The installer says that the fan speed in this dual-stage system is set
by
the factory and cannot be lowered. It's a Rheem 80% 2-stage Criterion Two+,
Model RGPK 70.


Sounds like BS to me. A pleated filter would lower air flow 10 to 20
percent. Try that. The fan speed IS set by the factory. It may
already be set to the lowest speed tap, but probvably not. Most likely
your installer is looking for an easy way out. Did he actually MEASURE
the air flow when he installed the system? He should have.


Stretch