I need some advice on a walk-in cooler.
The evap coil has a new TxV, no defrost element, and the fan is wired directly to a light switch (always on). The rooftop condensing unit (tecumseh w/ reciever, R-12, 115V, 13.2 RLA) is controled by an in-line temp. sensor (on/off - johnson controls) hanging in the cabinet, and a grasslin defrost timer (on roof).
The high side was 110psi w/ a subcool of about 8*. Superheat is around 35*. There's almost a 20* rise in refrigerant temp from coil input (~20*) to coil output (~40*). The air temp difference over the evap coil is only 3-4 degrees, which is a problem. I've checked for temp. drop/rises on both lines and there don't seem to be any restrictions. I have been told that the entire coil freezes up, but I've never actually seen it that way. What's worse, the walk-in has reportedly never 'really' been cool enough.
Here's the deal - this equipment (along with alot of other antiques) is in my family's place of business, and after constant complaints about the HVACR contractor they use, I decided to take a look around (commercial refrigeration isn't my thing). Long story short, he's not allowed back on the premises and I have no faith in anything he's done, including the new TxV. I also can't trust whoever worked on it when it 'belonged' to the last tenant, as someone 'resized' the cooler with a HOLLOW wall (I fixed that few months ago after someone removed a picture from the wall and found a cold, wet, moldy, nasty surprise).
So here's the $10,000 question: from what I've described, is it possible that the TxV is the wrong size or way out of adjustment? Could it be that the entire system is completely undersized? I couldn't find any plate data on the evap coil, but here's some pics of the setup:
Any help/insight would be greatly appreciated.