A seperate 92% funace for my garage

[Ernmang2]

Has anyone put in a seperate furnace for there garage with ductwork (attached garage) ? (not tying into the house)
I am working on this for my "best option" a 75k btu I want to be able to run pvc out the back (concentric vent...) and mount it horizontal up to the finished ceiling and have duct work come strait out. 800sq ft dont want it on the floor for fumes and also realestate. I looked at all the Hot dawgs/Lennox/Big Maxx/Dayton/Mr. Heater.....unit styles. For a sealed combustion the price about doubles and you still need a 5 inch vent with a min. of 12 inches out. and only 80%..... I can do a regular furnace sealed combustion with pvc vent for less than that. If anyone has done this please show me how it came out !
Thanks

 

[rickairmedic]

Ern I have done several of them although I dont have pictures of them its an easy install and works great in a garage . The last one I set up for a buddy I pulled a 100,000 BTU unit out of a 4 bedroom house which we mounted in the rafters of his 1 and 1/2 car garage . He can go from 20* to 75* real quick. We also ran 6" ducts off of the main trunk to each corner of his garage and also one over the workbench and one over where he stands when working under the hood of his car . The one we put oin was an 80% though if you are doing a 90-95% unit the most important thing is you will have to keep it on and set over freezing in the garage so it doesnt freeze . The unit freezing up can hurt the heat exchanger and many other parts that will have water in them .

Rick

 

[larry4406]

I put a 90+ unit in my detached garage (see pictures). The unit is horizontal and high up on the wall at the ceiling, in the middle back of the 4 car garage. I have 12 foot ceilings and can walk under the unit with no problems. The garage is 28x50. See layouts.

There are perimeter trunks along the wall which wrap around the sides to the front. There are also trunks running rear to front between the garage bays to get air to the front/middle of the space. Air distribution is nice.

The unit is ~100 kbtu/hr and I have a 5 ton AC unit. I think 5 tons AC is overkill as it does not seem to run long enough to get the hunidity out (I already had the outdoor unit, so decision was made).

I have a wall discharge concentric kit. As RickAirMedic pointed out, these make a lot of water, so you need to not only provide for a drain but never let it freeze. I ran my condensate to a sanitary drain (I have full plumbing in garage) and made sure to keep the drain on the interior side of the thermal envelope. I do not know of a freeze-proof method to dump the condensate out a side wall. I leave the unit set at 45F during winter, and within 5 mintues or so can have it up to 70F.

I have a future living space above the garage. Firestopping the trunks and unit was a PIA. All of the bulkheads have rear plywood against the side walls, the lids are FSK faced insulation. No interconnection to the future living space above.

Hope this helps.

-larry

 

[Tom2]

Thats a nice setup..

Yea, the only downside I see is trying to keep the condensate line from freezing. If you can overcome that, then you shouldnt have any problems. Keeping it at like 45-50* when youre not in it would be a good idea. (assuming the space is insulated) That would be cost effective as long as you used the garage every day or 2.

I installed a 100kbtu 92% furnace in my house. Around $1100. Its pretty simple. Just read the instructions thoroughly. I cheated with the drain line though..I just have it going to a bucket that I empty every week. I have a pump to hook up, but havent had the ambition to tear into my main pluming to tie it in.

If you dont have a drain, you could just run it to a big rubbermaid container.

 

[redsky49]

This could be a very cost-effective approach for conditioning your garage. Virtually every residential HVAC manufacturer has one or more "multi-poise" or horizontal indoor units for either furnace or heat pump applications. You are far more likely to get an aggressive bid price on one of these units than for a unit heater. As a side benefit, this unit should probably be a good bit quieter than a unit heater, especially if the duct design is done correctly.

For a ceiling-hung horizontal unit, the only real downside is the difficulty in servicing while standing on a ladder, and the slightly increased installation costs compared to a floor-mounted unit. The ductwork can be very simple, depending on the layout of your garage, and could be run concealed or exposed. The condensate discharge can be configured to slope by gravity or you may utilize a condensate pump if lift or a long discharge is required. Freeze proofing of the system can be achieved by selecting a thermostat that allows turn down to 40 degrees (frequently t'stats don't allow setpoints below 60-55 degrees). Unless you have some exceptional requirements, condensate drainage should be able to be configured so that if freezing conditions are encountered, no damage should be incurred. If you intend to provide cooling as well, position the equipment so that the refrigerant piping run from the indoor unit to the outdoor condensing unit is kept as short as possible. Discharge the condensate in compliance with local requirements.

Not certain where you are located, but typically the garage is not conditioned to the same extent as a residential unit. If reasonably well insulated, the HVAC requirements could be as little as 1-1/2 tons. The 75,000 btuh that you mention seems at first glance to be a bit high. Be certain to perform a load calculation. It seems that many of the posters on this site find out, after the fact, that they oversized their heaters and have less than perfect performance as a result. Size the unit according to typical conditions - not for record setting conditions. Place air outlets and inlets to "stir" the air as much as possible. Provide adequate fresh air in take. Coordinate duct placement with lighting layout/ceiling mounted equipment.

Be aware that many manufacturers have a substantial price difference between the high efficiency units (90%) and the super efficiency units ((96%). Unless you are utilizing the garage as occupied full time, it will take a long time to recover the increased initial cost of the super efficiency units. The best savings come from lowering the thermostat, especially when the space in unoccupied. Select from name brand units (Carrier, Trane, York, etc.). I have seen several 'off brands' that perform very poorly and end up being replaced by the owner.

Take lots of pics

Offered only as opinion

 

[rickairmedic]

I wouldnt put Trane or York or Lennox in my shed . Carrier is a good unit I am a dealer I also sell alot of Goodman units which are well built but cheaper mostly due to the fact they are not spending billions on advertising trying to get you to buy one. Trane in my eyes has gone down hill since the late 90's and is not the Cadilac they once were York I have never been fond of and Lennox is usually reasonable to install but if you ever need parts thats where they get you .

Rick