Commissioning issue walk in freezer!!

[COBRAKAI]

Problem: Cold room not reaching temp lowest -15. But with product in it -8

Condenser operating on r404a orifice 2
Sight Glass full, Suction has slight frost back 6 inch from compressor
Evap
Air on: -15
Air Off:-19.9
Back Pressure: 1.1bar (-30temp)
Suction Line temp: -8
Condenser
Air on: +18
Air Off: +35
Head Pressure:225-250psi (+38)
Discharge Line temp: +60

What am I missing!!!!!

[sokold]

it might sound stupid, but have you checked whether the defrost heaters are on.....happened to me once :)

was that suction line temp taken at the evap or a remote condenser ?

[thebigcheese]

Close the door lol

[mikeref]

Fans are going the right way and coil is free of ice? New room pannels used so insulation is not a problem? Snow buildup around evaporator fans?

[Magoo]

Have you checked the evaporator superheat, did you install MOP TXV

[mad fridgie]

Suction pressure to low, head pressure to high. Suction SH to high.
I would suggest incorrect TEV SH setting to high or orifice size is to small (lowing the suction), and maybe a slight overcharge (increasing discharge).
One other point, has this room been designed for storage only or product pull down (-8C product)

[COBRAKAI]

Cheers for the posts.. I am sure it has been designed for pull down but I will have to double check we actually lowered the suction pressure as this was the only way we could achieve it to drop bellow -10 the condenser is operating on fan speed also but going with an ambient of +18 head pressure seems ok. Im looking more to wards the orifice size because everything else seems to be doing its job. We had the evap super heat set for 6k and it would not pull down bellow -10 it was left for hours.

[Gary]

We had the evap super heat set for 6k and it would not pull down bellow -10 it was left for hours.

Are you saying there was 6K superheat at the coil outlet and you adjusted it higher? If so, there's your problem.

[al]

Cobrakai

How did you lower the suction pressure? ("we actually lowered the suction pressure as this was the only way we could achieve it to drop bellow -10 the condenser")
What are the room dimensions and duties of the condensing unit/evaporator?
Where did you measure the suction line temperature?

Alec

[Magoo]

The evaporator is being starved of liquid

[COBRAKAI]

Cheers for the posts again lads..
Went back to site and de-gassed system blew the lines out with ofn and checked over expansion valve. Issued triple vac and re commissioned. System took a few hours but eventually T1 reached -20. T2 Evap temp -26. Was thinking there may have been a blockage or an issue with expansion valve. evap superheat was 9k any more was causing floodback any less would not achieve sufficient temp. subcooling was 8k was wondering if this was ok for a pipe length of 5m? Personally I still feel the system may be undersized due to the volume of people entering the freezer it is a very busy restaurant hence the long time for pull down. product is stable at -18 though. I will post all information including system installed and commissioning data to see what what yous think. Maybe yous could help me adjust it for better efficiency.. In the mean time just got a call out.. Sigh!!!!!