Table Top Salad Bar and Milk Storage Unit

[serviceman3]

The service call was that the Salad bar of this table top system wasn't cooling. I haven't worked on to many of these systems. I was wondering what these were actually called frost tops? The salad bar and milk storage section run off the same compressor in a cabinet underneath. They have 2 txvs on this. These txvs are made by a company called AP Controls Model 209 1/2 ton. What is strange is that there is a additional adjustment on top of the power head assembly. What is this for? Also it appear like the milk storage section of this thing has a Epr valve on it. Why would they be using that on this and what does it need to be set at. This unit has no manufacturers name on it. It is in a old school. This unit is probably a 1970 system. They are using MP39 on this unit. Is that a good refrigerant for this application? What temperatures should this thing run at? Do i check temperature in the actual metal plate?

The overall description of how this looks is the salad bar section is a metal tray recessed down into the table. The milk storage section is recessed all the way down into the cabinet area and has a removable door to access the milk.

Any help on this will be appreciated. Thank You

[FEISTY]

A quick guess would go like this. Top is operated as a cold well. Static coil cooling keeps the walls cold with the bottom 1/4 of the enclosure frostfree. This is due to manufacturer not running any coil along bottom of sides since cold settles and it saves money on copper. Top and bottom sections are individually temp controlled. The coldwell by a pressure control and the bottom milk section by thermostat. The choice of ***** is fine if original was R12. You need to verify what the system was designed for to know if substitute ***** was correct choice. My rule is NEVER SUBSTITUTE ***** if compressor is 10yrs or older. The new gases have a way of not being friendly on older compressors. If you have an even frost pattern in coldwell, chances are you're ok. Before offering any more advice, you need to check the compressor information to verify the ***** and if there is a temp problem in the milk section. Isolate which section has the problem and go from there. Good luck.

[monkey spanners]

The EPR would be to prevent the milk section getting too cold, i expect the salad section would run at a lower temperature or run longer than the milk section needs to hence the EPR.

What problem, if any, is the system having?