HVAC maintenance log
PM visits, filters, coils, belts and repairs against the unit they happened to.
Filter changes, coil cleans, belts, refrigerant work and repairs against the unit they happened to — using the equipment list you already keep, not a second one. Parts and filter sizes where you want them, and the next visit date is the one you agreed with your contractor.
Service history against the equipment you already have in the asset registry — no second HVAC list. Filter sizes and next-visit dates are the ones you enter; nothing here decides how often a unit is due.