Cold Air return location on overhead air handler in shop

[tlmartin84]

Which of the following would be best in an all around situation. I figured pulling the cold air from around the door would be good in winter but it adds to the length of lines that must be ran for electric, heat pump, drain, and thermostat lines. This being a shop that will be only heated on weekends, and minimally through the week (I will use a programmable thermostat). Is it worth the extra headache?

A side note is I am not running any ducting down for the cold air return. I want it high to keep dust out of the system.

This is my preferred routing.

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This might be better for efficiency...
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[dfiler2]

Keep in mind the cold air return will only work properly if it is pulling the coldest air in the room, which will be at the floor. I have a very similar situation I am trying get figured out, I am thinking of putting the furnace at the ceiling in the room you have marked "storage" for noise control. Then pulling the cold air from the far end of the room from about 18" off the floor. I am going to use a fabric ductwork, I installed a piece a couple of years ago in a retail store, it has worked really well and can easily be taken down cleaned out and washed. Here is a link to what I used. Kwik Duct I think you can also get a similar product with an internal spring for cold air, this would allow you to play around with the configuration to figure out what works best.

 

[tlmartin84]

My issue is dust. I create so much dust it is unbelievable. Low is better for heat, but then you sacrifice in the summer when cooling. Best design is two returns, one high for summer, one low for winter that have dampers to adjust.

I am just wondering if I am fooling myself into thinking that sucking the cold air that comes in around the door will help some......

 

[DC73]

My issue is dust. I create so much dust it is unbelievable. Low is better for heat, but then you sacrifice in the summer when cooling. Best design is two returns, one high for summer, one low for winter that have dampers to adjust.

I am just wondering if I am fooling myself into thinking that sucking the cold air that comes in around the door will help some......

I've been doing some research and planning the HVAC install for my shop that's currently being built. My take away is that the location of the return air intake for large open areas is less critical than making sure to have a return air system of adequate size.

I agree that high for summer, low for winter is best. But, I've decided to put mine up high for several reasons. My climate has winter but is more summer dominated. I also want to protect my system from dust overload. And, given that flammable vapors and such tend to sink, I don't want my return air anywhere near the floor.

I found this blurb on another discussion forum and my reading backs it up: "Placement of the return is only of concern in that it must be in an area that has an open path to it for the air from all conditioned areas to return to it."

I think you'd be better off with going with your first choice and centrally locate the return air. But, I also think that you definitely want a supply vent that blows air in the general direction of the door to help temper the heat loss/gain from the door.

DC

 

[dfiler2]

Good to know about the return air DC73, that helps me also. Thanks

 

[pseudorealityx]

If you're making as much dust as you're talking about, how are you addressing that problem? Dust collector?

 

[Criss]

I just did something simular to what your asking about. I have a 2 story 30 X60 garage. When the HVAC was installed they focused mostly on the 2nd story as this is the "hang out" area. Upstairs 6 supplies 2 returns, down stairs 2, 8x10 supplies and no returns. So upstairs was nearly 80 degrees while downstairs struggle to go up to 67 degrees. Although I added supplies and some other things, to address your question I made the furnace into its own filtered return air duct. I took the door that gives access to the two airfilters and cut in a filtered return duct. Obviously there is a lot more involved than just cutting up and installing. You'll need to calculate how large of a return and so on. I cover the returns and close the supplies upstairs in the winter so the warmth is drawn downstairs. In the summer, I close the register on the furnace I cut in and open everything up on the second story to draw the A/C upstairs.

 

[tlmartin84]

If you're making as much dust as you're talking about, how are you addressing that problem? Dust collector?

My shop will have an exhaust vent that will just pull it outside. My welding/mess table will have a hood over it with a LARGE fan.

Right now in the winter I just wear a dust mask in the garage until it settles then sweep it up. In the summer I do my grinding and cutting outside as much as possible.