Packaged Unit - MidDay Failures

[Fett]

Hello guys, I have a 2-ton Goodman that is 2 years old. I have not had much time to really work on any units because the facility I work at has new equipment. Although this particular unit fails during the hottest portion of the day.

Example: The unit operates correctly at night and during the morning hours when the temperature is below 105degrees F. Any day that we have had above 105degrees F the unit shuts off mid day between noon and 3pm and remains off till 5 to 7.

It is a heat pump and the refrigerant is R22. Superheat is low 3-6 degrees, sub-cooling is high 13-18 degrees. Low side pressure after 1 minute of unit operation is 70psig and rises very slowly to 85psig after 15 minutes of operation (at 111degrees F). High side pressure acts the same with 270psig and rises to 310psig (at 111degrees F). The unit has a copeland scroll compressor. Condenser and Evap fan operate. This unit also mixes 30% outside air with inside air. When the unit shuts off the evaporator fan runs for another 5 minutes then shuts off resulting in hot air blowing into the conditioned space.

What do you guys think? I'm leaning towards overcharge.

[Magoo]

Hi Fett.
tend to agree with the overcharge idea, as well the 30% fresh air mix would be loading system up something terrible try reducing to 10% for peak summer loads.

[Fett]

Hi Fett.
tend to agree with the overcharge idea, as well the 30% fresh air mix would be loading system up something terrible try reducing to 10% for peak summer loads.

I would love to reduce the fresh air intake although for commercial buildings here in Phoenix (our air quality is horrid) 20% is mandatory. This unit cools a small enclosed office space in our facility and just outside is a industrial battery charging station. The charging of these batteries puts off fumes and it would really suck to get a random inspection and fail it because I changed the fresh air intake.

Are there any other symptons I should look for to determine if the charge is improper?

[nike123]

What is metering device type?
Give us indoor WB temperature, outdoor DB, superheat and subcooling and pressures at that temperatures when unit work for more than 20 min.

[Magoo]

Hi Fett.
try decanting some liquid out of receiver/high side and reduce the subcooling from the condenser. Could have been overcharged during cooler ambients.
With the fresh air make up, lower it to 20% and add a swamp box cooler pad system to knock some sensible heat out of air as well will soak up fumes as well.