pfeffer
    Jun 16, 2019 at 21:28

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