Should I wall thimble or sleeve?

[Kepple319]

I’m in a predicament where I have Pellet vent pro 4” vent that I am exhausting horizontally through a cinder block wall. The kit is purchased came with a wall thimble, the issue is the thimble would require about a 7 inch diameter hole to be drilled whereas just piping it straight out would require about a 5 inch hole. Looking for advice for a couple of things here… if I use a wall thimble, how safe structurally safe is it to cut through the mortar joints and webbing of a cinder block foundation? Second question is if I use just the piping itself (which I’m leaning towards) and am able to cut a 5 inch circle in the hollow part of the block and run the piping out that was, should I use the top block or the second block down? The top block does have wood framing touching it and I just didn’t know how much heat would radiate into it without using a thimble. I know the clearance to combustible with this piping is 1” but the pipe would essentially be touching the cinder block and be able to radiate heat into the wood framing. Any input would be miraculous and thankful

 

[johneh]

In order for the cinder block to ignite dry softwood, the block would have to reach a temperature of 300 to 400
I see no concern in putting the pipe through a 5 in. hole . I would go through the block below the top block. When a pellet stove is running full heat, the stove pipe (double-walled), you can still put your hand on it. Uncomfortable, yes, but not near 300. Just my nickel's worth. Welcome to the forum!!