PDA

View Full Version : Island freezer problem



Shamel
05-10-2008, 03:44 PM
Hey guys, i have a 24ft Colcab island freezer in a supermarket. One manuerop compressor feeds 4 x evaps with auto T.X.V's. the problem is that this freezer does not go below -12 degrees on cool days & - 10 on hot days. The coils seem to be freezing all the way. i,ve changed the evap fans to bigger ones but not much of a difference. Could it be that the supermarket itself is not airconditioned or could it be the 35+ meters piping. It worked for +- 10 yrs (-25)without any major problems (according to supermarkert owner).

Brian_UK
05-10-2008, 11:05 PM
Are the TXVs working correctly or are there any blockages in the system?

Also, is the refrigerant charge correct?

750 Valve
06-10-2008, 12:24 PM
could be a multitude of things - need more info to diagnose like sst, sct, superheat, subcooling, case design sst, shopfloor rh and temp, etc.

Gary
06-10-2008, 05:17 PM
For a proper evaluation, we need the following information:

Low side:

Evap air in temp
Evap air out temp
Saturated suction temp (SST) converted from pressure
Suction line temp at evap outlet

High side:

Cond air in temp
Cond air out temp
Saturated condensing temp (SCT) converted from pressure
Liquid line temp at receiver outlet

stevehicks
06-10-2008, 06:27 PM
Had a problem similar to that and found little balls from the drier cartridges, partially blocking the ex valves. That is if the system has a commercial drier on it<?xml:namespace prefix = o ns = "urn:schemas-microsoft-com:office:office" /><o:p></o:p>
<o:p> </o:p>

Shamel
06-10-2008, 07:42 PM
Thanks guys, for all the input but i solved my problem today. Found the evap fans i was using were krap(some cheap thing that we were supplied with. They were the rated wattage but their rpm was much lower than the original fans. Installed some ZIEHL-EBM motors & the temp dropped to -19 quite fast without a load & after 3hrs when i checked it (-17) with a load .The freezer even had that fine mist hovering above it. Thrilled!!!!

Gary
06-10-2008, 08:06 PM
Thanks guys, for all the input but i solved my problem today. Found the evap fans i was using were krap(some cheap thing that we were supplied with. They were the rated wattage but their rpm was much lower than the original fans. Installed some ZIEHL-EBM motors & the temp dropped to -19 quite fast without a load & after 3hrs when i checked it (-17) with a load .The freezer even had that fine mist hovering above it. Thrilled!!!!

These two temperatures would have told you the problem immediately:

Evap air in temp
Evap air out temp

Slower moving evaporator air loses more heat to the coil, therefore the air out temp (measured close to the coil) is lowered and the delta-T (difference between air in and air out) is excessive. High delta-T is a dead giveaway for airflow problems.