Originally Posted by angus99
Got a balky A/C unit cooling this morning — just in time for the end of the heat wave. A guy helping me saw the thick mesh filter material the PO had left on the boat and said it restricted airflow too much. This material is cut to size, held in place by brackets on the inside of the return air grill and needs enough rigidity not deform and get sucked into the unit.
Most of what I see online looks like flimsy foam or stuff that looks as restrictive as what I already have. What do others use for return air filters?
Your suspicion is more correct than not. Your filter media appears to be Duralast, it's available in rolls, and is very handy to cut to size. In my time in the HVAC service trade we usually kept a partial roll on each truck. It's better than throw away fiberglass filters, it can be sprayed with cleaner like simple green, hosed off and put back in service. It really doesn't need to be bone dry, the air moving across the media will quickly dry it. The 1/4" foam is more restrictive and can block with just a light coating of particulates. Pet dander is particularly hard on filters. Just as a point of reference for your larger home filters, pleated filters offer less resistance. Resistance translates into reduced air flow that drops the efficiency of the system and can cause the evap coil to freeze. If you have that happening, you need to get more air flow either by juicing up the fan speed, cleaning the fan & coil, or changing the filter more frequently & perhaps to a less restrictive media- like the Duralast. The filter's job is to protect the coil and fan from accumulation of airborne dust, it's not intended to clean the air you breathe. Those "high efficiency HEPA" filters and the like are typically pretty restrictive. Homeowners think they're making a big improvement in their air quality when the more significant impact is they're adding unnecessary restriction to their system and dropping the efficiency. If you really want to make an improvment in the air quality, you need to look into electrostatic air cleaners. Not cheap, but very minimal resistance and most effective particulate removal in the micron range.
You can prove it, clean the filter. Re-install. Run unit to get it settled out, then check the splits (entering vs leaving air temps). Record. Remove the filter, repeat. Compare results. If the split is higher with filter, it's restricting. Couple of degrees isn't a problem, but it will demonstrate if it's restricting. Filter efficiency increases as it gets dirty to where it's 100% efficient. But then NOTHING goes past, even air.