Hot Dawg-Modine Heater Venting

[Randy French]

I am in the process of installing the 45K BTU Hot Dawg heater in my shop and had some questions for the venting of this unit. I've searched the forum and see that a number of you have this unit (or a comparable one).

I will be doing a vertical vent installation thru the roof and was wondering what size b-vent pipe I should be using? I see references to both 3" and 5" pipe size - is one preferred over the other? The local big boxes seem to only have the 3" pipe.

After connecting the pipes, should screws be used at the joints to hold everything in place? Or is this dependant on the manufacturer of the pipe? And once attached, should the joints be sealed with a high temp caulk or some foil duct tape? Or is this not needed?

Thanks for any help that you can provide!

[Russ Massery]

Randy, 3" is plenty for that unit. Screws wouldn't hurt, sealing it shouldn't be necessary. I didn't seal my friends I installed. There's no pressure in the pipe. be sure to use a flash collar and a storm collar. Hope it helps.

[John Gregory]

I have had one in my shop for 3 years now, and I love it. I did the horizontal exhaust too. 3" pipe and it works like a charm.

[Randy French]

Thanks for the info guys - this points me in the right direction!

[Ray Petri]

I have the 60,000 BTU unit with a 3" vent out the side of the garage instead of the top and works like a charm. Really heats up the garage in a hurry in the cold weather.

[Matt Meiser]

Randy, make sure you read the directions carefully. I bought a different brand, but on mine they said that the B-vent isn't supposed to be used except when passing through the structure. This is apparently because B-vent doesn't seal completely and the forced venting could force fumes out of the joints. There was a high temperature silicone to use to seal any joints. I ended up using standard flue pipe to a peice of B-vent that goes through the wall thimble.

[Randy French]

Thanks Matt - I will double-check the instructions to make sure that I can go with the b-vent for the entire run. The way I plan on running it is thru the ceiling, into the attic space, and then thru the roof.

[Frank Hagan]

You guys are killing me ... three or four times a year I talk to the survivors of carbon monoxide incidents, and once or twice a year to their heirs if they don't make it. :(

Read the instructions or call the company. Follow the venting instructions to the letter, even if it costs more, or is inconvenient. Unlike a table saw which will just cut off your hand, carelessness with a heater will take your life. And you won't know its happening until you are dead.

I'm very suspicious of using galvanized b-vent in a horizontal vent application (but if the instructions from the manufacturer say its OK, then it is). Usually its only allowed when the power venter is at the sidewall ... not when the blower is at the appliance itself and forcing the flue gasses horizontally through a pipe. Single wall and b-vent can be used in most vertical applications, but it must be the right size for the height of the vent. Finally, local codes may be more restrictive, and require triple wall vent pipe for any penetrations.

Don't cheat on venting. (Sorry for being so preachy ... its just that this is very important!)

[Randy French]

Frank - I don't consider it being preachy at all! You just want to make sure we are not doing stupid things.

The Modine instructions mention that b-vent pipe can be used in a vertical application, which is how I plan on installing it.

And even before seeing your posts about the possible CO dangers, I was planning on having a CO detector in the shop just to be safe.

Randy

[Frank Hagan]

Frank - I don't consider it being preachy at all! You just want to make sure we are not doing stupid things.

The Modine instructions mention that b-vent pipe can be used in a vertical application, which is how I plan on installing it.

And even before seeing your posts about the possible CO dangers, I was planning on having a CO detector in the shop just to be safe.

Randy

If you follow the instructions, you will be fine. The manufacturers can differ from the national codes if they submit their products for testing to approved labs, so their recommendations trump everything except more stringent local codes (if any).