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#99892 - 09/23/06 06:47 AM Insulating Conduit from HVAC Duct
Tiger Offline

Registered: 05/04/05
Posts: 714
Loc: Crystal Lake, IL USA
The cold water ground thread brought up an old issue. An inspector asked me to insulate a conduit from HVAC duct. I'm assuming the idea is that a ground fault will be carried by the conduit, not the duct. I'm not quite following the reality that conduit is running to the furnace, which is multiple screwed to the duct. Since it's bonded there, what's the purpose of insulating it anywhere?


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#99893 - 09/23/06 07:02 AM Re: Insulating Conduit from HVAC Duct
iwire Offline

Registered: 01/05/03
Posts: 4343
Loc: North Attleboro, MA USA
As there is no NEC section requiring this it seems your inspector just felt it was a good idea and you being the nice guy that you are you did it.

Bob Badger
Construction & Maintenance Electrician

#99894 - 09/23/06 08:58 AM Re: Insulating Conduit from HVAC Duct
HotLine1 Offline


Registered: 04/03/02
Posts: 6791
Loc: Brick, NJ USA
I concur with Bob; did the AHJ reference a NEC Article?


#99895 - 09/23/06 12:55 PM Re: Insulating Conduit from HVAC Duct
renosteinke Offline
Cat Servant

Registered: 01/22/05
Posts: 5305
Loc: Blue Collar Country
I think he meant "separate." While not mentioned (afaik) in the NEC, I was taught that my conduit was not allowed to touch other utilities; where contact was unavoidable, a thick pad was used to separate the two.

I was taught that this was to prevent wear caused by isloation; we could rub holes in out pipes, but not anyone elses'.

#99896 - 09/23/06 02:44 PM Re: Insulating Conduit from HVAC Duct
Tesla Offline

Registered: 06/16/04
Posts: 1280
Loc: Sacramento, CA
The noise from pipe on duct would trigger a warranty callback.

Duct transmits sound better than a drummer in the basement.

#99897 - 09/23/06 04:32 PM Re: Insulating Conduit from HVAC Duct
HotLine1 Offline


Registered: 04/03/02
Posts: 6791
Loc: Brick, NJ USA
Why would there be any noise? Conduit does not vibrate. There should be no vibration from the air handler/furnace either.

Not being a wise guy, but what do you base your comment on?

Yes, I also was 'taught' not to touch. I think Tiger has his furnace conduit strapped to the riser duct, which is common practice. I still don't see an NEC violation.



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