Fan cycling pressure switch

[tudorice]

Hi I havent had much experience working with supermarket refrigeration, but i've got two upright cabinet fridges that ive had to install. Ive upsized the condensing unit to a 8kw compressor and the cabinets need 4kw each (in an airconditioned environment). Ive never had the joys of working with fan cycling pressure switches, so what i want to know is what the cut in and cut out should be for this unit. Its an r22 system, general ambient temperatures range from 26 - 38 deg c in summer and 10 to 20 deg in winter. The fridge needs to maintain a temp of 3 - 6 deg.

[monkey spanners]

If its a single fan unit i recommend fitting a fan speed control.

If its a twin fan then i would still be fitting a fan speed control, but if you want to use a pressure switch then the fan at the end of the condenser where the refrigerant exits needs to be on with the compressor.
The other fan i would set for a starting pressure of about 230/240 psi and off at 150 psi. You will need to watch how it runs and adjust the cut in pressure to suit. If the differential is too close the fan will cycle too much and burn out....

Jon