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.
20 x 20 is too small. You need a larger return to reduce the velocity and the noise.
The notion of "too much" airflow is incorrect.
Your evaporator blower motor, and wheel, only has the capacity to move a given amount of air.
It can't pull TOO much. You could put in a 36X36 return grille, and the unit would only pull up to it's maximum potential.
Some cheap return grilles are notorious for making noise.
If you wish to maintain that size, you have 2 options. Change the FB Grille to an "eggcrate" style, which has a much lower restriction, or add a small remote return to another part of the home.
There are other details involved to be able to tell you exactly what to do.