Arghhh don't ya just hate when this happens.
Was working on an AC unit at a Huddle House.
Checked the unit from head to toe and couldnt' find anything wrong with it.
Pressures, superheat, subcool, amperages, CFM.... everything... right on the money.
But why for it not cool?
The dad blame fresh air for the vent a hood.
It wasn't adding enough fresh air for the hood and made the building go into a vacuum pulling in hot air from every nook and cranny.
Nice breeze coming in the door when ya crack it.
The kitchen hood exhaust might be pulling too much also.
but unless you can verify your maintaining minimum required fpm in exhaust duct you may cause a fire hazard by slowing it down.
Good point Islander.
Also check to see if the RTUís have minimum outside air dampers. Usually set to 20%.
My rule of thumb may not be right for you but here it is
100 CFM of outside air x # of A/C tons = good exhaust make up
(*if the exhaust fans are properly sized and there is NOT a make up air hood)
Use the olíNapkin test. Open the rear door and see if a limp napkin pulls in or blows out.
Out = Positive
In = Negative
Much rather be a POSITIVE person than a grumpy olí man.
Is there a make-up air unit? Almost all kitchen hood I have worked on have air blowing in on the frontside and exhaust on the backside. Look on the roof for that make-up air fan maybe plugged filters.
I cut my teeth on restaurant work; even the food service equipment. I still can't open the door of a restaurant without my face by the door to feel if the building is on a positive or negative. Most (especially the older they get are on a negative). Also can't drink my drink without first determining what brand icemaker made the ice. I'm a sick man.
That and the A/C unit is marginally sized......to say the least.