Air filters and Max MPR (High-Efficiency Heat Pump) (furnace, Air Conditioner, installed)

[Mike From NIU]

I saw that this topic was covered briefly in the past. However, the general advice (use the cheap blue filters) won't work for my 3 year-old HVAC system. Cheap blue filters buckle and start to get sucked into the fan area. They don't go far enough into the system to do damage or get hit by the fan, but they definitely no longer filter the air.

I've found that 3M's Filtrete filters have a stronger frame that holds up to the suction of my fan. Thus far I've used the baseline Filtrete filter (300 MPR). I am thinking of moving up to the 600 MPR version that promises better lint and dust mite debris filtration, as those two items are definitely present in my house and we have allergies.

I've read in multiple forums that the extremely thick MPR filters decrease efficiency of the HVAC units and can shorten the life of the blower. However, at what point does this really start to occur? I would assume that the 1500/1900/2200 etc. MPRs would significantly affect air flow. However, is there a significant between 300 and 600 MPR?

If it makes a difference, an Amazon review relays the following data that purportedly comes from 3M:

Dust & Pollen 600:
1-10 microns - 70%
MERV 8
pressure drop .14

Dust Reduction 300:
1-10 microns - 60%
MERV 7
pressure drop .15

I wouldn't go higher than 600 MPR, but wanted some other people's input before even moving up to this level.

Thanks for your help!

[HWTechGuy]

I use Filtrete 1085 (red) filters with my dual-zone heat pumps. The system is approximately 6 years old and has 1" thick filters at each return. Each system covers half of the house and each has 4 returns, one 18" x 24" in the common areas and three 12" x 12" in the bedrooms. So, far I am having no problems but I have only been here a year and have only changed the filters twice. Previous owner had the cheap blue filters in place which were seriously overdue for a change when I bought the house.

My old house also had dual-zone heat pumps but only had a single filter right at the air handler for each unit. I used the Filtrete 600's when we lived there and changed them religiously every 90 days. I tried using the Filtrete 1200 filters because (against my wishes) my mother-in-law smoked in my house. But the one unit started to ice up due to lack of airflow, so the HVAC guy told me not to go higher than the 600 filter and change them regularly.

[MrRational]

Originally Posted by Mike From NIU

the general advice (use the cheap blue filters) won't work for my 3 year-old HVAC system.
Cheap blue filters buckle and start to get sucked into the fan area.

Sounds like the fan is running wayyyy fast.
You should check on that.

[Pink Jazz]

Most modern residential systems are designed for a maximum MERV rating of 8 (MPR 600 in the 3M Filtrete system). The advice to use the cheap fiberglass filters is a myth for the newest systems, since they are ineffective at protecting the coils in the air handler or furnace from dust or other dirt. We use MERV 8 filters and they work just fine for our system (we recently had our air conditioner serviced and the tech said our filters were fine).

While you may get some initial energy savings from the cheap fiberglass filters, allowing more dirt to reach the coils by using them will negate those energy savings in the long run and cause potential damage to your system.

At the same time, if you want a MERV rating higher than 8, Honeywell offers several deep pleat filters with a lip that allows them to be installed in a standard return air register. The deep pleat filters have more surface area, which increases airflow.