freezer only getting down too 7 degrees

[Fresh P]

hi all

i am new to this site and have a limited knowledge of refrigeration works, i have worked as an a/c install engineer passed my apprenticeship but havent done any fridge work for 4years as i am now a gas & heating engineer.

the company im at now has asked me to look at a problem with a walk in freezer and was just hoping for a heads up if possible from the details

the only information iv bin given is the freezer will only get down to 7 degrees

i know this isnt very much information but was wondering if anyone could give me advice on possible cause's, fault finding, what to check ect

thanks :)

[Fresh P]

i have just found out that it is not a walk in freezer it is a fosters fridge

thanks any info would be great

[monkey spanners]

Dirty condenser, faulty cond fan motor, shortage of refrigerant/blocked drier/cap tube, faulty evap probe terminating defrost too early, faulty air temp probe, faulty evap fan, faulty door switch, faulty controller or set wrong, cabinet in too high an ambient, door seals or door not shutting properly, customer over stocking cabinet restricting air flow, compressor not pumping, previous poor repair work by eejits, etc.

Jon :)

[Tayters]

Check airflow is correct through evaporator and condensor (not blocked with ice or dust and fans are spinning the right way).
Check refrigerant pressures. You might need to fit a line tap as they don't all have access ports. Then it's superheat and subcooling malarky to determine if you are short of gas, restriction or overcharged.

Common faults? Well in my experience I'd have to say controller stops sending an output to the evaporator fan motor because the relay packs up inside the controller or the evaporator has sprouted a leak.
If it's the first case the light will be on for evap fans but no voltage output. I normally link the fan output to the permanent feed next to it so fans run all the time if it's a chiller with off cycle defrost - saves the customer buying a controller. Evap will also be iced. Fans may work off a door switch.
Condenser could probably do with a blow out with nitrogen any way.


If you're not sure then don't be afraid to tell the gaffer that it will need a more experienced set of eyes on it. Heating Vs Refrigeration as you know are 2 completely different trades, and A/C install doesn't bear an exact match with refrigeration fault finding. Easy to come a cropper if you're not sure what you are doing.

Good luck,

Andy.