What is the best direction for an overhead gas furnace to be pointing in a garage with 2 overhead doors?
Answers:
There is so much bad advice given on this site it is unbelievable. Don't answer questions unless you really know the answer. Place the heaters on the opposite wall from the overhead doors. Having the air blowing toward the open door will reduce the amount of cold air coming in and the temp in the garage will recover quicker once the doors are closed. Positioning them the other way will encourage cold air to rush in.
Other answers:
Away from the doors to help keep the heat in.
Away from the doors to help keep the heat in.
Heat sources in a home are generally placed near doors and windows due to the fact that those areas are the coldest because there is a much lower R-value to doors and windows than there is in walls.
The same is true in garages, assuming the walls are insulated. If the walls are insulated, the warm furnace air should be pointed towards the overhead doors. If the garage walls aren't insulated, I don't think there is a wrong location.
If you're talking about a unit heater then point it at the opposite wall to get the air circulating through out. If its a radiant type then hang it in the middle of the ceiling pointing down.
What Rickster said.
Heat rises, so when you open the doors, the heat will want to escape out the top while cold air rushes in from the bottom. With the heater near the doors and up by the ceiling, pointing inward away from the doors, you have a draft in the opposite direction. You won't lose as much heat when you open the doors.
Edit: dfiler2, open your garage door later tonight when it's cool. You see that the cold rushes in from the bottom, warm rushes out at the top. The fan in the heater needs to be placed to reverse that and keep the warm air at the top from escaping.