EMT ran through AC ducting

[The Dog Father]

A co-worker says you can run EMT through AC duct work if it is in your way. I can only find info.(99 code) 300-22. Not sure if that answers my question? I would not install conduit in this manner. My co-worker says, show me in the code where you cannot. I refer him to 110-12.

 

[iwire]

Re: EMT ran through AC ducting

Yes you can install EMT in ducts if it is needed in the duct.

You can not simply run EMT through duct as a short cut. 2002 NEC 300.22(B)

 

[petersonra]

Re: EMT ran through AC ducting

Originally posted by The Dog Father:
A co-worker says you can run EMT through AC duct work if it is in your way. I can only find info.(99 code) 300-22. Not sure if that answers my question? I would not install conduit in this manner. My co-worker says, show me in the code where you cannot. I refer him to 110-12.

320.22 B does seem to allow this.

110.12 does not seem to apply.

I don't recall ever seeing anyone actually do it, but I guess I don't hang around in air handling rooms all that much.

 

[iwire]

Re: EMT ran through AC ducting

You know I may have been to quick on this one, it seems you could just cut through with EMT.

The restrictions only apply to Flexible metal conduit and liquidtight flexible metal conduit.

 

[sandsnow]

Re: EMT ran through AC ducting

You should check with the mechanical inspector.
The sealing of the penetration needs to be made properly. Obstruction to airflow is an issue to be considered.(size of conduit vs. size of duct)

If it's a cold air duct in an attic space you will have a condensation problem in the EMT if it is not sealed properly. That would mean a sealing point on either side of the duct. 300.7(A)

Seems like a lot of trouble, but if dot all your eyes you could do it.

 

[benaround]

Re: EMT ran through AC ducting

Don't forget to seal for the temperature change upon entry and exit.

 

[websparky]

Re: EMT ran through AC ducting

I think this would apply:

110.3(A)(5) Heating effects under normal conditions of use and also under abnormal conditions likely to arise in service.

 

[paul]

Re: EMT ran through AC ducting

Yes, you can. However I can also run 443 #12 THHN wires in a 4" conduit. Neither of which I have ever done, nor seen done.

 

[iwire]

Re: EMT ran through AC ducting

Originally posted by websparky:
I think this would apply:

110.3(A)(5) Heating effects under normal conditions of use and also under abnormal conditions likely to arise in service.

Only in as much as the conductors would need to be suitable for the ambient temperature and derated if needed.

 

[southernboys]

Re: EMT ran through AC ducting

Give me one week to get my digital camera and Ill bring you guys some pictures where some electrician did actually run the emt through a metal air duct. It simpily astounded me when I saw it. Now that I hear it may be permisable really astounds me. Wish I had my code book with me.

 

[LarryFine]

Re: EMT ran through AC ducting

I opened a 3-gang switch box and found an RG-6 running through the box, up and down. :roll:

 

[charlie tuna]

Re: EMT ran through AC ducting

dog,
water and electricity don't mix! when you run emt through an a/c duct and then run conditioned air through the duct it will condense the moisture in the air inside the emt and produce water.

we replaced a blown up 2000 amp bus duct in a twenty story office building because we were told they had a water leak in the elevator machine room. the water was coming into the cable tap box on the top floor. this tap box fed the mechanical switchgear located in the roof mechanical room and carried a heavy load. the mechanical room was pressurized due to the operation of five large fans --this force air down through the emt raceways(3-three inch runs) that ran horizontally ten feet inside a return air duct before turning down into the cable trasition tap box. the second time it blew up -- we traced the original problem to "water in the tap box".. this tap box was replaced on the first blow up and we could see that it was corroded from constant exposure to water on the second blow up!!! we sealed both ends of the emt to prevent the flow of air from the mechanical. then monitored the tap box to make sure it remained dry.

 

[The Dog Father]

Re: EMT ran through AC ducting

Thanks for all the replies! Even with the code saying it may be done, I would only do it if there was no other possible way and there usually is another way. I just cannot bring myself to an installation that looks wrong or cause heart ache later on. Besides once someone starts something like this in a building it soon becomes the standard for every other "who cares" installer.

 

[be4jc]

Re: EMT ran through AC ducting

You know on Oct. 1st in CA. that there will be a test for HVAC systems Called HERS test & it is a pressure test for the HVAC system so if you go poking holes into ducts be sure to seal them very well or they will not pass this wonderful new testing process !!! More paperwork :roll: