HEAT PUMP FILTER OPTIONS? mervs and microns

[R J Cedar]

I am looking at putting in a heat pump in the basement that has a wood work shop in it.
The shop can be sealed off, and I do not use it that much, but I wonder about filter options, considering some wood dust escaping, since it is very bad for the coil in a heat pump. Warranty can become invalid. So gotta keep out wood dust.

Ok, seal off the workshop. Seal off the return air ducts.

Then if some wood dust did get into the furnace side of the basement, the only way the only way the wood dust can get to the coil is through the filter. The filter protects the coil, so what is the best filter considering these factors?:

WHAT TYPE OF FILTERS TO USE? Disposable or cleanable? Sounds at first like personal preference? I read somewhere that 50% of people want a disposable filter, 50% want a cleanable filter. Electrostatic filters block airflow too much, so go electronic cleanable or disposable media filter. But I wonder if the cleanable ones maintain a better flow capacity than the thick 5 1/2" disposable filter? The 1" thick standard disposable filters probably have the best flow through. Examine this in a minute.

WHAT MERV RATINGS AND MICRONS? Relate to function (what particle sizes to take out), their micron sizes and flow. Only info I have for flow is MERV but I understand there area other metrics like static pressure and CFM, but I don’t know how they relate to MERV.

I heard heat pumps are ok up to MERV 10. Then I got this after an inquiry to a filter manufacturer.

Eventually, all filters reach that 95% mark before they become completely clogged. The initial efficiency when you put the filter in is highest on our MERV 13. Anything higher than a MERV 13 is not recommended for residential HVAC units, because the high pressure can damage the motor of your unit. I would definitely recommend you discuss this with your HVAC professional. Here is a small chart from my desktop that will proved a little more info:

READERS...THIS CHART DID NOT COME OUT WELL, what is says is merv 12 - 13 = .3 to 1 microns for the first line of contaminants and particles.

The second line starting with auto emmisions is 1 to 3 microns and that is merv 10 to 12.

Mold, spores, household dust, sprays, dust mite debris is MERV 4 TO 8 = MICRONS 3 to 10. Etc. Sorry about the formatting here.

MERV Rating Size of Particles Contaminant and Particles

.30 to 1.0 All Bacteria Tobacco Smoke Fireplace Smoke Droplet w/Virus (sneeze) Smog Dust

13
13
12
12 1.0 to 3.0 Auto Emissions Dust Baking flour Pet Dander
11
10
10
3.0 to 10.0 Mold Spores Household Dusting Household sprays Hair Spray Dust Mite Debris
8
7
6
4
4 10.0 to 25.0 Pollen Dust Mites Sanding Dust Textile / Carpet Fibers
3
2
1

So go up to MERV 13 to get out down to .3 microns. Does the above statement mean that at the 95% mark of being fully clogged, there is still enough flow for the air handler?

I would think you need to change the filter earlier than 95%. How on earth do you tell flow rate required and when that is exceeded? Is there any simple device that would warn when airflow is too restricted - time to change the filter?

FILTRATON OPTIONS

Choices for me seem to be:

1. The air handler I am considering comes with a 1" rack. Could use a 1" disposable filter in it such as this:
American Air Filter Strata Density. DISPOSABLE MEDIA FILTER. 1"
The AAF StrateDensity data sheet gives no info on what microns are filtered out. No MERV rating, but maybe performance resistance data (cfm/inches water) indirectly covers off the MERV flow rating?
With some filters they tell you what % of particulates in a micron range they filter out…much better info, eg. 95% of .3 microns taken out.
.
2. $ American Standard AccuClean or Trane Clean Effects (same thing)
report down to .1 micron, but what is the MERV? Espically at 95% clogged?
Wood dust taken out over .3 microns at what %? Might be a good solution with a high capacity, but who knows? They work by first a prefilter, then second to electronically polarize particles with a negative charge then 3rd, to gather those -ve charged particles in a positively charged soda straw medium. Particles build up in the soda straws and you vacuum them out every 3 - ? 5 months.

3. High efficiency media retrofit air cleaner. Retrofit rack into the cold air return, just like the $1000 solutions, but with a 5 1/4" thick pleated media filter, no electronics.
E.g
http://www.westinghousehvac.com/Westinghouse-Media-Air-Cleaner-p/media.htm
removes airborne particles down to 0.3 micron.

I did wonder if the Trane Clean Effects or American Standard AccuClean would be a better option if I had a bit of wood dust around....these take out micron sizes down to .1 microns. But would they clog up more often or less often that the thick disposables? Which has the largest capacity to absorb volume, the 5 1/4" disposable, or the Trane/Am Std electronic, cleanable?

I would think the 1" would have the least capacity, but if it restricts airflow less, and still takes out the microns cost effectively, and costs less overall, this may be the best way to go. Simple may be best???

Would like to hear your perspectives, please. Thank you.

[beenthere]

Are you going to run the fan 24/7? If so, then a small supply register in the mechanical room (no return in the room) would create a positive pressure in that room, preventing wood dust from getting into it.

Will any of the return duct work be running through the wood shop area? If so, make sure its sealed.

I would think a 4 or 5" media air filter would be better.

[BaldLoonie]

I think the media air cleaner like the Westy in the link is the best value. Good pickup, far less restrictive than a 1" pleated.

I went to change our Aprilaire 20x25 which has been upgraded to the new MERV13 kit. The media was rather filthy. Just for fun I took a pressure drop over the media. Then I took a brand new 1" pleated and checked it. The new 1" was nearly twice as restrictive as the filthy Aprilaire. Personally I think the worst thing you can do to a system is use a 1" pleated.

When Big Dave put Sis's furnace in, he built in a slot in the return for a MERV8 Air Bear media. 12 years after the A/C was changed, we had to pull everything out to rebuild the plenum in the slab under it. That cooling coil was as clean as the day we put it in. Not 1 spec of dust on it. That Bear media, changed annually by me, sure did the job.

[R J Cedar]

Are you going to run the fan 24/7? If so, then a small supply register in the mechanical room (no return in the room) would create a positive pressure in that room, preventing wood dust from getting into it.

Will any of the return duct work be running through the wood shop area? If so, make sure its sealed.

I would think a 4 or 5" media air filter would be better.

Thanks for your reply.
run the fan 24/7, yes. ok, no return in mechanical room, but there would be one 10 feet away in a hall, where both the hall and the mechanical room are heated and together.

No return duct work running through the unheated wood shop area. Making sure the return air trunk in the heated area is sealed.

RE a small supply register in the mechanical room , what do you mean? supply from where to where? Is this the additional cold air return from the adjacent hall to the cold air return I plan to put in in addition to the existing 2 cold air returns from the main floor upstairs? Or something different? Or, I wondered if you meant from outside to the cold air return?

Thanks,
R

[R J Cedar]

Hello,
Thanks for your reply.

"I think the media air cleaner like the Westy in the link is the best value. Good pickup, far less restrictive than a 1" pleated. "

OK, don’t go to 1" and upgrade to a thick media filter. I guess with the initially expensive Trane/AmStd filters that you have to clean yourself, a compressor to really do a good job of cleaning would help. But with disposables you get a fresh start each time.

Thanks for confirming this Westinghouse 5 1/4 retrofit media approach is a good filter system, plus good value.

I do wonder how it compares to the Trion AIR BEAR choices you mention for airflow and cost. Is there any website or info cross comparing filters?

Throwaway or cleanable, I suppose it is the case that a dirty filter would cause issues with the operation of the heat pump if not dealt with when necessary. Is there any simple sensor device you can put on the unit to tell you when the airflow is restricted too much - time change the filter? Or is practice just to keep an eye on it?
Thanks!

[beenthere]

Supply would be from the supply duct/plenum to blow air into the mechanical room.

[R J Cedar]

Supply would be from the supply duct/plenum to blow air into the mechanical room.

I understand, then yes, the mechanical room is heated with 2 outlets. Flow to cold air room will be in the adjacent hall, the other way from the wood working area, and positive pressure in the machanical room. thanks

[R J Cedar]

In comparing MERV 11 disposable pleated media fliters across manufacturers, what measures can I use?

MERV relates just to what particles are removed.

For the resistance rating how is this measured?

Is there any measure for adsorbption capacity?

Any other measures?

Thanks