High Humidity - At Wits End (coming soon to theaters)

Hey reddit. I am a redditor and fairly handy business owner that seeks to harness the power of the collective internet to help me solve my high humidity problem on a refrigerated bakery display case. It is a little over a year old and has always had high humidity in its refrigerated space.

Outside air temp is relatively stable at ~70-75 deg. Outside humidity is ~25-30% relative humidity. The refrigerated space maintains temp just fine at ~40 deg. However, the humidity is super high at 80%, which is damaging to my pastries and much higher than my other refrigerated displays cooling to the same temp. Fondant sweats. Decorative sugar dissolves. My target is the ~65% - ~70% RH that my walk-in and other refrigerated cases are able to maintain. I have had several techs come out from various companies that are reputable in the area and they all have given up without arriving at a conclusion.

One route is to go diplomatic full Karen on one of these companies that have attempted to service the unit and given up.

Another is to narrow down the cause on my own to kick the service tech towards an action instead of shoulder shrug. I am familiar with the science and have some tools to attack this myself, but would rather not have to. I have 3 theories which I believe to be plausible and I seek help to diagnose the problem myself:

1. Unit is short cycling and therefore not cycling long enough to dehumidify
   1. Not sure how to test this. Put a small heat load inside?
   2. What would a permanent fix be?
2. Evap temp is not cold enough to get moisture to precipitate out of the air
   1. How to test? Is this where I would need to figure out the superheat and perhaps make it smaller? (lower the temp). What are the side effects of this? If i ensure the refrigerant (134a) is warmer than the saturation temp prior to entering the compressor suction, does that mean all good?
   2. What's the remedy? Is there a thermal expansion valve that can be opened up to allow more refrigerant to flow?
   3. What about removing evap coil fins? (irreversible damage is definitely not a first option for me)
3. Evap fan speed is too high and warming the coils too quickly. I added a fan speed controller to lower the speed, but there was no noticeable impact.

Some Things at my disposal: Vacuum pump, recovery pump, manifold with analog gauges, cans of 134a, lots of willpower and determination. Cheap mini thermoelectric dehumidifiers.

I realize my questions may be rudimentary for those experienced in the field and apologize. I would love to leave the work to a professional, but that route has been a dead end so far.

submitted by /u/javanat0r
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