Horizontal Heater Vent Question

[Tjaltz]

I am installing a Hot Dawg 45K propane heater in a 2 car garage, at a height of 10 feet. I want to vent the unit out a rear wall (sheetrock, insulation, OSB and vinyl siding). If I am reading the Modine manual correctly, a horizontal vent with a power exhauster (positive vent pressure) is a Class III vent? I plan on using double wall pipe, but did not want to have a condensate drain in the garage. I was hoping to have my vent tilted slightly downward, to run any condensation right out the vent, what Modine calls "Horizontal Category III Venting with Downward Pitch (Condensate Drips Out End)". Has anyone installed their vent this way or have any problems with it? The heater will only be on when I'm using the garage, so the vent pipe will be cold prior to running the heater. Modine calls for a minimum of 3 feet of vent pipe. What I'm planning will have about 2 feet in the garage, go through a thimble in the wall, and then have another 12 inches protrude outside, for a total length of at least 3 feet. Does it matter is some of the 3 feet is outside?

Also, for anyone that has a Hot Dawg 45K unit, how much propane does it use, and what kind of run time are you getting. I was going to have a 200 pound (48 gallon) tank installed, hoping that would be large enough.

Thanks for any help.

 

[fatboy99]

I have my flue pipe slightly down hill and never had an issue with condensation. Where your vent exits the building is there a sofit ? I ended up putting in a longer pipe because moisture from the exhaust would rise up and condence on the sofit and make icicles.
I have a HHPI 45k heater similar to the hot dawg keeping my 24x30 shop 50 deg when im not using it and 70deg when working I use around 125 gallons a winter. Im in NE Indiana so your location may vary.

 

[stealthbob]

Just goes to show that anything you need to know has been asked before...

Exactly what I was going to post and nice to hear the answer.

 

[Teikas Dad]

My 45k Hot Dawg was delivered yesterday and I'm going to install mine with the vent pipe horizontal too. I just ordered a 3' section of Type B DuraVent pipe. I'm going through 3/8" OSB, 5 1/2 inch walls (2X6 construction), 1/2" plywood and 3/4" siding. Modine calls for 1/4" down pitch per foot so the end of the vent pipe must be 3/4" lower at the exhaust end compared to the back of the unit. The 3' minimum is total pipe length, just remember you need a minimum of 18" clearance on the back of the unit and a minimum of 11" from the outside wall to the end of the vent pipe.

 

[Tjaltz]

Thank you all for the information. It's very helpful.

 

[Mericleman]

I too am installing a Hot dawg 45K with a horizontal vent. Sheet rock, insulation, OSB, vapor barrier, vinyl, (2X4 studs). My question is how is everyone finishing the outside with vinyl? I can't see just sticking the thimble though the hole and leaving it like that right? Can I use a vinyl J-Block or something?

 

[Pac-Man]

Technically plain vanilla b-vent isn't considered "code" when venting horizontally, it's best to use the same vent pipe used with tankless water heaters which is an AL24-C grade stainless steel vent pipe. If you use b-vent you are supposed to use large diameter pipe and need a ton of clearance around the pipe when passing through the outside wall for fire clearance. I was able to drop to a 3" diameter pipe and matching wall thimble by using the stainless steel vent pipe (which is building code in many areas). Also with the stainless steel vent pipe you can rest assured it will never rust out.

I've got my Hot Dawg 75 setup with a 1/4" per foot downward slope and using a 90 degree termination pipe with no condensate drain tube. I have the pipe sticking outside the wall by over a foot so I didn't have to cut it and it gets the heat vapor nearly past the soffit and away from the side of the garage and I've had no ice dams of any kind (even when temps reach -40 below).

I purchased the vent pipe from Cinnabar Equipment Company after watching some of their educational videos.

http://www.stainlessventingandchimneyliners.com/boiler-ventingsingle-wall-single-wall-stainless-steel-c-62_11.html

Initially I cut around the vinyl siding enough so it didn't touch the pipe and I didn't have any problems with melting.

