(Sold by contractors that want to sell you new hvac equipment)
For standard residential hvac units, if your system is designed for standard filters and you use these high MERV filters, you can destroy the equipment. It’s more expensive, so they won’t be designed for this unless you ask. If you want to clean your air without risking destroying your hvac unit’s refrigeration cycle, buy a separate air cleaner and put it near the return. You will also lose heating and cooling capacity because the airflow will drop. It will also use more energy to heat and cool your house, because it will require longer run times. Only use these if the system is designed for it, or you have relatively forceful air flowing from your diffusers.
Source: hvac engineer
Thanks a lot for the info!
As an aside, what do HVAC engineers think about washable air filters?
Great money saver or dangerous mold incubator?
As someone who just recently replaced his entire system due to a cracked heat exchanger, I can’t agree more enthusiastically. I always used the expensive Filtrete Elite Allergen filters. Apparently they restrict the airflow so much that the system wasn’t moving enough air to dissipate the heat in my heat exchanger.
Now I stick with a much cheaper Flander’s Pre-Pleat 40 (Merv 8) filter in the new system, and 5" filter media box in the return just before it enters the furnace.
I’m always torn by these since my girlfriend has horrible allergies (and we have a beagle) but the whole increased power consumption and HVAC damage stuff is bit concerning.
I do mostly commercial work and I wouldn’t specify them in most places, but there is one system we use washable filters in all the time. Those Mitsubishi mr slim units; their filters have anti microbial treatments. It really depends on your space. If the filters start out mold free, and are dried properly after cleaning, I don’t see it being a problem. I expect thre are plenty of non-toxic cleaners to get that mold off. Of course, if conditions are ripe for mold growth In the house, such as no sunlight and letting the house setback to very high temps when are away, it certainly won’t prevent it. If you can stand a little extra maintenance and want to mitigate mold problems, you can install a UV light in the return. Best location for those is actually inside the equipment, shining on the cooling coil, but any where in the return duct will help.
Thanks, almost bought them. I will keep using what I have been buying. Knowing nothing about filters, these looked like a great deal.
I purached a set and found they were smaller by about a half inch than the ones form the store. I was able to use them by modifying the filter area
Woot Staff: please provide the manufacturer’s air pressure drop data, your California homeowners will need that info. The data should appear on the product packaging.
The new California 2013 Building Energy Efficiency Standards sets minimum air filter performance standards (new systems now have to be designed to handle at least MERV 6 filters) and requires the home builder label the HVAC system for what the maximum allowable clean air filter pressure drop can be. The label is usually found near or behind the furnace air filter.
The air filter requirements appear in Section 150.0(m)12, on pages 222-223.
Folks not living in California could also use that same filter data to compare these filters with their current filters to judge if they can use these without increasing their blower fan speed.