A little background first, I am owner/operator of a commercial refrigeration service company, got called on this fish freezer for complaint of temperature not cold enough. Customer found one lower fan motor dead and both ambient air curtain motors were dead. I travelled the two hours to site replaced and checked. Ambairfilters and Honeycomb cleaned at same time. Good even airflow through all honeycomb tested with smokestick.
The fixture is a Hussmann G6F-8U multideck freezer holding frozen fish and shrimp. The problem is that the fixture recently started bottoming out at -10C/14F. It normally bottoms out at -17C/1.4F setpoint is -20 to ensure it never cuts out before then.
This fixture is in a store on the same level 100feet or so away from the LALA-032E-TAC-800 low temp compressor that serves it. Here's some info for you:
Solenoid Valve controlled by A419 temp controller
225lbs discharge(95F condensing)
Suction at 20lbs
Superheat at 6deg but have tested 4 through 8.
TXV is an HFE 1-1/2 RZ strainer is clear on this and the suction service valve on the compressor.
Amp draw of 9.5amps @ 14F 10.8amps @ 28F (12.6 Rated Load Amps)
Standing pumpdown test indicates pressure rise most likely due to leaking suction service valve as I pulled the head and valve plate to confirm no broken reeds or broken con rod on one piston, amp draw would be lower anyways on one piston but it's been checked.
Checked defrost heaters to ensure they were not being energized during reefer cycle. No amps, or voltage to them.
I just downloaded the original fixture manual from Hussmanns site so will be going throught that. The fans have always been on in defrost mode even when the temperature was cold enough. I will check but it looks like this is design as one of the heaters is in the return air duct at front of case and the next 6 inches before bottom evap. First time I've seen one that has fans on in defrost if that is right.
Any ideas on what I'm missing? This occurred overnight from good to not good. Not slowly over time. What are your thoughts?
I appreciate any help, no such thing as a stupid question either. Let 'er fly!