Faulty meat multi-deck cabinet

[pie man]

Hello fellow engineers,

I was hoping someone might be able to help me on a refrigeration fault.

I've got a problem multi-deck which contains two evaps which are piped up to one condensing unit. The right hand side gets down to setpoint of 0 degrees, however the left hand side runs between 5-8 degrees. If I turn the right hand side coil off, the left hand coil will get down to setpoint which again is 0 degrees.

This HT case is on R404A, contains mercury controllers and network modules. It runs at 1.8 bar L/P either one coil is in demand or both, however pressure will drop down to 0.5 bar for a while then go back to 1.8 bar . The H/P runs at 10 bar which seems normal and the sight glass is clear.

This case was only installed last August and has had several engineers investigate this fault already. I would be grateful if anyone could suggest any ideas on what could be causing the fault.

Kind regards,

Pie Man

[lawrence1]

pie man,
sounds like an old austral twin coil case,,,i would look at the superheat on the tx valve.if it's an alco balanced port tx,,,replace both of them with danfoss.if the valves are alco they are your problem.
Lawrie

[chillin out]

LP set too low?

Could be a few things really.

Chillin

[mikeref]

Pie man, so.. either left or right will reach temp when cooling for both is not called for. So i would say that there is either a problem with the size of liquid line, or problem with the distribution. Maybe liquid feeds one tx then with a tee, the second tx gets supply. In other words, if both valves are feeding, the one with the shortest run will starve the second. If liquid line is wrong size, then same conditions will apply. Sight glass will show clear as it is not showing condition at the tx valve.. Mike

[Royal241]

I agree with Mikeref.

[Goober]

Put a sightglass in the liquid line directly prior to the TX, one of those male/female sightglasses can be fixed directly to the TX. Then you'll know fairly quickly if one of the valves is being starved of liquid when both are calling for cooling.

[pie man]

Thanks guys for your comments. Got a call from an engineer today, the cabinet fault has bounced in again. He's been there most of the day and found out there original problem was do with the solenoid valves which were not wired correctly and the installers went back to 'fix' the problem. He's sure even though both coils require cooling only one solenoid will open hence starving the other. He's gonna contact our manager and try to get whoever installed back to site.

Will keep you guys up to date and hopefully get some answers. I'm going back on site tuesday.

Thanks for your replies,

Pie Man

[mikeref]

O.K. Not even my usb plasma light could see that one on the horizon. Thanks for getting back to us.. mike.

[pie man]

Hello guys,

Went back to site today with another engineer, we found the left hand coil was iced up on the expansion valve after the orifice. Checked the orifice, was blocked hence causing the pressure to go into a vacuum. Replaced that but still no affect. Therefore concluded the soldered exp v/v was goosed. Replaced and now getting down to temp fine.

Pie Man