Hot Dawg heater exhaust temperature?

[Rick Schubert]

I'm wondering what the temperature the exhaust air is coming out of my 45,000BTU Hot Dawg heater. Foil tapes and heater resistant silicone have temp limits such as 325 degrees F and 500 degrees F respectively.

Will those be OK to seal the joints in the exhaust ducting?

Thanks, Rick

[Matt Meiser]

I'm wondering what the temperature the exhaust air is coming out of my 45,000BTU Hot Dawg heater. Foil tapes and heater resistant silicone have temp limits such as 325 degrees F and 500 degrees F respectively.

Will those be OK to seal the joints in the exhaust ducting?

Thanks, Rick

I used Loctite High Temp RTV from an auto parts store (the black stuff, not blue.) The specs for it were the same as a GE RTV that was recommended in the manual for my heater, which is similar to the Modine heaters but is not manufactured by them.

[Frank Hagan]

Just a guess based on other forced draft heaters in the 85% - 89% effeciency range that I'm familiar with ... your flue temps should be about 250 and lower. High temperature silicone is OK for flue pipe, but you really, really, really should use what the manual recommends. You really should. You REALLY, REALLY should!

The flue pipe will be "high pressure" compared to your shop. If you have any breech in that flue pipe, from an unapproved sealant that has broken down to a gap where its not put together well enough, you will push flue gasses into the room. You may not notice it, because if the heater is clean burning enough, only the odorless, colorless flue products are present ... like carbon monoxide.

An approved sealant and the foil tape, if that's what the manufacturer recommends, is a good choice. The products I'm familiar with use stainless steel or plastic pipe, and there is a procedure for making the joints tight (one type simply slides together, and is gasketed).

Also, make sure that your approved sealant is used only to join the pipes, sealing together two pipes that have a mechanical seal, and not used to fill gaps. We had a flue terminal that used the approved sealant to fill a 3/8" gap, and the sealant failed (in this case, no one died because the sealant only allowed flue gasses to be "re-breathed" into the heater, but it did cause quite a bit of nuisance shut downs for people). The stuff isn't made to hold up to the full assault of the flue gasses, and it will deteriorate.

[Randy Denby]

Rick, make sure you use double wall flue pipe. Especially where it will pass thru any structure, and leave 1.5" (total of a 3" larger hole than pipe diameter) around the pipe for clearance thru any structure, including roof if applicable. This is national code.Also make sure pipe has a positive pitch towards outlet. With double wall pipe, the outer wall temp. is low enough that foil tape is correct. Secure each joint with at least 3 sheetmetal screws. before taping.

[Matt Meiser]

Also, regardless of what you do and how, install a carbon monoxide detector.