I have a 4-ton ducted heat pump that runs year around. It has two returns sized at 14x14 and 14x30. I'm using 4" MERV 11 filters changed at 30 days/720 hours of run time. I just changed them and while they certainly have some dust and the new filters make less noise than the old, they don't look that dirty. I have the unit serviced every Spring and the tech always says the coils were clean.
Is there a rule of thumb as far as run time and filter size? I do have a cat and dog and there are five people living here. I'm happy to spend the money if needed but these filters are getting hard to find with lots of places out of stock and they're not cheap.
Is there a rule of thumb as far as run time and filter size? I do have a cat and dog and there are five people living here. I'm happy to spend the money if needed but these filters are getting hard to find with lots of places out of stock and they're not cheap.