beverage cooler evaporator freeze up problem

[TempcoDog]

This customer has a new air cooled condensing unit (4 months old) on this old 2 door glass cooler. critically charged cap tube system. I was called as cooler was warm. found evap frozen solid...I figured it was the cold control as it wouldn't shut the compressor off when i turned the dial...I disabled the compressor to keep evap fan running to defrost...returned and re-enabled compressor and the cold control did turn compressor on (although control wasn't in ice I couldn't turn it off initially)

Placed guage on suction service port as I wanted to check superheat and I placed other on side to confirm both sides balanced out on off cycle..they were.....

my question is once system started suction pressure worked it's way to 5-10 psig (R-134a system) so I'm thinking it may be low on charge but suction temp was 43F...am I on right track or what am I missing??

[Pingosize1]

Several concerns, if the evap. Was a block of ice freon charge was probably fine. If you took readings for suction and discharge on a critically charged system you may have lost gas in the process. This could explain slightly low suction press. Temp. Control should be mounted in coil for sensing ice build up. Do the doors seal or does the box get a lot of use? This can cause icing as well. Recommend weighing in the correct charge and putting the temp. Control bulb in the coil.

[2sac]

I'm more concerned that you put your guages on. I would have watched the box cycle multiple times with my digital thermometer, and checked line temps before I'd throw guages on a criticaly charged system.

am I on right track or what am I missing??

A couple ounces of gas is my guess

[TempcoDog]

thanks...for these systems I use seperate guages without hoses, just quick connects so not to lose gas...yes sensing tube is mounted inside coil...it's worked fine for months...it's an older unit that doesnt seal the greatest and it worked fine during the summer where as the location of the condensing unit is above in an attic space that gets very hot...ya I didn't think it would be low on charge

[2sac]

I'm lost now. A remote condensing unit with a cap tube???

[evilsanta]

I have never encountered a remote system with a cap tube. It has to have a txv.

[TempcoDog]

no sorry...the cooler is build into a wall...evap in an insulated box and condensing unit in unconditioned space above..as opposed to most systems we see with everything below that you can remove to work on...this is an old building, with older equipment except for the new condensing unit...

[ETC1]

5 -10 to Psi indicates low airflow low charge or partially plugged drier or cap tube. Due too hot location of condensing unit and POE oil I would suspect a cap tube problem.

[Pingosize1]

If the attic is hot in the summer it's probably cold now? Low head pressure equals low suction. Where are you located? You may need a fan control.

[VTP99]

My thought was the guy that installed the condensing unit 4 months ago was probably charging it when there was a much higher ambient.

[TempcoDog]

yes it's not outdoor ambient cold, but with the summer heat it gets quite warm in the partial attic space it is located......but as it's winter here on the west coast and not below freezing temp isn't affecting the condenser... I thought of a restriction, but the pressure balances out on both sides relatively quickly like you see on properly operating systems...low charge means leak..which my first step is pulling charge and weighing it...thanks guys!

[bacciagalupe]

how can you weigh in the charge on a remoted cap tube system ? the unit needs a expansion valve and a receiver and cold controls to work properly

[carmon]

i concure.....