Salad bar unit?

[fitzyfitta]

Had a late call today at a local collage for a salad dar not working. I've never worked on this type of equipment. The unit had top section cold plate i believe where they kept salad fruit in bins and the bottom section had 3 doors and it's own evap, fan, dial stat and solenoid.
The unit was made by Carte Hoffmang
m/n cc-10012 mfg date 6/93
Compressor copeland feem-0050-1aa-201
Danfoss txv tf2 r12
The unit looks rebuilt and was converted to mp39. There was sightglass installed was flashing. Also had suction line frosting back to comp. The upper section was controlled by a solenoid that was energized by a on/off switch. I'm going back in the am with some mp39 and recover refer and try to find a leak. My question is what type of press/temps and s/h should i be looking for and should i charge with both circuits operating? Any inpt is always appreciated thans Fitz.

[MwTechInc]

Charging........IF the condensor is located in the unit ,then the nameplate data in oz's should be used.

Condensor remote?, then line size and length comes into play.

Appears to be made like a Delfield where two systems run off one compressor, you should find a TXV on the top section.

Just baseline all the componets, ie: make sure txv bulb is actually on line,thermostat cap in in evaporator etc fans actually working the right direction, clean coils etc.

.Otherwise these things will drive you nuts.

[hvac wiz 79]

MwTechInc nailed it ... so if i may just add with the lower section cycle it by itself & observe the pressures on start up & first minute into cycle providing coil is clear & fans are running .. this can help you rule out trash in the TEV or its power element maybe losing charge before you go adding some refrigerant in it

[james122964]

you never said what t he actual complain is. Frost to the compressor is normal on delfield units because the top rail normally runs down around 20 degrees.
There should be 2 solenoids one for the box, one for the rail.

I have found delfields have the ends of the evaps in the box always rotted and leaky.

The top rail on this type of system usually is controlled by a lpc, and the box by a tstat.
If the box is satistfied it will shut the box soleniod off, then the top statifies when the rail is cold enough to drop the system pressure.

Jim

[fitzyfitta]

I didn't even really check the top section, only energized the solenoid to make sure i have flow to the top. The suction was frosting with only the bottom cooler running. As i said sight glass was bubln'. Is that normal for mp39. how about evap or suction s/h. What should i be looking for at each. They said the like the bottom cooler at around 40. So i suppose i'll correspond my press to temp and look for a proper split across the evap. What do you feel is a good split for the cooler. I did notice when i shut the cooler dal switch to off the unit would pump down and shot off. Also noticed some bluish build up on the suction lines near the evap. Is this from the acididy of the product? Thanks guys!

[james122964]

I didn't even really check the top section, only energized the solenoid to make sure i have flow to the top. The suction was frosting with only the bottom cooler running. As i said sight glass was bubln'. Is that normal for mp39. how about evap or suction s/h. What should i be looking for at each. They said the like the bottom cooler at around 40. So i suppose i'll correspond my press to temp and look for a proper split across the evap. What do you feel is a good split for the cooler. I did notice when i shut the cooler dal switch to off the unit would pump down and shot off. Also noticed some bluish build up on the suction lines near the evap. Is this from the acididy of the product? Thanks guys!

If you were on a hot pull down you could see some bubbles until the TXV throttles back.

I would set the lpc for 20 degrees, sorry don't remember what that is for mp39, and set the tstat to # 5 on the dial, it most likely is the problem, they stick on or off when they get old. If they even turn. I have notice that when they start to go, they will pull down, but the differential to get them to cut in gets higher and higher.

I think you have plenty of refrigerant, I have seen these things limping allong when there was barely any gas showing the in glass.

Jim