Voltage Between Duct and Foundation

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scottmac

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Location
amesbury, MA USA
I an wiring a new home and I was told by the HVAC contractor that he is getting a shock when he touches his duct and the foundation simultaneously. I looked at it and read 6-8VAC on a digital meter. I tried a bonding jumper from the duct to the foundation wall to create an "equipotential" (?) ground between everything but that did nothing. Next I shut down all power to the building. This included shutting off the temp service, and the service disco at the meter which was being fed temporarily from the temp service as permanent power has not been turned on by the utility co yet. I am still reading 6-8VAC. Could the HVAC equipment be causing this? This problem exists even when the house has been isolated from all known sources of electricity.
 
scottmac said:
I an wiring a new home and I was told by the HVAC contractor that he is getting a shock when he touches his duct and the foundation simultaneously. I looked at it and read 6-8VAC on a digital meter. I tried a bonding jumper from the duct to the foundation wall to create an "equipotential" (?) ground between everything but that did nothing. Next I shut down all power to the building. This included shutting off the temp service, and the service disco at the meter which was being fed temporarily from the temp service as permanent power has not been turned on by the utility co yet. I am still reading 6-8VAC. Could the HVAC equipment be causing this? This problem exists even when the house has been isolated from all known sources of electricity.
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Did you lift the incoming neutral at the service when you disconnected everything?

A bad neutral ahead of the service equipment will still result in voltage on the neutral and if you do not disconnect neutral also the problem has not been isolated. The problem could even be within the POCO primary neutral as it is also connected to the secondary neutrals throughout the system.

Lift the neutral in the service equipment, if the voltage disappears it is time to call the POCO - the problem is someplace ahead of the service equipment.
 
Could also be a neighbors bad neutral coming from the same XF. Probably going to be a POCO problem would be my guess.
 
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