Panache
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Troubleshooting a freezer system
Just a very quick one. I have been using an ice cream maker for some years as a cold trap, i usually never turn it off, but recently discovered some
ice bulging out of the bottom and thought it best i defrost it.
When i turned it back on the following day it started up as normal but the resevoir never got cold. I then opened it up (took of the cover). As
expected it is the simpliest of devices, a small compressor running through a heat exchanger (grill type thing) then through a coil around the
stainless reservoir (in which you make your ice cream or place your cold trap) and back to the compressor. There are no temperature settings just on
and off.
I blew some air over the unit as it was quite dusty and then turned it again. It still doesn't get cold however the compressor does warm up to around
40C (warm to the touch).
Anyone know off the top of their head what the problem might be or what an easy test or two could identify the problem? the gas is r134a and some
photo's below show the system.
thanks in advance!!
  
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aonomus
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Is there any way to check whether the refrigerant is still there? Where was the ice bulging specifically? Could it have expanded and made a crack in
one of the lines? The refrigerant wouldn't leak until the ice had melted away if there was enough ice too.
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azo
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have youi turned on its side after it was turned of this will cause the oil to fill the condenser and you should sit it up the right way for half hour
before turning on.
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Panache
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the ice was around the stainless reservoir, had i known that i would never have turned it off but i was afraid the coils had iced up, it has been
upright the entire time, as per your suggestion anon i poked the bicycle type vale off the compressor and received a spray of gas so there definitely
is some there under pressure which seems to vote against the possibility of a leak.
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undead_alchemist
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A little off topic.
134a systems a higher leak rate then older R12 systems.
In the past 2 years I recharged 3 pop machines that a friend owns.
Now more then a few years old each, other techs said that it would be cheaper to get
new ones then to fix them. All of them had little to no refrigerant let in them.
I refit them to all run Duracool (Propane / IsoButane mix). All of them ran better then new after.
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azo
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If it has not lost its gas and the compressor is running as you said this would tell you that the thermostat is operating correctly , you can be
tricked thinking there is gas in it but proberly only air
or do you see gas coming out.If it is fully charged and was freezing up the evaperator before this would indicate a tx vavle problem.best to get a set
of 134a gauges and check pressures and i can give you an accurate diagnosis. !GAUGE READING TELL ALL.
REGARDS AZO
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smuv
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Are you SURE the compressor is running? Just because it gets hot does not mean it is not running. Most compressors have two circuits, one is a start
up coil which is engaged for the first few seconds the other is the normal run coil (which is energized at all times, even during startup). If the
start switch is faulty (which is a common piece to fail) the start coil will never be energized upon compressor startup and the motor will essentially
be stalled causing it to heat up.
The compressor will make a humm sound and vibrate slightly when it is running. If you are still unsure, take a good ammeter (w/ at least 10A max) and
measure the potential, if it is really high up around +8 amps you are dealing with the aforementioned problem. A stalled compressor will make a sound
but will not humm or vibrate.
"Titanium tetrachloride…You sly temptress." --Walter Bishop
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Sedit
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Out of all the issues I would be MOST concerned with the ice that had formed from it running day in and day out(correct?), for ever how long, plugging
up a hole. If there is no pressure in the system from freon you should no longer hear that gurgling sound a normal system like this will make. If you
do hear that sound perhaps let it run a bit longer and see if it picks up. It must compress the gas before it can expand it creating your cooling
effect. This requires energy which comes in the form of a compressor. The more it works the hotter it gets.
Check the temperature of the heat exchanger and proceed from there. If there is no difference to only very slight on over a long period of time then
you have a problem. Else it may just need time to warm up.
Knowledge is useless to useless people...
"I see a lot of patterns in our behavior as a nation that parallel a lot of other historical processes. The fall of Rome, the fall of Germany — the
fall of the ruling country, the people who think they can do whatever they want without anybody else's consent. I've seen this story
before."~Maynard James Keenan
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azo
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just another thing to remeber if it has start and run windings like smuv talked about it would mean there would be a capacitor wired in for power
factor correction the compressor will just sit there and get hot if the cap is faulty.
sedit i don't no where you get this heat exchanger bit { IT IS A CONDENSER} meaning it changes the refrigerant from a gas to a liquide before entering
the cooling coil or as a car it would be an evaperator.
regards azo
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leu
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There are many threads on refrigeration problems at:
http://www.refrigeration-engineer.com/forums/archive/index.p...
Chemistry is our Covalent Bond
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Panache
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Well the australian moto is to have a go, which unfortunately i did after post no. 4, i really should have waited as all the advice is simple,
sensible, intelligent and well.......... not what i did.
The compressor, well something in the compressor was clicking on and off every several minutes so i traced the sound to this little bit sitting on the
compressor, (photo 1), given that the compressor said 'thermally protected' and knowing thermal switches can be faulty and seeing nothing else in the
circuit that looked like a thermal cutoff i shorted this component and turned it back on, it started up and began running. Ordinarily it took some
20-30minutes to reach -35C so i went and did something else or maybe the phone rang but i was alerted to the fact that there was a problem by the
light and power going off. When i wandered back up to the office i unplugged the thing, flicked the brakers back on and decided something had burnt
out, because there was a burnt smell in the air. I will now go and check all the suggestions made from everyone and report back, hopefully it is
redeemable however it's now less simple.
 
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hissingnoise
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The pictured item looks like the control switch for the start-winding.
Shorting it would have allowed the heavy start-winding to run uninterupted, leading to a probable burnout of the winding.
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smuv
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Yeah, you should have shorted it for like 2 sec, to get it started and then opened the circuit once the compressor started running. At least we know
what the problem was.
This is a good thread to have though. This is a very common means of failure for these types of small compressors. The start switch (or whatever its
officially called) is a fairly expensive item to replace (like 30 bux) but for continuous operation the assembly may be removed and the start coil may
be connected to a switch. When the compressor is first plugged in, flip the switch until the compressor starts running, then flip it off.
[Edited on 5-25-2010 by smuv]
"Titanium tetrachloride…You sly temptress." --Walter Bishop
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azo
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Running start windings on there own for long periods of time
could burn them out. get a multi meter and measure the resistance of the windings and check windings for infinity to earth.
also on most compressors the start windings run all the time , And the run winding run all the time to just after the motor starts up.
regards azo
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Sedit
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Quote: Originally posted by azo  |
sedit i don't no where you get this heat exchanger bit { IT IS A CONDENSER} meaning it changes the refrigerant from a gas to a liquide before entering
the cooling coil or as a car it would be an evaperator.
regards azo |
No.... I ment what I said.... The heat exchanger. The fins on a cooling unit responsible for removing the heat of compression. Take a central air home
unit for an example. The coil that is placed inside of the house is the condensing coil but the large box that is placed outside is the heat
exchanger. The large unit with the fan on it..... Thats used to remove the heat generated when the gas is recompressed to a liquid else your system
would be useless if it warmed up and cooled down all in the same area. Test to see if this coil is getting warmer because if its not somethings
amiss....
Did that clearify that for you azo?
Think about it man.... isn't the condensing coil nothing more then a heat exchanger? sheesh.
[Edited on 27-5-2010 by Sedit]
Knowledge is useless to useless people...
"I see a lot of patterns in our behavior as a nation that parallel a lot of other historical processes. The fall of Rome, the fall of Germany — the
fall of the ruling country, the people who think they can do whatever they want without anybody else's consent. I've seen this story
before."~Maynard James Keenan
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