Horizontal vent for 75000btu Mr Heater

[JAMarkovich]

I know there have been several posts on this topic. I have the heater but it is not installed. It would be much easier to vent through the wall in my case. My 2.5 car garage is attached to the house with an unheated room above.

The main question is the clearance needed for the 4 inch vent pipe below the sofit. IF I extend the pipe out 12" past the gutter and facia, does this remove the issue of the vent pipe being 12" only below the sofit? I know there has been a reference made to 36" below the sofit for heat and fire clearance. I cannot find any clear cut reference to this in any of the local building codes.

I live in Northwest Indiana. The house is exposed to strong SW winds. The horizontal vent pipe would be directly in the path of the winds. Also, I was planning on using the B grade double wall 4" vent pipe.

Opinions? Help!!

 

[ishiboo]

When it comes to installation guidelines and code, it varies by every town, city and state and the product used. The last heater I installed had a 18" guideline from a "vented" soffit.

What I have seen does not dictate whether or not what you're proposing makes any difference - according to what I've seen here, I would still need 18" whether it sticks out far or not

If you can't find any reference, CALL your local inspector responsible for HVAC and ask! Thats why you pay them!

 

[CNCMAN]

I just installed a Mr. Heater Big MAXX 45000btu in a 400 sq ft work shop. I vented it out of the back. Worked great! Only needs 1" clearance from the ceiling.

 

[JAMarkovich]

Thank you for the information and the photograph. I did contact my local inspector. 12" below the soffit, vented or not is the code requirement for my locale in Indiana. The inspector mentioned sloping the pipe down for water drainage. The instructions call for a 1/4" slope up per foot of run for the vent pipe. I am going to use class B double wall for the vent. Also, there is no code requirement for how far the pipe has to extend past the wall. I am gong to use the 2' as shown in the Mr. Heater instructions.

So...the question remains upward slope or downward slope for the vent pipe. Is there a specific rain cap that should be used for horizontal venting or should I just use a 90"degree elbow facing down for termination.

 

[Andamo]

The photographs posted are very similar to my installation of my Reznor. I don't know what his looks like outside, but mine exits on a flat 2 story wall. I just left my cap in the horizontal position rather than turning it up 90 degrees. I did notice that when I was done the pipe had a slight uphill slope to it. I was concerned about the water, but after the past winter with the short run and powered exhaust, that isn't a problem at all. There appears to be enough heat in the exhaust to keep the water in a vapor form rather than letting it recondense in the pipe.
I also see a fan in his garage too. I have one also and it makes a huge difference keeping the heat even throughout my 3 bay.

 

[aveguy]

I have a MrHeater 75K which I installed myself about 2 years ago. At the time I had the same question you have regarding the 1/4" per foot up slope vs down slope. The install manual spec 1/4" up slope. But I wanted to use 1/4" down slope in order to self drain the condensate outdoors instead of having to build a condensate plumbing trap on the horz run indoors. The indoor trap would have been a freeze up issue for me since I don't heat the space 24/7. The issue with condensate is that some towns don't allow you to drain it to the exterior of a building. It's a tad acidic and you really don't want running down buildings or onto tops of people heads walking under. But at the same time I don't think you want it free draining without a trap back into the heater for corrosion reasons. I live in a rural setting and there is nothing on the backside of my garage that I have to worry about dripping on. So back 2 years ago during the install I contacted MRHeater Eng dept and asked if it was ok to use 1/4" per foot down slope instead of up slope and they said yes as long as I could pass code. So I used 1/4" down slope but I also have a very short horz run from back of heater to exterior wall. My only concern with down slope is that it doesn't allow the heater to naturally up draft and because of that I suspect generates a little more back pressure to the exhust system. That may lead to more heat & stress on the in-line exhust fan and also increases the positive pressure inside the combustion/exhust chamber which would lead to interior exhust leaks. Yes it's true that the unit has a power vent, but I suspect having the up slope makes a better draft. So if you do use 1/4" down slope I would keep your exit run as short as possible.

For what it's worth I use a stainless steel Tee Cap which is formed from the same size round tube as the exhust pipe. I have the exit "T" running parallel with the ground and a slight tilt for drainage. I used the horz orientation instead of vert because I didn't want the rain flooding into the open end of the tube assoicated with a vert orientation.

p.s. I think the ceiling fans are a great idea. I am going to pick up a couple of cheap ones and install. Should really help keep the heat down lower and better mixed. I climbed up on a ladder the other day near the ceiling and it must have been 20* hotter up there than down below.

Just got an email today(11/5/2010) from Northern Tool. The Mr Heater 75K(MHU75LP) is on sale for $480 (reg $550). Not sure about shipping(was free when I got mine) or even it that's a good price but maybe worth checking on if you are in the market.