Air Filter question(s)

[TConnors]

It's been a while... I still see many familiar names. I've been using Honeywell 4x20x25 Merv 10 filters (FC100A1037) for a while and started searching for a new source. I noticed Home Depot carries a Merv 12 "CF200A1016" at a good price. I can't find and technical data anywhere. It's probably more restrictive than their Merv 10, but would be nice to know how much more. Anyone recommend these?

My second question is I have 2 ceiling returns, with with 1" filter frames. I currently don't use filters in them (only the 4" at the AH). Is it wise to use cheap pre-filters to keep ducts clean? I'm thinking it's just adding to air resistance and not worth it.

[Rhino32713]

i found this on Home Depot web site hope it helps.

The Honeywell 20 in. x 25 in. x 4 in. Pleated FRP 10 Air Filter is up to 60 times more efficient than a standard 1 in. furnace filter. It helps keep your home or office free of dangerous pollutants for up to 12 months by filtering dust, pollen, mold, smoke, bacteria and viruses.

Filter Performance Rating (FRP) of 10 provides protection against smoke and microscopic pollutants
Pleated filter with a Minimum Efficiency Reporting Value (MERV) rating of 12 captures a high percentage of household air particles, including those at 0.3 micron which are most harmful to your lungs
Lasts up to 12 months
Purifies air by catching dust, pollen, mold, smoke, bacteria and viruses
Also fits Aprilaire and Space-guard models 2200 and 2250
Easy to install

Assembled Depth (in.) : 18.80 in
Assembled Height (in.) : 23.40 in
Assembled Width (in.) : 4.30 in
Electrostatic : No
Filter Frame Material : Cardboard
Filter Material : Polypropylene
Filter Performance Rating (FPR) : 10
Filters Bacteria : Yes
Filters Dust : Yes
Filters Mold : Yes
Filters Pollen : Yes
Filters Smoke : Yes
Filters Viruses : Yes
Fully Incinerable : Yes
Item Package Type : Bag
Item Weight : 2.25 lb
MERV Rating (Minimum Efficiency Reporting Value) : 12
Manufacturer Warranty : na
Nominal Height : 25 in
Nominal Thickness : 4 in
Nominal Width : 20 in
Pleated : Yes
Product Height (in.) : 25
Product Thickness (in.) : 4 in
Product Width (in.) : 20
Removes odors : Yes
Returnable : 90-Day
Trimmable : No
Washable/Reusable : No

[GAC]

My second question is I have 2 ceiling returns, with with 1" filter frames. I currently don't use filters in them (only the 4" at the AH). Is it wise to use cheap pre-filters to keep ducts clean? I'm thinking it's just adding to air resistance and not worth it.

If your duct system is good, then it would be better to just use the filter at the AH. You're right, using the filter grilles will increase your static pressure. If the static gets too high, and you don't have an ECM blower motor, this could cause high amp draw and premature wear on the motor.

[TConnors]

I saw that info Rhino.... not sure about that "assembled height and depth", doesn't seem to jive, pretty sure it's 25" x 20" (or slightly less), that's easy to measure. None of the other numbers "FPR" or "MERV" really tell you anything about air flow. I figure if it's Honeywell, it's probably the same media they use in most of their other filters.

The specs on the FC100A1037 are:
Minimum Efficiency Reporting Value (Media Filters Only) MERV 10
Static Pressure Drop (in. w.c.) 0.23 at 500 FPM

[HeatXfer]

Rhino32713:

Please don't cut-n-paste Google searches, it's like that joke about teaching pigs to sing.

Anyway, the closer a filter is to the fan intake, the cleaner your system will be; less return duct infiltration between the fan & the filter.

merv 10 & 12s are rated at same 'arrestance' of >95%. What's called dust spot efficiency is about 50% for the 10 and 75% for the 12. You probably won't notice a difference unless all the dust in your area is no smaller than 1 - 3pm.

It's better to change the air filter based on pressure drop rather than the "it looks dirty" method. The less often you change your filter, the cleaner your system stays: The dirtier filters get, the more efficient they get - to a point: don't let them go too long.

[TConnors]

Had a gauge at my old house, need to go out and get another. What's a good limit (for filter change) for a 4 Ton Carrier AH? Maybe 1.0"?

[HeatXfer]

A 4ton air handler will move about 1600cfm; through a 20"x25" filter that's about 460fpm. PD for a new merv 10 is about .23" to .25"wc at approx 480fpm. Typical recommended pd change point is .75" to 1.0" above the new pd. So anywhere from 1.0" to 1.25"wc is fine - you're right on the money.