We run a cabinet shop and do our own finishing. Our air make-up unit becoming quite a problem since we moved into a new building. The air make-up unit for some reason cannot have any external filters or it restricts airflow. Well today, problems with our dust collector and a nice coat of sawdust and chips on a freshly coated kitchen. Anyone have an insight into this? There has to be some kind of solution to filtering outside air. It's not my department but I'm searching for answers.

We retrofitted our units to use merv 8 pleated filters outside and had the ducting from each unit modified with new ductwork to have merv 10 pleated filters...… weve had zero flow issues when the filters are in good shape..... we also attach fiberglass spray booth material to the bottom of the intake to catch the biggest debris.... Our makeup units are less than 50 feet from a busy road! So filtered booth air was a must have.... Our units are quiete large as well so airflow was not a problem with large units...

If the manufacturer won't help then call an HVAC specialist. There is almost certainly a way to add filters to any make up air system.

John

I think if you got more airflow you would have less dust, maybe there isnt enough air so it pulls everything, we have no filters and have very little dust issues

thanks for the tips, appreciate it

One of the issues is when we use external filters right now they are freezing up and shutting down the system. We're trying to get something custom made. But it's like pulling teeth right now.

air make up units are designed to have intake filters either polyester ring panel filters or some units use a type of filter similiar to the one above your stove.

have you checked the rpm of the unit and checked the belts, if you can't get air thru it have you looked at the outbound ductwork did it get smaller meaning did you get new ductwork that might be increasing your static pressure...also do you have an discharge plenum, typically what i do is have 20-50 ring panel filters on the intake and a higher effeciency tackified panel filter on the discharge plenum, i am thinking you have a problem related to static pressure perhaps coming from the motor , was it reversed accidently?

good luck
herb j

It was an older unit that we never had to run filters at the previous location. Now we find we need to but filters are no longer made to fit. It was installed and setup by a mechanical, electrical and HVAC contractor. I guess we need to push them to modify it. Or we're just not asking the right questions. We tell them we need to have filters on now and they say we can't because it decreases the draw by 25%. Appreciate the answers, We're going to have to keep at them to come up with mods that we can filter it.

Yes, filters will increase static pressure and result in less flow. The way to overcome that is to add more filter area and/or use lower pressure drop filters. Which combination to use should not be hard to determine for someone who knows his stuff. They also should be able to address the icing issue.

John

Can you use any of the rolls of "cut to fit" filter media that you can sometimes buy at Home Depot/Lowes?

unless the air make up was junk to begin with which i doubt, most air make up are sized to have at least to handle a 1/4 to 3/8 worth of static pressure so even putting in a 1'' thick poly will not drop the airflow by 25percent

what about filters on the discharge area of the ductwork that comes into the building, you have more a of chANCE to overcome any static pressure issues as now this becomes a push pull system, air make up pushes, exhAUST FANS pull, i still believe you should have the check the amp draw, belts and motor rpm any one can make mistakes and i could save you a lot of time and these checks will not take a contractor a very long time to do maybe 15 minutes tops

good luck herbj

We have the HVAC contractor coming in this morning to discuss modifications. They build and design for large hospitals. I can't see why it would be a problem to modify ours.