Cold air return in Detached garage.

[itsspeeds]

I am at the point of trying to figure out my ductwork for the 100,000 btu furnace I am installing in my 40x50 garage.
I am planning on putting the furnace on the floor (at least 18" off the floor). about the middle back wall. The garage is seperated with a wall and the furnace will be up next to the wall in the actual "garage section" of the building the other side will be more of a Mancave/living room area.
I want the heat to be the most comfortable possible and I want a clean look, so I am wanting to install the supply ducts in the ceiling with the returns on the bottom of the walls. So my question:
Do I install the returns a few ft above the finish floor? Is there a danger of the returns sucking in fumes as well? I don;t do much wrenchin here as my best fiend is a mechanic and we do it all there, but occasionally it has to be done here, so I don;t see a while lot of chemicals being spilled. Mostly gonna be used to park my extra vehicles. Thanks!

 

[39portlander]

Not sure were you got your furnace, but most heating/cooling distributors will have someone who can give you some idea's with some bldg./room measurements. For me they calculated heat and or cooling load and loss based on window's, ceiling height ect.

There's alot to consider, I'm not an engineer so they sell and can provide me with the properly sized equipment. The places I deal with do that any way.

 

[itsspeeds]

Thanks for the reply. The HVAC guy I have helping me is not to familiar with garage codes, since he has never done forced air in a garage, so I was just looking for some suggestions.

 

[metalTobman]

Your return intakes should go in at floor level. It sounds like you are heating the garage and the man cave with the same furnace. Be wary of carbon monoxide in the 'cave if you run engines in the garage.
As for drawing in fumes of any kind, it really does'nt matter if the r/a intakes are high or low, the fumes will find them.
If yopu look into it, you will probably find that local codes forbid heating a garage and a living space with the same forced air system.
Where is the thermostat going to mount? (in other words, will the garage side be happy, or will the 'cave side be happy?)

 

[itsspeeds]

I talked to my HVAC guy and we decided to leave the returns up about a foot off the floor. Mostly so that all the dust that settles on the floor doesn;t get sucked up.(i know there will be plenty of dust reguardless) The garage side is strictly to store my 99 Wrangler and my Harley, so there won;t be a car running much in the winter. I might just start them up once a month to get the engines moving, but I have a 9x18 door in front and a 7x9 in back that I will open to circulate air while they are running. The thermostat will be on the Mancave side. There will be a 9 x9 sliding barn style door that will seperate the two rooms. It will only be closed when we are in the mancave side watching a game of something.. It is technically all garage, but I am just making one side a little more "happy" than the other.