Searle cellar cooler control problem

Hello,

I need to visit a bar in the morning (not quite yet alcoholic) to have a look at a searle cellar cooler. Another refrigeration company have been out and have been unable to remedy the fault. This is what I have been told.

Twin fan searle evaporator in the cellar, on the nameplate stating a medium of R12, R22,R502. Upstairs a Unite Hermetique condenser/compressor. Plate on the compressor shows it runs on R404A. First thing that worries me is even though I have been told the cap tube will run on 404A, the oil is not compatible-mineral for the older gases and POE for 404A.

The standing pressure is around 100psi-ambient temp was about 16-18 degrees C. Over the last few days the evaporator had been icing up, so they were switching it all off and then restarting it when the ice had melted. Since I think the end of last week, they are switching on the control box and the compressor and condenser fans momentarily start and stop straight away. On the control box there are two contactors- I am assuming one for the compressor and the other for the electric defrost, and a main RCD with a bank of breakers inside the box. The contactors try to pull in, but trip straight out again along with the main RCD.

I spoke with the customer and he says that the other firm had told him the start capacitor was to blame, which I believe isn't likely. The interesting thing is that the incoming power to the control box from the mains is 240V, but he says that at the condenser the voltage as it goes into the isolator is only about 180V. Apparently the compressor isn't grounded and is OK. When the lives are taken out of the electric box for the compressor, the breakers don't trip, but obviously the contactors don't pull in either as the whole condenser was isolated.

For starters I don't think it possible to run the system with incompatible refrigerant ratings, but can't understand where the voltage drop comes from, so I am assuming the low voltage is causing the compressor to draw too many amps and trip the breaker. I am leaning towards a control problem, but have no clear explantion for the sudden ice. Apparently the condensing set was installed about two years ago-pipework is original.I would have gone over the weekend except for recovering from flu.

I could really use some ideas on this if you have any !!

Best Wishes
James

Hi James.

RCD is not necessary but good ground is.

I would disconnect all the motors and start checking them one by one ie. if it runs and draw the right currant connect the next and so on, compressor first.

As these units should run with suction temp above 0, there must be a leak some where.
As I recall, the beer in the pubs isn't too cold.

If you are going to flush clean the system, replace the receiver if any present, thats where all the oil and dirt accumulate. That will save you running back to change oil.

POE is bad news. Make sure the unit was not operating in vacuum, if it did the oil need to be replaced. disconnect the compressor tip it over and wait till all the oil comes out. That will also give you a chance to see if it is clean or have metal particles in it.
You did not say if it is a semi or hermetic ( don't tip over semi hermetic :D )

My guess is that one of the motors is leaking and trips the RCD or burnt

Chemi

Hi James
Also check condition of evaporator, any dirt / mould growth on it will also cause icing up ;)

Hi

It's hermetic looking at the compressor model number chemi, but I shall have to send someone else out there anyway because just as I thought I was ready to get back to work today I have managed to get a bad chest infection and am on anti biotics. Haven't been ill off work for over 7 years.
Jasper, I think the icing up is a different issue to the other problem. I am thinking that the motor could possibly be grounded even though I was told it wasn't.

Best Wishes
James

sounds like the expansion valve is not working. this could be why it is icing up. it could also explain the start up problem.
if the comp was full of liquid it could trip on start. check oil heater is working.

Check the solenoid valve. If this is not functioning correctly then this can lead to low suction pressures on start up and trips on LP. Also, with a restricted refrigerant flow throught he valve you will get frosting on the evap even with a full charge.

Hi

Went there myself today. Icing up caused by mouldy evaporator. Chemically cleaned it. A fault with one of the neutrals was causing the other problem, the low voltage meant the compressor wasn't dropping from the start winding as it should. All repaired, and rectified.

There isn't a solenoid on the liquid line Frank, because the evap coil is operating over the temperature which would require automatic defrost, so there's no need to have to pump down during a defrost cycle. Thanks for the input though I always am grateful for your valued opinions.

Still, I sent someone else out there while I was ill-he should have been able to sort it. Can't get the staff these days !!! :D

Regards
James