Reverberray 4” Vent Pipe question

[atvkid4eva]

I am finishing the install on my reverberray radiant tube heater. I am running the vent pipe, but I noticed when I slide the 4” 26ga vent pipe over the last heater tube there seems to be quite a bit of a gap. I will be fastening with a few self tapping screws and filling in the seams with high temp sealant. Will I have trouble sealing this connection with such a large gap? Or is this normal? Anyone else have one of these heaters and experience the same thing? See pic below:

 

[PoorUB]

Three screws and high temp RTV will be fine.

 

[jpaw]

I suppose could just seal and screw it. But you should really come off of the heater tube with single wall pipe and use the double wall when it penatrates anything combustible.
Also remember to pitch the exhaust slightly down so you don't trap moisture in the heater tubes.

 

[atvkid4eva]

I suppose could just seal and screw it. But you should really come off of the heater tube with single wall pipe and use the double wall when it penatrates anything combustible.
Also remember to pitch the exhaust slightly down so you don't trap moisture in the heater tubes.

The picture is a bit misleading, but coming off the heater is single wall. It’s a flexible elbow which makes it look like double wall. And yes, I have B-Vent running through the wall using a Thimble.