Fast & Frequent Cycling

[BryanH]

I've been messing around with the ChoiceVend machine I was given last week.  Plugged it in and the system cools quickly but the compressor ran hot and very long.  I put the thermostat coil in a glass of ice water and it kept running.  So I swapped the original t-stat with the new one from my working Cav USS-96. Now the system runs for about 45-60 secs, shutdowns for about 60-75 seconds and then repeats. The compressor is very hot to touch.  The system is sealed - no taps.  

Do I have a cooling system problem?  Is it worth loading it with cans/ bottles to see if it runs better?

[globalcompressors]

Do you remember the "golden rule" of thumb?

Do you have a thermometer?


Eric

[BryanH]

'> ahhh - treat others as you want to be treated yourself?  '>

.... and, I do have a thermometer.

[globalcompressors]

Right on....

Check where the temperature is at. Does it change much from start up? Are you sure the compressor and fan motor are cycling
off the thermostat and not the overload?  Any frosting or freezing
coils? Does the thermostat cycle the 96 correctly?


Eric

[BryanH]

First the simple answers:
  - Coils do frost
  - On start-up it drops the temp from 70 - 80 degrees down to 30 or 40 degrees before the cycling starts
  - The loaner thermostat works fine in the USS96 machine.

I originally thought that the machine might be cycling on/off from the overload but it didn't do the rapid cycle (minute on - minute off) with the old thermostat, so I decided to see how it ran with product.  

I let the ChoiceVend sit turned off over night. I filled it with 5 rows of cans and bottles. Used the known good thermostat set almost at off.  Hung the thermometer midway up on the rack so it could be viewed through the bottle door.  Plugged it in and timed the cycles.  With product the cycles were now long compared to how my other machines have run.  Cooling would cut-in at 40 - 41 degrees and run for 24 - 25 mins.  It would cut-off at 30 degrees and stay off for 35 - 36 mins.  The compressor is very hot to the touch.

I then did the same test on the USS96 (roughly same amount of product, same t-stat and setting, same thermometer).  It would cut-in at 40 degrees and run for just over 8 mins.  Cut-out at 37 degrees and stayed off for 9 - 10 mins.

Do I need to worry about the length of its cycles or should I be happy that it's working and move on?

Does it make sense that having the machine empty or full would affect the cycling as much as it did?

PS - what was the golden rule?

[globalcompressors]

Full of product = longer in between cycles, holds temperature
better than just cooling the "air" inside. If the compressor is hot,
have you looked at the lower fan, making sure it's moving air? I know it sounds lok a "no brainer" question but the motors can, and
do, slow down when going out. Slower rpm...less air flow.

Okay, next look head on, into the lower coils. Make sure there are
no "dust bunnies" blocking any part of the coil...at all! Any air  restriction will reduce efficiency and raise the temperature of the compressor itself.

Now, 1 final situation...you may have a problem with the compressor. If there is a problem with the head gasket or cracked high side line, bypassing hot gas inside the compressor can, it WILL become very hot to the touch and will mimic symptoms, like I stated above.

Try the simple things first. I don't think there is a leak in the system or the 30 degree temperature would never have been reached.

Now, the "Golden Rule"....of thumb.

Guys, please......when trying to figure out any refrigeration problem.....and you're asking questions......always use a
thermometer. It really helps  us "old tech" guys, when trying to give advice.....at least in my case. I'm old school, I haven't developed my "psychic" skills like some of these young techs. My "Sylvia Brown psychic hand book" hasen't shown up in the mail.....yet. Are they teaching it that way now '>


Hope this helps '>

[BryanH]

Thanks Eric. No dust bunnies and fan is spinning fast but... I'm wondering now if the fan is undersized.  It has 6 small blades and the pitch of the blades is much less than others I've seen. It moves the air but certainly not as much as my Ideal55 (as an example). I'm going to hope that's the problem and try a new fan.

[SquareTopCollector]

when you say there is frost on the coils, which coils are you talking about?  Is frost bad?   I am asking because I have frost on the evaporator coils on my uss-8-64

[BryanH]

FYI only.  Finally got around to trying a new condenser fan.  Machine is still real hot to touch but it appears to be working as it should.  Mid setting on t-stat has it cutting in at around 41 degrees running for 28 - 30 mins then cutting off at 36 where it remains off for 26 - 30 mins.  Thanks for the help.