Air cleaner placement for most efficiency?

[Greg Urwiller]

I just picked up a JDS AirTech 2000 air cleaner for my workshop. My shop is about 25' square with a motel style htr/ac unit (can't think of the correct name right now) just off center on one side, about 3' up from the floor. I'm going to mount the air cleaner on the ceiling. Which way should I mount this to get the best air flow to and from the unit? Perpendicular to the htr/ac, in which case it won't matter which way the air flow exhausts out of the unit? Or, parallel to the air flow of the htr/ac? And, if so, I would imagine it should exhaust away from the htr/ac? I was figuring on centering the air cleaner, but if I put it in line with the htr/ac, then should I off set it back away from the htr/ac about 2/3's of the ceiling length? Thanks. Greg

[Andrew Duncan]

Howard Acheson provided a pretty definitive post on this back in 2008. It says:

This may be a little late but here is some info that could help.

Here are some general rules based on Nagyszalanczy's "Workshop Dust Control" and some of my own experiences and thoughts.

The two most important criteria for an air cleaner are the CFM and the filters. You want a CFM factor that will clean the size of your shop and a filter that removes the particle size that you are concerned about.

To determine the size or required air flow, use this formula: Volume of your shop (Length x width x Height) times Number of air changes per hour (typically 6 - 8) divided by 60. This will give you an answer in Cubic Feet per Minute which is how air cleaners are measured. MOST AIR CLEANER MANUFACTURERS RATE THE CFM OF THE FAN ONLY, but there are losses due to the filters. If you are building your own or if the air cleaner you are purchasing rates only the fan, figure you will lose about 25 - 40% for filtering losses.

As important as the air cleaner size is how and where you mount it. Try to mount at about 8-10 feet above the floor (no lower than 6'or 2/3 of the floor to ceiling distance if less than 8' ceiling). Mount along the longest wall so the intake is approximately 1/3 the distance from the shorter wall. Mount no further than 4-6 inches from the wall.

The exhaust is the largest determiner of the circulation pattern. You are trying to encourage circulation parallel to the floor/ceiling so ceiling mounting is not recommended. Use a smoke stick (or a cigar) to observe and maximize circulation. Use a secondary fan to direct air to the intake if necessary. Also, consider that a standard 24" floor fan moves a lot of air and, in some shops, just positioning it in a doorway with a window or other door open can accomplish as much or more than an air cleaner. It's all in the circulation patterns.

The exhaust is the clean air so that is where you want to position yourself. Do not place the air cleaner over the a dust producer. That will guarantee that the operator will be in direct line between the dust producer and the air cleaner. The operator wants to be in the clean air stream. If the dust has to pass your nose to get to the air cleaner, you get no benefits. If you have an odd shaped shop, two smaller units may be better than one large one.

DO NOT RELY ON A AIR CLEANER TO ACT AS A DUST COLLECTOR. The purpose of and air cleaner is to keep airborne dust in suspension and reduce airborne dust as quickly as possible AFTER THE DUST PRODUCER HAS BEEN TURNED OFF.

Finally, if you are looking for health benefits, you will not find any air cleaner manufacturer that makes health claims because there are few health benefits. CATCHING DUST AT IT'S SOURCE IS THE BEST LONG TERM GOAL. Rick Peters', author of "Controlling Dust in the Workshop", makes the point that spending your money getting the dust at its source is a better investment than trying to capture it after it is already airborne. If the dust is in the air, it's going to be in your nose and lungs too.

[Michael W. Clark]

Greg,
Ofter, those units are called a PTAC, Packaged Terminal Air Conditioner. It is recirculating the air in the room, and not introducing any outside air unless it has an economizer feature (small damper found inside the cover of the unit.

I would try to minimize the amount of dirty air going through the PTAC so its life is not prematurely shortened. I would mount the unit on the ceiling opposite the PTAC with airflow pattern perpendicular to it (along the long wall). If the PTAC is in the middle of the long wall, you could cheat the Air Cleaner back so that there is a greater distance from the outlet to the nearest wall than the inlet as mentioned above. I would mount it as high as possible. It it is only 6' off the floor, it is going to be in the way for a lot of tasks and you may be bumping into it constantly. I just got a JDS this weekend off of CL and will be mounting it soon. Mike

[Greg Urwiller]

Interesting. I don't really understand when one paragraph states to mount it 8-10' above the floor, which in the majority of rooms would be ceiling height, and the next paragraph says ceiling mounting is not recommended. Unless it means "solidly" against the ceiling?? Anyway, I'm hanging mine by chain from a 10' ceiling, so it will be at 8'+. I was considering hanging it 2/3's of the way across the room from the htr/ac. But Howard's advice is that the unit should go along a wall, 4-6" out. That's probably a better choice anyway. The htr/ac is on the north wall, mount this 4-6" out from the south wall, with the exhaust end on the opposite direction that the htr/ac is offset on the wall across. I originally figured the ctr position mounting would create a double circular motion. If it's by the wall, it would create one large, whole room rotation. Thanks. Greg

[Greg Urwiller]

Michael: I was typing when you were posting too! PTAC....that's it, just couldn't remember. Looks like we're on the same page here. I'll do just that. Picked this up off CL too last week. I've got a dust collector, just thought this might help pick up the fine dust that I miss. Thanks. Greg

[Michael W. Clark]

Michael: I was typing when you were posting too! PTAC....that's it, just couldn't remember. Looks like we're on the same page here. I'll do just that. Picked this up off CL too last week. I've got a dust collector, just thought this might help pick up the fine dust that I miss. Thanks. Greg

Same for me. I'm replacing a box fan with filter arrangement. I figured it was an upgrade, and for the price, I could by the fan and controls from an HVAC dealer.

[Howard Acheson]

Greg, I think you missed the parenthetical statement that followed the 8' statement. Here it is again. "Try to mount at about 8-10 feet above the floor (no lower than 6' or 2/3 off the floor to ceiling distance if less than 8' ceiling)."

[Bernie May]

One of the best investments I ever made for my shop was a Dylos DC1100 air monitor ($200). Takes the guesswork out of what your dust collector and air cleaner are really accomplishing. this is thetool you will turn on first when you walk into your shop.

[michael osadchuk]

Interesting. I don't really understand when one paragraph states to mount it 8-10' above the floor, which in the majority of rooms would be ceiling height, and the next paragraph says ceiling mounting is not recommended. Unless it means "solidly" against the ceiling?? Anyway, I'm hanging mine by chain from a 10' ceiling, so it will be at 8'+. I was considering hanging it 2/3's of the way across the room from the htr/ac. But Howard's advice is that the unit should go along a wall, 4-6" out. That's probably a better choice anyway. The htr/ac is on the north wall, mount this 4-6" out from the south wall, with the exhaust end on the opposite direction that the htr/ac is offset on the wall across. I originally figured the ctr position mounting would create a double circular motion. If it's by the wall, it would create one large, whole room rotation. Thanks. Greg

Greg,

I'm not familar with care of PTAC/air conditioners but I know that if you were installing two air cleaners in a workshop you would install them against the opposite longer walls - in accord with Howard's description - so that the possibility of ONE circular air flow around the room is maximized.
The small dust particles that the air cleaner traps may be suspended in the air for an hour or more before they get sucked into the air cleaner so you want to minimize the likehood of eddies/dead zone immune from one circular pattern.

Without knowing about PTACs I would be tempted to see in, in part, as an aircleaner, and fit the front of it with a dust trapping filter.

good luck

michael