Just had a new heat pump system installed 13 seer 3 ton unit. The issue I'm having is the return is howling (as opposed to whistling). When I lower the grill so only the filter is exposed, it's nice and quiet and of course this is my goal. The return is 20" x 20" so I'm thinking of possibly changing the grill out. However, being completely ignorant of HVAC, I don't know if this would be detremental to the system. I've read that too much air flow could shorten the life of the handler and I suspect in order to eliminate the howl, the airflow would be increased. If you have any guidance, suggestions or meaningful insights, I would be most apprecative.