filter changing

[agross]

I just started my first HVAC job a few months ago at the STL Zoo; a bunch of different equipment, Residential Split Systems, RTU's, Chillers, ect. Anyway, went to PM the penguin building, a very critical building, obviously. Two 180 ton York Chillers feeding Temptrol(Spelling?) AHU's. On the each of the AHU's there are gauges showing pressure drop across the filters. Today they were showing about .4 inches of water column. At what value would you change the filters? I opened the doors, and they didn't look too bad, they were dated 7/29, so it hasn't even been a month since they were changed. Thanks for the help, Adam.

[prestiege]

i cant remember what we changed are filters in a hotel i used to work, in critical systems i would say going by the water column is better, the chief at the hotel wasnt very helpful at times allthough he knew a lot, i tink he looked at as if i wanted to know to find out on my own, he just told me to change them once a month thats the way weve been doing for the last 10 years

[umd]

Generally speaking, keep pressure drop across filters at less than 1.0 inch of water column...

[fused]

A good rule of thumb is to record the initial clean filter pressure drop, then change when the drop doubles. Most pre-filter manufacturers do limit maximum drop to less than 1" WG total, as umd has stated. HEPA filters are another story.

[Edited by fused on 08-20-2004 at 09:47 AM]