Silly Fridge Problem

[Brian_UK]

Here's a little problem for you.

Petrol (gas) station upright chilled display unit with twin evaporators, TXVs and solenoid valves.

Unit was running on R12, changed to R413a in Nov '00, compressor failed last week. Unit was not new when installed in early 2000, year date is 1990.

One of our A/C guys fitted a replacement L'Unite R404a condensing unit, two new TXVs, filter driers etc, last Friday. System charged up and left running with cabinet down to temperature.

Unit failed to hold temperature and would not run from Saturday morning, customer switched off evaporator unit.

I went to site this a.m. having been told that the LP pressure switch may not have set properly. Standing pressures were - suction 2.0 barg, discharge (receiver outlet) 10.0 barg. I lowered the LP pressure setting as the pressure switch was open circuit, sorry - pressure switch is combined LP/HP auto reset. The compressor started and immediately pumped down again; I hadn't powered up the evaporator yet DOH!

Switched on the evap unit, heard the solenoid valves open, a short rush of gas and then nothing. Returned to the condensing unit and found that it had tripped on the HP switch which was set at 25.0 barg; standing pressure on the suction was up to over 5.0 barg which at least showed that something had happened.

Where would you look next ? sorry no prizes for this one.

[subzero*psia]

Can you give us more detail... TXV capacities, evaporator coil capacities?

I hate to admit it but I am not familiar with the bar system anymore... never have to deal with it and the old saying still goes... if you don't use it you lose it. I will check some of the conversion boards maybe figure it out from one of those.

Are any of the system pressures looking okay? Does the unit trip immediately or does the pressure slowly rise up till it trips?

Has anyone checked the reciever tank king valve for open position?


Are the condenser fan motor(s) spinning in the correct direction? Are the evaporator fans working?



Yours in refrigeration....
Dean

[Brian_UK]

Originally posted by subzero*psia
Can you give us more detail... TXV capacities, evaporator coil capacities?

Are the condenser fan motor(s) spinning in the correct direction? Are the evaporator fans working?

1) I didn't give too many figures Dean because it was such a stupid fault.

2) Yes the motors were running...........but.............

The condenser fan blade had fallen off the motor shaft

Now how can you allow for that sort of fault on a brand new piece of kit? Or do we have to check everything that the manufacturer puts a nut on or a screw in?

Anyway it's running again without problem.