View media item 3524
Rest of the photo album is here:

http://www.garagejournal.com/forum/album.php?albumid=487

Now that I have upgraded my siding to LP Smart Siding (a wood based product) the contractor cut the wood siding 1" away from the pipe, a pretty big gap to chaulk, so I am ordering a roofing storm collar and will use the high temp chaulk to anchor it to the pipe and then use some matching blue chaulk to secure it to the wood siding to help ensure a water tight connection remains.

 

[mgilbert]

I have two questions...I'm installing a Mr Heater 80M BTU heater in my garage with horizontal venting. Q #1) I am venting out on a side with a 2' soffit, how far out do I need to go? Q#2) I see someone talking about 1/4" per foot downward slope but my manual says upward slope. Why are they different?
Thanks!

 

[SuperD]

Question 1: Check with your gas inspector for local rules, by exact code here we have to go 4 feet past the soffit venting material, but the inspector will allow 1 foot past the soffit if you remove the soffit venting material and replace it with solid sheet metal to 2 feet on each side of the pipe. The problem is the exhaust gases that go up into the soffit venting will eventually rot the trusses and and other wood framing.

Question 2: The confusion with the slope is the following. If you are horizontal Cat III venting for residential there is a restriction for the total horizontal venting length, usually quit short. The theory is if the total length is limited to 5 feet, it slopes back ( downhill) towards the furnace and there is enough heat in the exhaust to reheat the water vapor with the power venting. If you are in a commercial installation you can go over 5 feet total length, but now you will need a condensate drain near the furnace to deal with the larger amount of condensate draining back toward the furnace, again the same 1/4 inch per foot of slope.
To really complicate things, some venting pipe manufacturers advertise there pipe to be sloped toward the discharge cap at the wall. Best thing to do, if you are taking a permit out to install it make a visit or phone call to your local gas inspector, he has seen it done wrong against code so many times he will be glad to help you out.

 

[Pac-Man]

I have two questions...I'm installing a Mr Heater 80M BTU heater in my garage with horizontal venting. Q #1) I am venting out on a side with a 2' soffit, how far out do I need to go? Q#2) I see someone talking about 1/4" per foot downward slope but my manual says upward slope. Why are they different?
Thanks!

I do find it odd your manual only shows one option, back when I installed my heater in 2009 I was given a vertical (through the roof), and horizontal (up and downward sloping) options. I opted for the downward sloping vent pipe to avoid having any condensation running back into the garage where there is no drain or plumbing for letting any condensation water to escape properly.

I did research and for my 75K BTU Modine Hot Dawg garage heater it was easiest to use a 1/4" per foot downward slope and let any acidic condensation simply run out of the Z vent pipe behind the garage. In reality I have never seen any evidence of the "acidic water" running out of the Z-vent. The one thing I did learn is that it is important to use vent pipe made of AL24-C grade stainless steel to reduce the diameter of the pipe, and ultimately the size of the hole in the back of the garage, while never worrying about acid condensation rusting the vent pipe.

I downloaded the install guide for your MHU80 Mr. Heater and it says in horizontal venting installation bullet 5 to be 4' below or 4' extended horizontally beyond any soffit or under-eave vent. If you measure at an angle from my soffit vent to the vent pipe I'm probably closer to 3' but it's not caused me any issues; however, it may not be 100% up to code.

After having my siding upgraded from vinyl to LP Smart Side I added a storm collar and resealed the vent pipe seams with high temperature caulk (red). This is behind the garage and not visible from the street so it didn't have to be pretty.

View media item 6003

 

[Slowgsr]

My positive pressure tube heater.

Class C venting, downslope for drainage.
I used a firestop on the interior drywall 5/8 type x
Converted to b vent to go through the wall. The wall is non combustable. 5/8 type x, roxul, metal siding.

B vent should not be used except to penetrate the wall.

This is per my local codes.

 

[RichTJ99]

Pacman - does it have to stick that far out away from the house?

I am thinking of something similar for my garage (Modine hawt dog 75)

I am curious how far away it should be vented (the black circle is where i think it would come out).

Does it need to stick out 2 feet?

