Concentric Venting - Wall thimbles?

[Ahuch]

Trying to vent a Reznor UDAS 45 in my attached (unfortunately) garage. Heater is hung on some strut channel already.

I have the proper Cat III (UL 1738) Stainless 4" Vent for the exhaust all ready to go, I have the overpriced concentric box adapter and some 4" galvanized vent for the intake air. I also have 6" galvanized vent for the concentric portion.

My challenge right now is wall thimbles, it seems like everything is rated for B-Vent and the 6" wall thimbles are all really 6-5/8" ID... but I don't want a giant gap that I have to seal between the thimble and 6" intake pipe.

Has anyone gone through this with the UDAS line before? It seems like a really uncommon venting scenario - when I talk to some HVAC suppliers they all look at me funny. I know I'm not a professional, but I've never run into anything like this before just trying to source materials for something that should be a fairly common arrangement?

Thanks!

 

[rlitman]

My understanding is that the concentric box adapter and thimble are a connected system, and they're not something you can piece together. i.e. a thimble made for b-vent or single-wall vent is wrong, and the concentric box should come with your thimble.

 

[Ahuch]

My understanding is that the concentric box adapter and thimble are a connected system, and they're not something you can piece together. i.e. a thimble made for b-vent or single-wall vent is wrong, and the concentric box should come with your thimble.

Can't post any images or links since I'm new to the forum, but Reznor sells the CC6 Horizontal thru wall kit (P/N 211762) and the installation instructions say to use a field supplied thimble to install it.

 

[thammel]

I used the Reznor cc6 kit. It worked well for me. I did not need to use a thimble because the outer pipe carries the intake so it's cool. The inner pipe carries the exhaust.