Propane heater venting

[Dave Sveden]

These are probably going to sound like very dumb questions but here goes. I'm venting a propane heater with a power exhaust. It has a 3" exhaust. The manufacturer requires a 3"-5" transition and the vent to be run in 5" pipe. I am planning on venting the unit horizontally. It is only located 18" from the wall it will vent through. The total run of vent pipe is about 3 feet.
I'm planning to come off the unit with a single wall 3-5" increaser and then immmediately transition to b-vent for my 3 foot run through the wall. I have a wall thimble to penetrate the combustible wall to the outside.
When these thimbles are installed, is the flange that will be on the inside of the building flush with the inside wall (so it is visible on the inside wall around the vent hole)? Is the outside flange installed under the siding, flat onto the exterior sheathing? Once the 5" vent pipe is passed through the thimble, what is the best way to seal the small space between the pipe and thimble walls? The exterior of my building is 10" cedar siding. How do I install a storm collar around the vent pipe with this siding? My siding has 8" of reveal on each run. Unless I breach the siding exactly in the center of a run, the storm collar will not sit flat on the surface around the vent pipe.
Thanks, D.S.

[Wgoodrich]

YOU SAID;
These are probably going to sound like very dumb questions but here goes. I'm venting a propane heater with a power exhaust. It has a 3" exhaust. The manufacturer requires a 3"-5" transition and the vent to be run in 5" pipe. I am planning on venting the unit horizontally. It is only located 18" from the wall it will vent through. The total run of vent pipe is about 3 feet.
I'm planning to come off the unit with a single wall 3-5" increaser and then immmediately transition to b-vent for my 3 foot run through the wall. I have a wall thimble to penetrate the combustible wall to the outside.
When these thimbles are installed, is the flange that will be on the inside of the building flush with the inside wall (so it is visible on the inside wall around the vent hole)?

REPLY;
I am questioning your use of what you are calling a B vent. If this appliance has no hood then are you just installing a 3/5" adapter then a single wall pipe to the thimble? Are you installing your own hood on a pressure vent that had no hood that came with the appliance? If your heater is a pressurized vent with no hood that comes with that appliance then that vent is not supposed to have a hood added. Just making sure. If you install your own hood for a B vent on a pressurized vent then the pressurized vent will push the exhaust fumes back into the house by way of that hood.


Wall flange will slide down the pipe thimble against the wall and is exposed on the surface of the wall as a finish trim.

YOU SAID;
Is the outside flange installed under the siding, flat onto the exterior sheathing? Once the 5" vent pipe is passed through the thimble, what is the best way to seal the small space between the pipe and thimble walls? The exterior of my building is 10" cedar siding. How do I install a storm collar around the vent pipe with this siding? My siding has 8" of reveal on each run. Unless I breach the siding exactly in the center of a run, the storm collar will not sit flat on the surface around the vent pipe.

REPLY;
I am a bit confused as to what you are using as a thimble.

If you have a pipe within a pipe and you can see between the pipes to the other end and beyond, then you just have a double or triple liner pipe not an outside thimble.

An outside thimble will have a weather and animal resistant hood mounted on the end of that thimble that just slides to the outside wall surface.

I would position that hood on the outside so that it will slide under the lip of that upper boards reveal as a rain shield.

Hope this helps some

Wg

[Dave Sveden]

Wg,
There is no hood on the unit. It's a Modine Hot Dawg heater. It has a 3" exhaust pipe off the back of the unit. All I have to do is come off that pipe with 3", increase the pipe to 5" and exit the wall 18 inches from the unit. I have to go a foot past the outside wall with the pipe before I put the end cap on per the manufacturers installation instructions. Since I need to go through the wall with b-vent (double wall), it was easier to start at the unit with it than to run single wall and then change over after less than 2 feet.
The thimble I have is to allow the pipe to pass through the combustible wall. It's just a two piece unit with a flange on each side and mating pipe in the middle. When the pipe is put through the hole in the wall for the exhast pipe, the flange is flush against the interior & exterior walls with the short sections of pipe mating inside the wall. This forms a insulated passage for the exhaust pipe to pass through the wall. I was just trying to confirm that I needed to remove the exterior siding to put the outside portion of the thimble flush against the sheathing under the siding. I'm still going to have to attempt the hit the middle of a row of siding to give me the best chance of having my storm collar/trim hit reasonably flush against the siding.
Thanks, D.S.

[Wgoodrich]

When you said B vent it struck me that you planned on installing a hood. Didn't think you were just wanted to make sure you were not.

What you are doing is fine. I understand your are using 8" reveal lap siding. If you can work your outside flange under the lap board above your pipe then you have a built in rain shield. If you have a problem getting the flange to lay to the siding because of the angle of the siding then you can install a second piece of your siding upside down to square off you angles laps as a filler piece.

Remember to caulk and seal your unit as it sets in place to insure against water leakage getting behind your flange in storms.

Good Luck

Wg

[Dave Sveden]

Thanks once again,
D.S.