Shocked from foil backed insulation and ductwork...

[RLyons]

This is a house we roughed and during the trim I was told people have been shocked from the foil insulation in the basement and the ductwork.

HVAC guy used a idiot tester to find it was the garage lighting circuit. I turn the circuit on and get 120v to ground (using dmm) touching either the insulation or ductwork. Yes the ductwork and insulation contact each other in random places.
I followed the homerun in basement from panel, along microlam, up laundry room wall to attic then dropping down to a 3 gang switch at the garage/house door.
I see no ductwork in either wall that I can see unless there is a jog somewhere.
Disconnect all the wires in the switch box and found that once the outside garage lights were removed the voltage was gone. There is no ductwork or foil insulation in the vicinity of this switch leg how could It possibly be getting any voltage? :dunce:

 

[Sierrasparky]

Either the hot is touching somewhere or the nuetral is connecting the circuit. Since you get 120v to ground I would say it's a hot . Probably a nail , any steel work ?

 

[milkman6453]

we're the ac lines through the attic or underground? the voltage could be going through one of the copper pipes. sometimes installers will use a metal line cover on the exterior of the garage. Another opossibility is if the lines were secured in attic maybe to the top stud on Wall. maybe a screw hit the wire?

I would bet it's related to the a/c installers work.

 

[jxofaltrds]

Did you test the switch legs to the lights? Did you remove the lights then reconnect the switch legs?

 

[starbolin]

What finish is the outside light mounted to?

 

[augie47]

What finish is the outside light mounted to?

that's my thinking (question) also.

 

[mopowr steve]

The interesting thing about this is that the duct work must have that rubber isolation section otherwise it should trip the breaker from a grounded ductwork via the ground wire at furnace.

 

[gadfly56]

The interesting thing about this is that the duct work must have that rubber isolation section otherwise it should trip the breaker from a grounded ductwork via the ground wire at furnace.

Well there's "shock" and then there's "SHOCK!!". Might be just enough to tickle your toes but not enough to trip the breaker.

 

[mopowr steve]

Well there's "shock" and then there's "SHOCK!!". Might be just enough to tickle your toes but not enough to trip the breaker.

None-the-less the duct work must not be grounded or there wouldn't be any toe tickling.

 

[RLyons]

Ill try to answer these in order of responses?

#2 No steel work all microlam main beams.

#3 HVAC runs from basement up to single floor house, no Attic duct runs and plumbing is all plastic.

#4 Tested all switch legs and pass through one by . Narrowed down to a switch leg that runs to 3 coach lights. Disconnect wire between 2^nd and last light voltage disappears.

#5 & 6 Finish is standard OSB, Tyvec with vinyl siding block to vinyl siding.

#7 You are correct there is a (not sure the HVAC term) flexible rubber connector for the main trunk and return lines before they hit the HVAC unit. So the overhead duct is hot but the ductwork directly attached to the furnace is not.

So another employee went today to take down the 3^rd coach light and when he put it back up he said he tested everything and voltage was no longer there. I am not satisfied with this resolve and think the circuit should be meggered. This is going to bother me and I feel the boss isn?t going to approve further investigation.

It kills me to wonder how is the voltage on the ductwork and insulation when the apparent culprit wire is nowhere near either ductwork or foil face insulation.

 

[Sierrasparky]

You verified this condition and now it went away.
I would not be satisfied unless I found the problem.
I would have a talk with the other guys on the job and see if they will fess up to something. Let them know you need to know and nobody will get into trouble. Stuff happens but in the end need to be repaired.

 

[GoldDigger]

What are the chances that the wire between the last two lights runs near something metallic which in turn contacts either the foil or a piece of ductwork?
A nail or screw into NM is a pretty common occurrence, especially if it is not stapled back from the edges of wood members.
Chances are good that it was close to the third light since manipulation of that end apparently made it go away temporarily.

 

[starbolin]

Ill try to answer these in order of responses?

#2 No steel work all microlam main beams.

#3 HVAC runs from basement up to single floor house, no Attic duct runs and plumbing is all plastic.

#4 Tested all switch legs and pass through one by . Narrowed down to a switch leg that runs to 3 coach lights. Disconnect wire between 2^nd and last light voltage disappears.

#5 & 6 Finish is standard OSB, Tyvec with vinyl siding block to vinyl siding.

#7 You are correct there is a (not sure the HVAC term) flexible rubber connector for the main trunk and return lines before they hit the HVAC unit. So the overhead duct is hot but the ductwork directly attached to the furnace is not.

So another employee went today to take down the 3^rd coach light and when he put it back up he said he tested everything and voltage was no longer there. I am not satisfied with this resolve and think the circuit should be meggered. This is going to bother me and I feel the boss isn?t going to approve further investigation.

It kills me to wonder how is the voltage on the ductwork and insulation when the apparent culprit wire is nowhere near either ductwork or foil face insulation.

Very kind of you to reply to all of us:thumbsup: I am left very concerned about the EGC on either the AH or the coach lights. Perhaps even some test has misled you as to their integrity. I am saying perhaps that it was the EGC that had the voltage on it and remounting the coach light cleared the fault.

You're not going to be able to track down a fault now that it has disappeared but you can check the EGC integrity.

 

[just the cowboy]

Are you sure there is no foil faced insulation outside under tyvek. Saw it one time, nail for siding went thru wire, it had foil faced fan fold insulation under siding and tyvak.

 

[mopowr steve]

I know you know what your doing but is there any chance that there are 3-ways on that lighting circuit that by coincidence your selecting a different switch to turn on lights and at times shows up as a live ductwork, leading me to say is it possible there is a nail into one of the travelers? As it may be possible that your 3conductor wire may be in proximity with ductwork somewhere?
Otherwise cowboy has a plausible explanation.