[360]

Tried to use search function as I’m not seeing it.  Is there a particular filter material everyone likes?

Found a roll of MERV 8 on Amazon.

[hypoxia]

I don't have SCS however in the A/C furnace filter department I have an opinion.  Some newer HVAC systems are made to accommodate more filtration up to HEPA but most are not.  I use either the cheap dollar filters or the reusable filters.  The idea is to filter out the larger particles and let the small ones pass through the coil.  Anything more restrictive increases the compressor pressure and makes the system work harder.  The end result is less reliability.  The older systems with copper coils and R22 were reliable and could take more abuse but the newer R410 systems with aluminum coils are very problematic.  The pressures are much higher and the aluminum is prone to cracks.  Reusable Filter

[360]

I don't have SCS however in the A/C furnace filter department I have an opinion.  Some newer HVAC systems are made to accommodate more filtration up to HEPA but most are not.  I use either the cheap dollar filters or the reusable filters.  The idea is to filter out the larger particles and let the small ones pass through the coil.  Anything more restrictive increases the compressor pressure and makes the system work harder.  The end result is less reliability.  The older systems with copper coils and R22 were reliable and could take more abuse but the newer R410 systems with aluminum coils are very problematic.  The pressures are much higher and the aluminum is prone to cracks.  Reusable Filter

Thanks Jim for the advice.  I'm moving into a larger storage bay this fall so I'm also planning to have someone come over and help me slide the units out before spring and give the coils a good cleaning as well.  Sounds like on something this old that air flow and keeping them clean is the key to success.