Mr Heater Vent Kit - Stanless Steel Now Required?

[nwav8tor]

Finally getting around to getting the parts I need to install and mount a 75K Big Maxx NG Heater in the garage. I thought I'd be able to just buy what I needed locally rather than buying the Mr Heater vent kit with the unit since I wasn't sure at the time if I'd go vertically or horizontally. Due to the roof lines where I now want to mount it, I can't go vertical. For the horizontal install all I need is a 45 ell, 36" of 4" B-pipe, a wall thimble and the horizontal termination cap. I don't need the two 24" sections of standard 4" pipe or the 3" to 4" adapter that come with kits.

Unfortunately, I can't find what I need locally. Due to some recent WA state law, specialty stores won't sell vent pipe unless they install it and the big box stores don't have the horizontal termination caps I need (all I can find are 3" pellet stove horizontal caps). Sooo, I started to order the Hr Heater kit and Mr Heater's new catalogue lists part # F102860 for a 4" Horizontal Vent Kit - Stainless Steel to meet new 2012 requirements. But all I can find on-linje are the older F102845 kits that are apparently not stainless.

Is there really a new requirement to use stainless steel for a horizontal NG vent?

Thanks,
Paul

 

[dave67fd]

Only if it's required for your locality.

My guess is they either changed manufacturer's or their current supplier upgraded. Any price increase?

 

[nwav8tor]

Mr Heaters on-line catalogue doesn't list prices and I haven't found any of their retail outlets that have the new SS item to check the price...

I guess a call to my local code agency is in order to be sure.

Paul

 

[Mike007]

Is there really a new requirement to use stainless steel for a horizontal NG vent?

Thanks,
Paul

I don't think the requirement you speak of is new. As far as I know, B-vent has never been approved for category III type horizontal venting. B-vent is only approved for category I venting, the main difference being category I the vent system is under a negative pressure. As soon as you change to category III the vent system has to be sealed and typically resistant to condensation. B type vent is neither.

 

[danski0224]

I don't think the requirement you speak of is new. As far as I know, B-vent has never been approved for category III type horizontal venting. B-vent is only approved for category I venting, the main difference being category I the vent system is under a negative pressure. As soon as you change to category III the vent system has to be sealed and typically resistant to condensation. B type vent is neither.

This.

Type B vent is approved for vertical installation only.

Essentially, the CSA removed the UL listing from horizontal B vent installations for residential unit heaters.

Proof attached.

 

[nwav8tor]

OK - I think I've FINALLY got it straight.

I found the rating label on the BigMaxx and it says that it is a Category I unit heater. It requires 4" VERTICAL venting in the US and Canada and 4" HORIZONTAL venting is OK in Canada only. I wish it would have stated that horizontal venting isn't approved for US installations right in the owner's manual, it sure would have saved me the confusion.

I guess that just because there is an induced draft fan assembly it doen't necessarily mean that it's a Cat III venting situation.

So, now that I'm forced into a vertical vent situation, I guess I may have to move the planned placement of the heater to make the vent stack compatible with my garage's roof lines.

The problem I foresee is complying with this owners manual instruction:

"The vent must extend at least 3' (1m) above the highest point where it passes through a roof of a building and at least 2' (0.6m) higher than any part of a building within a horizontal distance of 10' (3.05m) unless otherwise specified by the American National Fuel Gas Code ANSI Z223.1..."

Does that really mean that if you have a 45 degree roof slope (1:1) and the vent will penetrate the roof close to the low edge of the roof (near the exterior wall) that the vent must extend 12' above the opening through the roof (since the roof within 10' horizontal will rise 10')? That seems excessive to me and it appears that the vent for my house's furnace doesn't extend anywhere near that high. Are there actually any exceptions to Z223.1 that allow for a shorter vent (such as the roof itself isn't considered "...part of a building..." or some other legalese considerations)?

Thanks,
Paul

 

[Steevo]

Sure glad I went vertical.

I was going to have to do the tall pipe above the roof thing in order to make those clearances, too. Instead, I did this:

Angled it through the attic, then up near the peak:

I did not want a big ugly smokestack pipe sticking up six feet out of my roof.

 

[nwav8tor]

I hadn't even thought of that approach!

Is that all B pipe in the attic since it's an unheated area?

Gaw'd I love this site!!!

Thanks for the idea...

Paul

 

[Steevo]

All of it is 4" B-vent. I added a collar of 8" single-wall with caps for the ceiling-to-top-of-insulation zone, so no insulation contacts the b-vent.

It looks like this now that the insulation is in the attic:

 

[Highbeam]

Looks real good steevo. I am jealous of your catwalk, I bet the insulation blower guys loved that.

 

[nwav8tor]

Steevo,

Now I'm finding info that eases the requirement to have the vent extend 2' above the highest building point within 10' horizontally. Apparently, that may only apply for vent diameters of 12" or greater or if narrower vents are within 8' of a vertical wall. I know it's too late for your install, but it might save me alot of grief and trouble with my install. There are tables that specify the height above the roof penetration point depending of the pitch of the roof.

Gas Vent Termination Table

Roof Pitch Minimum Height
Flat to 7/12 . . . . . . . . . . . . 1.0 feet*
Over 7/12 to 8/12 . . . . . . . . . 1.5 feet
Over 8/12 to 9/12 . . . . . . . . . 2.0 feet
Over 9/12 to 10/12. . . . . . . . . 2.5 feet
Over 10/12 to 11/12 . . . . . . . 3.25 feet
Over 11/12 to 12/12 . . . . . . . . 4.0 feet
Over 12/12 to 14/12 . . . . . . . . 5.0 feet
Over 14/12 to 16/12 . . . . . . . . 6.0 feet
Over 16/12 to 18/12 . . . . . . . . 7.0 feet
Over 18/12 to 20/12 . . . . . . . . 7.5 feet
Over 20/12 to 21/12 . . . . . . . . 8.0 feet
* This requirement covers most installations

Paul

 

[Steevo]

That would explain why all of the water heater and furnace vents I see around here are only a foot above the shingles.

I wanted mine near the peak anyway, due to prevailing breeze and the fact that it is on the shady side of the roof, where snow melts slowest.