The 2" plastic condiut that feeds electrical lines from the circuit panel (unconditioned garage) to the attic and basement is essentially a clear path from the unconditioned attic to the basement. This allows freezing air to flow in from the attic to the basement. I would like to stop this airflow path.

I have been warned to not seal the end of this condiut with foam or caulk, as it will violate code. It will also allegedly make it difficult to add more lines. (I personally think latex caulk or foam from a can can be easily breached and resealed to add or replace romex.)

Is there an acceptable way to seal this? Can one seal the very end with caulk or expandable foam?

I attempted to stuff fiberglass into it, but as you would guess, it makes a poor seal; the seal needs to be airtight or nearly so.

At the moment I have duct tape around the end of the conduit, then latex caulk sealing the end of the duct tape. Thus, techincally I have not messed with the conduit. However, this is not even a semi-permanent solution, if it lasts one winter I will be surprised.


I live in NE Wyoming where it gets very cold in the winter. I am trying to seal all unnecessary air leaks.

Thanks!

Sealing the conduit as you mention is a good idea, and actually required by National code, to reduce or eliminate the formation of condensation, when conduits run from one environment to another.

If someone told you it is against code, there may very well be, for some reason, a local or state code waiving the national code.

Electricians normal use a moldable putty called duct seal, is is easy to form and insert in and around conduits, and is easy to remove later if the wires need to be pulled out or added to. And is rated to be near wiring.

Don't use foam or regular caulk, you will regret it.

Best I can suggest is to check with local code enforcement to find out exactly what you can do.

Excellent advice as always, tk; thank you

The previous advice/warning I got was consistent with yours, to avoid caulk or foam. They did not, however, suggest the putty.

Would you put it at all the accessible openings? Basement, attic, and panel box? Anyplace to NOT put it?

Plug the conduit at the point it enters the building from outdoor or the attic, and immediately at the opposite end, to keep moist air from filling the conduit's length from both air masses.

Caulk and foam are still OK around the outside of conduit and NM?

Yes, the problem with using the foam or caulk inside a conduit is when you want to add or change the wires, the foam and caulk get too hard and too deep into the conduit and grip the wires much more than desired.

Believe me, few weeks ago we went to pull out some #1 THHN out of a 2 " PVC, and it took one man two hours, with 3 other guys and the utility company waiting,and this was a do or die job, to get the damn stuff out so we could first pull out the old wires, and then make room for the new.

We found the foam inside a PVC conduit, the foam sticks to plastic very nicely, wrapped around all the conductors, alomast 2 feet into the conduit.

On the outside of cables or conduits, say to seal the hole through a wall after passing the cable/conduit through, no problem.