oversized condensing unit

[taylortech]

Working on a med temp W/I cooler 6x6 the condensing unit is rated for 10,000 btu @35f box temp r-22 txv system.I know that it is way oversized but is there a way I can adjust txv to compensate untill this problem is resolved the correct way? thanks

[icemeister]

As long as the evaporator capacity is matched up with the condensing unit capacity there should be no problem at all. The size of the box is almost irrelevant with respect to system operation. My only concern might be rapid cycling which is easily compensated for.

Don't go messing around with the TXV. All it knows how to do is to maintain a relatively constant suction superheat by metering the refrigerant flow to the evaporator.

[taylortech]

Ice thanks for the reply. Your exactly right it is short cycling and T-stat does not have time to react quick enough to rapid changing temps. Control is in evap, tried moving to sense air N.G. Do you think switching to a control with tighter diff would help? Right now at max setting box cycles off at 30 and on at 42.

[icemeister]

From the CO/CI temps you posted it looks like the t'stat is stuck in the coil sensing evap temperature. To increase the run cycle time, lower your CO. The CI should be somewhere close to the desired box temp......42ºF is a bit high for food storage.

I prefer sensing entering air temperature, normally at 2-3ºF differential. In your case you could go to 4-5ºF diff to slow down the cycling.

[LGM]

Short cycling can result in compressor failure if not corrected. It's made worse in the winter. When you short cycle, the compressor doesn't run long enough to return the oil and if you log enough in the evaporator the compressor is kaput.

One option you have is to install a hot gas by-pass. That way the system will run longer and oil return won't be a problem.