I'm defenitely way past the point where I have to replace my filter.

The size and shape of the filter is, obviously, something that needs to be the same as the old filter, but except that, is there any other things that are absolutely needed to be the same or the rest of the attributes of the filter may vary and are basically, personal preference?

Basically, there are types, if I take the wrong one, could I damage or hurt my heating system?

Also, my filter seems to be 3 3/4 in thick, but all I see is 4in thick... is the size just rounded?

1 Answer 1


The MERV/FPR rating gives you an idea of the flowrate vs filtering capacity of the filter. If you use a filter that is too restrictive for your furnace you will stress the blower, but since you have a 4" filter most have adequate airflow for most furnaces. Unless you have a specific need stick to a moderate MERV rating replacement filter or lower

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