Quote Originally Posted by breathe easy View Post
Frankly, I would go with the Honeywell media filter base. You can buy replacement filters in a MERV 11 which is probably all you need. These filters are easy to find, relatively inexpensive, have low pressure drop and should last about 6 months. No need for a pre-filter. They should capture somewhere around 95% of airborne allergens.

If allergens are a problem, you might also check my post on the "In search of better air" thread.

We are testing the HC16 now. The initial tests are right on the money. Very efficient and 0.31wg pressure drop. However, to achieve this they probably had to charge the heck out of the fibers which will neutralize in about a month. (meaning pressure drop will go up and efficiency will decrease dramatically) Efficiency has dropped from 85% at 0.3 microns to 79% in the first week. We have had to temporarily stop the test. Should start up again later this week. If it turns out OK, I will let you know. If you go with the Honeywell, you can always switch to the HC16 since the filters are the same size.
I am considering going to a non-electronic solution based a consumer reports article recommendation for the LENNOX HC16 (and by default HC10). Specifically: Honeywell F100, MERV 11 with a sp drop of .23. I think this is the one you are speaking of above.

Can you help me not with a particulate efficiency question, but with a question on resistance efficiency?

The static pressure drop on many electronic units ranges from .18 to .27. In the same range as some of these 4 or 5" thick non-electronic media filters.

How can I think of pressure drop when:
- eg my AHU/DUCT system measures .5 SP no filter in? ( I chose .5 as I read this is a max objective for sp on a system)
- filter sp rating is .25
- filter note says filter at .5
- the AHU operates up to .8 sp

So when filter is new, sp is starts at .5 + .25 = .75.
This looks to me like I only have .05 of static to raise before I have to replace the filter!!

Is it correct to think of this that way? Margin for loading the filter with particulates is way too low?
What am I missing?