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-   -   Install Help on 75K BTU Garage NG Furnace (http://www.diychatroom.com/f17/install-help-75k-btu-garage-ng-furnace-120111/)

live4spd 10-14-2011 01:05 PM

Install Help on 75K BTU Garage NG Furnace
 
I have a 32x26x12' high garage that I'd like to heat full time for winter. I have purchased a Mr. Heater 75000 BTU Garage/Shop Natural Gas furnace for this task.

I have a question regarding the flue install. Several homes in my area have this type of unit, all were professionally installed with a roof chimney. Since I'm doing it myself, I don't want to put more holes through the roof and would like it to exhaust out an exterior wall.

But I'm not sure how the thimble goes through the wall with respect to the vinyl siding. Does the metal thimble have to go thru a square box vinyl siding peice or get covered by the square box with a hole for the pipe. Also what type of sealant should I use for the thimble against the house wrap / or vinyl siding square? Fire stop caulk?

How far does the exhaust pipe have to be from the soffitt and how far does it have to extend from the exterior wall?

Thanks for the help, trying to do a good job up to code, just not sure of the codes to follow.

Beware that the gas line hook up will be done by a pro, and tested. Not interested in doing connections there.

gregzoll 10-14-2011 02:57 PM

Call a roofer to do it. As long as you have materials, the job should not be more than maybe $150 to $250 at the most for labor.

Technow 10-14-2011 03:05 PM

Quote:

Originally Posted by live4spd (Post 748670)
Beware that the gas line hook up will be done by a pro, and tested. Not interested in doing connections there.

But that's a connection that can pass the "sniff test"......CO from the flue just puts you to sleep forever.....

live4spd 10-14-2011 03:22 PM

Hire a roofer for that really? What's the advantage of the roof vent versus horizontal vent. Just doesn't seem that hard to do, I'm trying to justify why it should go vertical, etc.

bob22 10-14-2011 03:42 PM

THe install instructions show 12" space minimum from wall overhang to termination cap.
Have you read the instructions? If so, and it they are still not clear, I'd pay someone who knows how to do it and sleep better at night. Might want to check into a chimney repair, fireplace installer for installation.
Instructions for the thimble may provide guidance for your other questions re: sealing etc...

raylo32 10-14-2011 07:24 PM

The other thing I would look at is sizing. 75KBTUH for one room, albeit a big one?? Seems waaayyy oversized. It might be semi-reasonable if you only heat the garage part time and want a rapid warmup when you head out there. But for full time heating of such a small space a much smaller unit should suffice.

live4spd 10-14-2011 07:28 PM

Well far as sizing I need 60k according to the pros. But only the 45k and 75k are readily available.

raylo32 10-14-2011 07:42 PM

Maybe so, but seems way off base to me, unless uninsulated in the Yukon... or perhaps the pros are sizing it for a part time fast heat up scenario as I mentioned. If you don't want to pay for a proper heat loss calc try the link below. It will give you a fairly accurate estimate and a reality check for what they are telling you.. I really don't believe 60K just for a garage... but that's just me.


http://www.builditsolar.com/Referenc...s/HeatLoss.htm

raylo32 10-14-2011 07:55 PM

I just ran your scenario on that calculator assuming no windows and a 10 degree F design outside temp (it has a built in 70 degree inside design temp) and got 35K BTUH heat loss. Also assuming R20 ceiling and R10 walls. This would make the 45K unit about right for you and sounds a lot more reasonable to me. Not definitive... just another data point for you.

live4spd 10-14-2011 08:02 PM

Well appreciate the work. FYI this is in Fargo ND so outside temps can be -30. Might figure differently in the calculation.

live4spd 10-14-2011 08:03 PM

Raylo32- what's your opinion on horizontal versus vertical exhaust?

raylo32 10-14-2011 08:11 PM

Well, -30 F calc gives 48K heat loss. Not sure how often you get that... or why you would be in the garage then. But I am sure glad I don't live there!

I will defer to the pros on the venting question. I assume you are talking about an 80% efficient type B vent. I have never seen one of those that didn't go out the roof. If horizontal is allowed I would be very careful as to the code and all specificed clearances and overhangs. They exist for a reason.

What I would do is get a high efficiency condensing furnace that can be more readily vented horizontally (still lots of clearance and overhang requirements) and also save a lot of $ over those long cold winters.

Quote:

Originally Posted by live4spd (Post 748936)
Raylo32- what's your opinion on horizontal versus vertical exhaust?


raylo32 10-14-2011 08:17 PM

Oh, I have to revise the first 10 degree loss calc. It had a default value for a floor loss (I assume this is a garage on slab) that I neglected to zero out.

So the calcs show:


10 degree F design temp: 29K
-30 degree F design temp: 48k

live4spd 10-14-2011 08:24 PM

Well either way that's alot closer to 45k than 75k.

Alright thanks for the advice.

a7ecorsair 10-14-2011 09:06 PM

Quote:

Originally Posted by raylo32 (Post 748940)
Well, -30 F calc gives 48K heat loss. Not sure how often you get that... or why you would be in the garage then. But I am sure glad I don't live there!

Ya got to keep the snowmobiles running:thumbup:
Sometimes you have to fix the snowblower:laughing:
Sometimes it gets to -40 in Fargo:eek:


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