system stops cooling once a day

[karsthuntr]

Originally posted by cjj
It has a self reseting high pressure switch and two liquid line dryers on it

See if your losing voltage from the high pressure switch. And remove one of those dryers. Check the temp drop across the dryer also.

[jchaters]

I do not know if this is your problem but I have found that in certain areas of Toronto, we are having low voltage problems during the hottest part of the days due to brown out problems. The 220 voltage is dropping off. It is only in older parts of the city as they have older electric system. Has anyone else run into this?

[mark beiser]

Originally posted by cjj
It has a self reseting high pressure switch and two liquid line dryers on it

My money would be on my origonal theory.
Clogged liquid line filter drier inside the unit before the service port, system overcharged, and High pressure switch tripping, especially when it is hot and the off time for the unit is shorter.

Most of the time, there will be no temperature drop accross a partially clogged liquid line filter drier unless it is severely clogged.

I just had a call on a York unit monday that had a scroll compressor someone replaced and left the factory liquid line filter drier in.
It was partially clogged, and the system was overcharged by about 20%.
Sometimes when it started up, the discharge tubing and condensor coil would vibrate violently for about 20 seconds because so much liquid was backed up into the coil that there wasn't enough volume left for the refrigerant vapor to condense. The pressure in the condensor was spiking up almost high enough to trip the compressors internal overload. If the system had a high pressure switch before the factory filter drier, it would have been tripping.
The high and low side pressures, sub cooling and superheat were all dead on the money with what they should have been.
It was fooling me for a while because I couldn't reliably reproduce the sound.
When it finally did it, I happened to be watching my amp meter that was clamped on the common lead to the compressor. The amps would spike up over the compressors RLA when it did it, but the compressor kept running smooth as could be. I also recognized the sound. It sounded exactly like what the indoor coil on a heat pump does in the heating mode when the indoor coil is badly undersized for the outdoor unit, so there isn't enough coil volume to condense the refrigerant.

[kempdawg34]

Any chance that you have a moisture switch or a secoundary drip pan float switch? If so that will mess up things

[cjj]

I replaced the T stat in the house and moved it from under the return vent and the unit did not short cycle It ran all day no problems as for pressures well 60 0n the low side 195 on the high 8 sub cooling as for the filters no temp drop across any of them who ever changed the comp never took out the facture filter and just added another I guess my next thing to do will take out both filters and and a new !!!

[robnjr]

I don't get it. If it was the thermostat, a few simple meter readings should have shown that it was switching the contactor OFF. Maybe you have more than one problem......