Performed semiannual maintenance on one heat pump heating system. Inspected all Performance, Mechanical and Safety Systems. I found that the April Aire 4” Media Filter was extremely clogged up creating an inflow restriction across the indoor coil. They had a new filter on-site, so I changed it out. Tested the refrigerant system and verified the system was operating with a 10° subcooling value and had the proper heat transfer across both indoor and outdoor coils. Verified everything was operating within manufacture’s specifications for operation. Everything is working at this time. See attached checklist for full tune-up details.