Fan speed controller for a fan coil unit

Hello I have a 2 fan heat exchanger coil unit . Similar if not the same as the kind you'll find in a walk in refrigerator.

I have a fan speed dial controller I'd like to use to slow down the fans on the coil unit to make the fans quieter . I tested it and it does work to what I was looking for . Is this ok for safety ?
The motor is a : Fasco 1/15hp , 1550rpm , 2.1A , model : JA2R258N#
I tried researching to see if the Motor was brushless or not . . .

freezer fan coils are usually simple PSC motors.

have you tried just shutting down one motor?

you can replace the motors with ECM motors+ a control board... that will save you some electricity... but recall these things are like 1/6hp each max, and they will never pay for themselves even at that larger size.

speed controlling PSC motors is problematic to say the least... you would be better off building a damper onto the suction of the fan coil. these cheap controllers often cause the windings to over heat as the amps jump in proportion with the voltage chopped off the tops of the peaks. also because the fans rely on their own air flow to cool themselves... the extra heating is further exacerbated by a drop in air flow across the motors.

all that being said, if your particular speed controller is doing what you want... and the motors are not buzzing or getting hot, then fine... what ever you are good. will they wear out faster? maby, but maby not its not really possible to say. these motors are pretty cheap though, so who cares either way.

regarding the damper.
yes this will require sheet metal work... but i cannot really give you another solution that would not require replacing the motors.

yes putting a damper on the intake will make the motors louder... how much, i cant say...but the actual amp draw will be less, and the torque and HP figures will be less ( you can verify this with a clamp on ohm meter).

Thanks for your detailed response . I will run this all day and check the motors periodically to see how hot they get .

I have a lot of water cooling equipment I am not using anymore so I decided for fall and winter I would try something else so I can keep the room sealed with AC.

The fan coil is gonna be in my shed as my ambient chiller that's why I want less noise for stealth . Water lines already buried going to and from