Gas furnace choice for cool garage

digger_2

I want to replace the very old, salvaged, gas furnace in my garage. I would like to replace it with a unit that works efficiently at low temperature. The gas hog I have now (salvaged from a house to be torn down 24 yrs ago) will not operate without cycling on and off due to very cold air return temp when I set the tstat below 50F.

The building is a framed, 1000 sq ft, detached garage that I really only want to keep about 10* above freezing most of the time. I live in southern Indiana. Usually only a handful of below 10F nights per year. I don't have my heart set on a high efficiency model. Not sure if one would even work under these conditions.

Jean-David Beyer

Adjust something?

I have a building with two rooms in it. Each is a zone.  Each zone is heated by a Rheem hot air furnace (125,000 BTU/hr).  The building is not used much during the week,  so one zone is allowed to drop to 40F most of the time. There are no pipes in that side of the building. We try to heat the zone to 65F when the building is in use, and you can be assured that it takes quite a few hours to overcome a setback like that. The furnace does not cycle on and off due to low return air temperature.



I wonder what is causing your furnace to cycle off if the thermostat is unsatisfied. My guess (as a non heating professional) is that your furnace cycles off because its internal limit switch shuts it off because the furnace gets too hot inside before the thermostat is satisfied. This could be due to blower motor being too slow, blower too small, or inadequate ducts. You might wish to check this. Something is causing it to cycle off, and I cannot imagine how cold air would do that.

meplumber

Look into a Rinnai or Monitor Vented Space heater

Digger,

Take a look at the Rinnai or Monitor Space vented space heaters.  I have installed them frequently in this application up here in Maine and they work great if you are only looking to keep the garage around 50 deg.  Efficiency is good and the cost is too. 



The only way to really increase efficiency is to go to a condensing gas furnace and you will increase cost substantial.  Also check your local codes to see what is allowed in a garage.