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#99892 - 09/23/06 09:47 AM Insulating Conduit from HVAC Duct  
Tiger  Offline
Member
Joined: May 2005
Posts: 706
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?

Dave


2017 / 2014 NEC & Related Books and Study Guides

#99893 - 09/23/06 10:02 AM Re: Insulating Conduit from HVAC Duct  
iwire  Offline
Moderator
Joined: Jan 2003
Posts: 4,391
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. [Linked Image]

Bob


Bob Badger
Construction & Maintenance Electrician
Massachusetts

#99894 - 09/23/06 11:58 AM Re: Insulating Conduit from HVAC Duct  
HotLine1  Offline


Member
Joined: Apr 2002
Posts: 6,872
Brick, NJ USA
I concur with Bob; did the AHJ reference a NEC Article?

John


John

#99895 - 09/23/06 03:55 PM Re: Insulating Conduit from HVAC Duct  
renosteinke  Offline
Cat Servant
Member
Joined: Jan 2005
Posts: 5,316
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 05:44 PM Re: Insulating Conduit from HVAC Duct  
Tesla  Offline
Member
Joined: Jun 2004
Posts: 1,273
Sacramento, CA
The noise from pipe on duct would trigger a warranty callback.

Duct transmits sound better than a drummer in the basement.


Tesla

#99897 - 09/23/06 07:32 PM Re: Insulating Conduit from HVAC Duct  
HotLine1  Offline


Member
Joined: Apr 2002
Posts: 6,872
Brick, NJ USA
Tesla:
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?

Reno:
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.

John


John


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