S.O.B.

[bicod]

Have an 8 1/2 ton york preditor roof top. On hot humid days late in the afternoon the unit fails to maintain temp. and raises to 75-76 from 72. Have had tech in to check but they always seem to show up when it is working fine. Unit is not icying up fans are running fine and no code flashing to indicate a problem.
Any suggestions?

Thank you
Bicod

[jim_long]

Check the inlet side of the evaporator coil (cooling coil) with a flash light to see if you can see through it easley. These coils will become partially plugged over time and will not transfer heat properly. Also, if this is an older center that was around during the "Smoking Years", you may have tar build up on the coil fins that reduces heat transfer.


Try giving the coil a good blow down with compressed air, then a good cleaning with a commercial coil cleaner and finally a good rinse.

[rivmike]

I had one that at sun down(outside air cooler than inside) the economizer would shut down the compressor. (we had closed them off and thought they did'nt work, 1973 unit) The other thing I just found was the cold air return spout was 16 inch. above the ceiling tiles, thus sucking alot from the lanes but some from the extreme heat up by the roof. My newest unit is in the added 12 lanes and has no spout, It sucks right from the roof. (that's getting fixed!)

[Pietenpol]

I'm dealing with a/c issues as well. Got a rotted condensate pan that has a tendency to drip down the ducting after running for an extended time. For your issue I agree with Jim, coils clean? Fin brush isn't expensive at all.

[Ted]

Air movement is key. But coolant gages and temperature of the suction line will tell you if there is enough refrigerant. There could be things as run capacitors and their connections that will effect maximum efficiency. Multiple units and where their controllers are positioned make a huge difference, but the initial design/position should have been made with the utmost efficiency. But second opinions are much like ones for medical conditions.

[JACKO]

Lot of great responses, sounds like unit is a little newer, since flashing diagnostic board. Is unit new? Does this unit take care of bowling portion, or other area? 8 1/2 ton is not that large of unit. Could be to small for job? Cleaning is always a must for longevity and efficiency. This summer has been extra tough though! If cleaning doesn't help, well atleast it will be clean. It would be great to hear what resolves your issue, as there is alot to be learned from this expierence, and for future troubleshooting. Thanks! Maybe on your own, try monitoring discharge air temp at supply vents, throughout the day,to see if deviates much!

[bicod]

The unit is not that old, it has been doing this since it was new. Hot weather with lower humidity the unit runs fine. Will double check all the above tips and advise.

Thank you
Bicod

[jbl]

Was wondering if the unit was not sized right for the capacity you need to cool the building and that you need more evaporator coil capacity.


As the humidity increases. More of the A/C's heat removing ability is used to remove the moisture from the air(condense it). And less to cooling the air temp.

Once the humidity is lower. Some of that capacity that was being used to remove moisture from the air, will be switched back to lowering the air temp.