Have the check the fire dampner if the building is new and has no airflow even when on high.
These are idividual units itsounds like. I don't thinlk you need dampers unless the ducts penetrate the wall to another apartment unit.
Correct me if I am wrong.
If it is set up that way then yeah that is possible.
It has been my experience with high rise buildings that new that the workers had to run the heat to dry wall the place.
The fact the maintenance man pulled the filter in a "Brand new building"
tells me the filter was jammed packed with dirt.
The unit is individual to the apartment. It is mounted in the ceiling, and blows through ducts into three rooms, the living ares, and two bed rooms. The ducts to the bed rooms have to be about 1 to 2 feet long each, and the one to the living area maybe 5 feet long. The access panel over the unit swings down and usually holds the filter. I have been in the apartment 10 days and there was no filter in the unit when I moved in, I did request to have one put in the day I arrived. The maintenance guy (construction coordinator) said he would once they had it fixed, even to my objections.
Thanks for all the feedback and ideas guys, I really appreciate your help! I should be able to formulate a good argument with him to get a professional to come and really work on the unit.
On the other hand if you have a flow controlled system where you have feedback control to hold the flowrrate constant then the opposite is true.
The OP's system does not have this control.
It is either a bad design on the part of the mfg, or a bad (batch) of motors, or low voltage, or a bad cap or some combination of these. Also as was said, any HVAC motor is certainly rated for 100% duty cycle.
Going by the OP, this sounds like a fan coil unit, running chilled water from a centralized chiller. If the apartment is not on a top floor or has a lot of glass/wall area exposed to the sun, it should stay pretty darn cool in there with a chilled water fan coil set on 68.
Motor going out on overload...replacement motor possibly wired incorrectly, incorrect voltage, or run capacitor bad (brought over from original motor, maybe, or new one bad out of box).
The on-site guy handed you a load. Those motors in those fan coils can run and run without overheating if they're wired and sized correctly.
Weak airflow when the blower manages to run is why you're not getting your apartment down to 68. I'd put money on the cooling coil being plugged with drywall dust, as others have said. The original motor windings may have been plugged with dust as well, which is why it failed.
Running the unit without a filter in it is just asking for trouble.
The motor speeding up in a canister vac by blocking air flow also causes motor over heating.