 

[smalltown]

RichTJ99 I believe that Pac-Man's vent is so long because of the sofit above it. My sterling heater manual states a minimum of 12" beyond the siding to prevent any issues with the siding. If you visit the Modine web site you can download the install manual for a Modine Hot Dawg it will give you all the information on the pipe lengths, and how far the pipe must be from nearby windows doors, and how high above the snow line etc. I'm not sure about the proximity to the overhead garage door. A call to Modine should clear that up.

 

[TractorJeff]

I too am installing a Hot dawg 45K with a horizontal vent. Sheet rock, insulation, OSB, vapor barrier, vinyl, (2X4 studs). My question is how is everyone finishing the outside with vinyl? I can't see just sticking the thimble though the hole and leaving it like that right? Can I use a vinyl J-Block or something?

The Big Maxx Horizontal Vent kit has a square piece to attach to the wall. My question is, "What do I do with sealing the Vinyl?"
Lot of money in the Vinyl siding and Yes, I admit I should have had all the penetrations figured out already!

 

[Disturbed Sledneck]

The Big Maxx Horizontal Vent kit has a square piece to attach to the wall. My question is, "What do I do with sealing the Vinyl?"

Lot of money in the Vinyl siding and Yes, I admit I should have had all the penetrations figured out already!

They make jumbo J-blocks. That's what I used.

Sent from my Pixel 3 XL using Tapatalk

 

[burkes69]

Technically plain vanilla b-vent isn't considered "code" when venting horizontally, it's best to use the same vent pipe used with tankless water heaters which is an AL24-C grade stainless steel vent pipe. If you use b-vent you are supposed to use large diameter pipe and need a ton of clearance around the pipe when passing through the outside wall for fire clearance. I was able to drop to a 3" diameter pipe and matching wall thimble by using the stainless steel vent pipe (which is building code in many areas). Also with the stainless steel vent pipe you can rest assured it will never rust out.

I've got my Hot Dawg 75 setup with a 1/4" per foot downward slope and using a 90 degree termination pipe with no condensate drain tube. I have the pipe sticking outside the wall by over a foot so I didn't have to cut it and it gets the heat vapor nearly past the soffit and away from the side of the garage and I've had no ice dams of any kind (even when temps reach -40 below).

I purchased the vent pipe from Cinnabar Equipment Company after watching some of their educational videos.

http://www.stainlessventingandchimn...wall-single-wall-stainless-steel-c-62_11.html

Initially I cut around the vinyl siding enough so it didn't touch the pipe and I didn't have any problems with melting.

View media item 3524
Rest of the photo album is here:

http://www.garagejournal.com/forum/album.php?albumid=487

Now that I have upgraded my siding to LP Smart Siding (a wood based product) the contractor cut the wood siding 1" away from the pipe, a pretty big gap to chaulk, so I am ordering a roofing storm collar and will use the high temp chaulk to anchor it to the pipe and then use some matching blue chaulk to secure it to the wood siding to help ensure a water tight connection remains.

you album link is dead I think. would love to see how you installed the storm collar.

 

[PoorUB]

you album link is dead I think. would love to see how you installed the storm collar.

This is an old thread and most of the people commenting in the thread haven't been on the group for a few years. I seriously doubt you will get a response!

Look at the age of the posts before you respond!

 

[Pac-Man]

you album link is dead I think. would love to see how you installed the storm collar.

Let's see if this link works https://www.garagejournal.com/forum/media/albums/garage-heater-hot-dawg.487/

 

[daws87]

I too am installing a Hot dawg 45K with a horizontal vent. Sheet rock, insulation, OSB, vapor barrier, vinyl, (2X4 studs). My question is how is everyone finishing the outside with vinyl? I can't see just sticking the thimble though the hole and leaving it like that right? Can I use a vinyl J-Block or something?

I built a J channel block out of some left over J channel the previous homeowner had stashed in the utility room and then carefully caulked behind it on the exterior side w/ some high temp silicone sealant (Red Devil I think). Two years later and zero issues.

 

[Pac-Man]

The z-vent pipe products come with a variety of termination hoods that are safe to use through vinyl siding especially when combined with wall thimble.

Termination Hood

Termination hood with screen is available in 3

www.z-flex.com