We moved into a house with no filters on the furnace. so I put 1" MERV11 in intake grates, and last night the furnace stopped and the tech said I can not use these filters but to use the cheapest filter I can find.

I think this is a cop-out answer but I cannot find anywhere in Lennox literature the max MERV for this unit.

Can anyone help me with that

  • That surely is bad advice. It may be true that filters with a very high MERV rating may reduce flow too much, but the cheapest ones you can find are barely filters to begin with.
    – isherwood
    Nov 17 '20 at 20:42
  • Unfortunately, the manual merely states that "replacement filters must be rated for high velocity airflow". More on that
    – isherwood
    Nov 17 '20 at 20:46
  • Can you give us the height/width of the filter plenum in your setup? That's going to be the determining factor here... Nov 18 '20 at 0:09

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