Forced air HVAC for dust control?

[Rob Will]

In Phil Thien's excellent ongoing thread about measuring shop air quality, the question came up about using a forced air furnace to clean shop air. This is something that I would like to discuss further but I don't want to hijack Phil's thread so here's a new one.

Al Willits brings up a very good point in the other thread:

"Just a note for those of you who think your furnace is supposed to keep your air clean too, be careful, as furnace filters were designed to keep furnaces clean...period.

Furnace & A/C units are designed to work with a certain air flow, the company I work for makes a tidy profit from replacing heat exchangers and A/C units from units being misused with too restrictive a filter.

Make sure your filters will pass the required amount of air."

Al[/quote]


Thanks for the reminder Al.
Just to be sure, I may install an extra Dwyer gauge on the filter plenum.
What would be a typical negative pressure (inches of H2O) between the filters and blower?.... 0.1"? .... 0.5"?

I really like using my HVAC for air cleaning and will do whatever it takes to protect the furnace (Lennox Pulse furnace 80K BTU / 3 ton AC). This includes installing multiple filters.

Anybody had any experiences (good or bad) with using the HVAC for dust control?

BTW: That particulate counting meter in Phil's thread sure looks interesting:cool:.
http://www.sawmillcreek.org/showthread.php?t=73486

Thanks for your input,
Rob

[Phil Thien]

Also a great thread. My electronic air cleaner probably has a somewhat less restrictive airflow than those using pleated filters. But, I do have to keep it clean to keep the efficiency up. I clean it every couple of weeks, which may be more often than required, but I run it 24/7.

I find the little hand-held anemometers (like the ones made by Kestrel) handy for testing this kind of stuff. If you are concerned you could measure the MPH at your vents using a few different filter configurations, to make sure you aren't starving your furnace.

[Dave Mapes]

I must be missing here.

I don't know about your home heating system; but my system sucks air out of the house, down into the filter system then down into the heat/AC and back into the house. It would seem to me that with that type of system there would be nothing to filter any air that is extracted out of area near your furnace.

So using a furnace to clean your air would not prevent shop dust from entering the air system when the shop is located near by.

[Rob Will]

I must be missing here.

I don't know about your home heating system; but my system sucks air out of the house, down into the filter system then down into the heat/AC and back into the house. It would seem to me that with that type of system there would be nothing to filter any air that is extracted out of area near your furnace.

So using a furnace to clean your air would not prevent shop dust from entering the air system when the shop is located near by.

Hi Dave, My shop is a separate building with it's own forced air system.
There is no duct on the return. There is a SpaceGuard pleated media filter at the furnace and a pre-filter box attached to that. Basically the return goes directly into the furnace.

I agree with you, we would not want to use an open return for dust control - it should be filtered at the intake. I'm not really familiar with a shop in the house that - shares a HVAC system(?). Others know more about this than I.

Rob