Air blowing at air handler

How much air leakage is aceptable at air handlers? I run into this about a third of the time. The air is usually coming out where the return plenum and combustion plenum joint. The other day, quite a bit was blowing out from the combustion plenum only. When is it too much?

If you can feel it just standing next to the unit, it is to much for me. It is an easy fix, just write it up.


The units are supposed to be sealed. There should be no air loss. Write it up.

I see air loss at the refrigerant lines quite a bit (line entrance is unsealed). I write it up.


What do you mean by combustion plenum?

The supply (S/A) plenum on top of the furnace would provide an outward flow toward you and a return (R/A) plenum, typically on the side would develop an inward flow or negative flow. There should be no are leaks. Recommended fix is either a fire rated mastic or silver/foil tape. This would be applicable for all fuel systems (ie: Nat.,LP, Oil, Elec./Ht.Pump, etc.).