prep table help

[self employed 1]

working on a randall 4 door prep table with absolutly no model info.

in the lower section there are 2 evaps with txvs. there is a static loop for the upper portion also with a txv. there are 2 solenoids, 1 pressure switch and 1 comp.

unfortinetly for me this is a built in table and i cant follow the piping/electrial. can anyone tell me sequence of opperation as far as solenoids and circuits. im guessing one for the box and one for the upper deck?

its an older system been working fine. tecumpsi mod # aka9441axa, 414-b. problem im having is low suction pressure about 4-5 lbs 125 high. weird thing is the lower portion is cooling fine upper portion at best 57.

compressor capable of pump down, high side climbs if cond fan disabled which tells me good valves. when running sight glass full and cond endloops hot.

what controls the other solenoid? there is a stat in the box for one of the solenoids, what about the other one? any help would be appreciated, this is a larger account i recently aquired. thanx in advance.

[thegoodhumorman]

maybe theres another hidden away inside evap area-
kairak i think twas actually had 3 sol valves in fzr section behind fan /coil cover.
burned out all the time...

[markettech]

Does the table have a switch to turn the refrigeration to the upper rail on and off?

2 Solenoid valves - is each one on a branch of the main liquid line or is there one on the main line?

[markettech]

Originally posted by markettech
Does the table have a switch to turn the refrigeration to the upper rail on and off?

2 Solenoid valves - is each one on a branch of the main liquid line or is there one on the main line?

Anyway....It is possible the upper rail could be running off pressure control with a switch to shut down the solenoid. Lower part is controlled by temperature - tstat cycling this solenoid. My guess is the lower stat is a coil sensing, constant cut-in to allow for defrost.

I'd be looking for power to the solenoid feeding the upper rail. Find out if a switch is wired in series with either coil. If solenoid is energized and liquid is getting to the expansion valve - could be a bad txv.

I should know this, but what is 414B again?

[icemeister]

Here's (http://difc.difoodservice.com/MarketingMaterials/OperatorsManuals/RandellManuals/8000N_Series.pdf) the manual for Randell's prep tables with the refrigerated top rail. This shows a TEV, thermostat and solenoid valve for both the main evaporator(s) and the top rail and a low pressure control to control the compressor.

The older style units I've worked on didn't have a thermostat for the top rail as its temperature was basically controlled by the LP control setting and the bottom refrigerator section was controlled by its constant cut-in thermostat as markettech said. The new ones must get the t'stat for both.

Your suction pressure seems a bit low, but being it's a blend the TEVs may need to be opened up a tad or the inlet screens cleaned . Try to check your superheats and go from there.

[self employed 1]

414-b is hotshot,im going back today. i will check all these suggestions.

[self employed 1]

ice and everyone else thanks for the info. i downloaded the manual and called randell. got the info i needed, concluded that it was the txv. today replaced the txv. the exsisting had a bad power head which was non detachable, also dryer, refrigerant weighed in the 16 o.z. charge per the manu. started it up and she cooled great. my question, why is there is a sight glass? besides some one added it along the way, and why at 1/2 full? (I AM UNDER THE ASUMPTION THAT YOU NEED A FULL COLUMN OF LIGUID TO THE TXV. opps hit the cap key, sorry). what do you think of that. also my suction line was frosted at the comp. when i checked s.h after the coil it was high 28. i think it is under charged.

[jumperwire]

i dont think you have a built unit with hot shot i dont think anyone is using hotshot as a factory charge seems it was put in as a replacement for r-12 or 134a i hear on low temp refrig S.H should be around 8-12 back seat txv 1/4 turn for every 4 degree S.H drop approx.

[Dowadudda]

Those units aren't too bad either.

[Freezeking2000]

Originally posted by Dowadudda
Those units aren't too bad either.


Yea i Like hem units except to changethe L.L. sol. in the mullion! fan coil unit....that sucks!