Side Wall Thimble Install for Mr. Heater

[Miroslaw]

Hi everyone this is my first post. I am installing a Mr Heater Maxx natural gas unit in my garage and need some help with the stainless steel vent. I have a wall thimble and my question is- what size of hole do I cut for the 4" pipe which runs through the thimble?

 

[nwav8tor]

First, make sure the hole diameter of the thimble is the same size as the outer diameter of your vent pipe. If so, the hole you drill/cut in your wall should be the same diameter as the "slip canister" of the thimble. This is usually 2" more than your vent pipe diameter for double wall B vent (1" clearance all around the pipe) or the clearance required by the manufacturer of your vent pipe.

Paul