Another Heater Venting Question

[cidsamuth]

Okay, so I have read about 1001 threads on this forum on the subject, but nothing exactly on point.

I bought a monster Mr. Heater 125k BTU heater (overkill, I know), converted to propane. It's up, and everything is done but the venting.

The hole is already cut for horizontal venting, so I'm locked into the idea. I had made the mistake of purchasing B-vent, double wall piping, and I now know I need Category III stainless instead. I have already installed a 1" clearance thimble in the wall, through which I had already started running the B-vent that is getting removed.

Here's my 1st question: Does any part of the Category III stainless need to be double wall (which seams hard to find)? Mr. Heater tech support wasn't terribly helpful here, and he kept just saying "Type 3B." I'm trying to decide if the Cat III requirements mean single wall only throughout, double wall only throughout, or perhaps double wall only as it penetrates through the exterior wall to the end cap.

2nd question: Unfortunately, I made the hole in the wall such that the vent pipe extrudes within about 18" of the soffit. I see now that Mr Heater instructions say it needed to clear by 4', but I don't know that's actually code where I'm at. Should I just make sure the vent extrudes far enough out that the endcap clears the soffit to avoid moisture going into the attic? I was also thinking I could use a 45 degree angled DOWN end cap to push the gas away from the soffit. There is no traffic below that point of the garage, and it's a solid 12' in the air.

Thanks

 

[Jackfre]

Cat III pipe is SS, negative pressure and non-condensing. I am not aware of any “double wall” Cat III piping. As well, I think you are confusing “double wall” with “direct vent.” DV draws the outside combustion air through the outer pipe and exhaust thru the inner pipe. It is a sealed combustion system. Look at the clearances of your Cat III pipe. Look at the manuf directions AND FOLLOW THEM.
No inspection dept will go against the manuf suggestions on venting. Nor should you. You are building this entire system around a hole you made in the wall before you knew what would have been correct. Back up a bit and start over. You will be happier.

 

[cidsamuth]

Cat III pipe is SS, negative pressure and non-condensing. I am not aware of any “double wall” Cat III piping. As well, I think you are confusing “double wall” with “direct vent.” DV draws the outside combustion air through the outer pipe and exhaust thru the inner pipe. It is a sealed combustion system. Look at the clearances of your Cat III pipe. Look at the manuf directions AND FOLLOW THEM.
No inspection dept will go against the manuf suggestions on venting. Nor should you. You are building this entire system around a hole you made in the wall before you knew what would have been correct. Back up a bit and start over. You will be happier.

Okay, check on the Cat3 being single wall. Does that put it's OD as 4", or is it 4.62" like the Type B double wall? Asking so I know whether the wall thimbles are interchangeable. It's not like this stuff is readily available at the local Home Depot to look at. I have to order everything.

And then the next question is whether I can get away with keeping it vented underneath the soffit if I extend the vent out far enough out from the wall to clear said soffit, or whether I'd still end up with fumes in the attic. The alternative is going through the considerable trouble and expense of repairing that hole and venting out an adjacent wall with no soffit.

I know what the "right" way would have been if I knew, so please no lectures. I'm trying to figure out a reasonable course of action given where I'm at right now.

 

[Jackfre]

2ZVWB04 - Z-FLEX 2ZVWB04 - 4" Z-Vent Water Heater Horizontal Vent Kit w/ Backflow

Z-FLEX 2ZVWB04 - 4" Z-Vent Water Heater Horizontal Vent Kit w/ Backflow - In most applications, kit contains the components you need all in one box to vent a 4" tankless water heater. Designed for horizontally vented heaters mounted to an outside wall. Back-flow preventer is included for cold...

www.supplyhouse.com

Z-flex is a good outfit. You may end up with a couple soffit issues with the 18”. Remember that flue gases are saturated air. depending upon wind direction, temps, etc you can end up with serious icing issues. taht mosture in the shoulder seasons can lead to mold, etc problems. If you extend the vent i would suggest that you box it in.

 

[cidsamuth]

2ZVWB04 - Z-FLEX 2ZVWB04 - 4" Z-Vent Water Heater Horizontal Vent Kit w/ Backflow

Z-FLEX 2ZVWB04 - 4" Z-Vent Water Heater Horizontal Vent Kit w/ Backflow - In most applications, kit contains the components you need all in one box to vent a 4" tankless water heater. Designed for horizontally vented heaters mounted to an outside wall. Back-flow preventer is included for cold...

www.supplyhouse.com

Z-flex is a good outfit. You may end up with a couple soffit issues with the 18”. Remember that flue gases are saturated air. depending upon wind direction, temps, etc you can end up with serious icing issues. taht mosture in the shoulder seasons can lead to mold, etc problems. If you extend the vent i would suggest that you box it in.

Thanks, I appreciate the feedback. I'm leaning toward biting the bullet and running the vent out a different wall . . . with all the pain of repairing the first hole.

As for the soffit . . . I was under the impression that fumes getting into the attic via the soffit was a bigger deal than the moisture concern.

 

[Jackfre]

Certainly fumes are important, but you will have a couple CO detectors to ensure that you are not a victim.

 

[TractorJeff]

This comes up every year, all with different answers. (IIRC?)
I think that the solution was/is to extend the pipe out further from the Soffit, not necessarily down from the Soffit?

 

[Showkey]

Okay, check on the Cat3 being single wall. Does that put it's OD as 4", or is it 4.62" like the Type B double wall? Asking so I know whether the wall thimbles are interchangeable. It's not like this stuff is readily available at the local Home Depot to look at. I have to order everything.

And then the next question is whether I can get away with keeping it vented underneath the soffit if I extend the vent out far enough out from the wall to clear said soffit, or whether I'd still end up with fumes in the attic. The alternative is going through the considerable trouble and expense of repairing that hole and venting out an adjacent wall with no soffit.

I know what the "right" way would have been if I knew, so please no lectures. I'm trying to figure out a reasonable course of action given where I'm at right now.

Your location is not noted but there are some BIG BOX stores ( Menards) that stock CATIII venting…….so you can touch and examine the parts required.

https://www.menards.com/main/heating-cooling/venting/high-efficiency-appliance-venting/c-9520.htm

 

[FMB4]

CO detectors can save your life. But what if nobody is home and you have pets? Sure, a CO detector equipped Smart Security system can notify you of a CO problem but that might be too late for non-humans. This type of work must be done to code and, in many cases, will need to permitted.