Our turbo air freezer has some problem, it is still working, but the temp. is alway above 0 degree, about 10 degress most of then time. It was about -10 degree before. I wounder what is the problem with it? We got some guys to fix it, but it didn't work very well, some fo them say it is because of the compresser is too old, we need to change it, some of them say it is not...do you have any idea what is going on?
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Re: temp. can not reach 0 degree.
Things that need checking:
refrigerant level. Super heat. Condenser clean? Compressor effeciency.
These are things that an experienced tech can check. If you have some experience and gages/ tools, I can give you some things to do but most of this requires experience.
Let me know if I can be of any further help.
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There are different models made for holding different products. Yours has a 1/3 hp compressor for above 20 degs. It may have 0 on the thermostat and may well pull down that far, but -20 would be out of it's reach. Where as it's sister model is made to freeze to below zero has a 3/4 hp compressor. Larger compressor for the lower temps.
why yes there is. Generally speaking, the head pressure should be around the "ambient +30" rule.
That is, measure the entering air temp to the condenser, say 75 degrees. Now add 30 to that and get 105 degrees. Look at a P/T chart and see what the pressure is for that temp which is about 253 for R-404-A.
The evap on a freezer leads the load so, as a general rule, the evap temp is going to be around minus 10 degrees to get a 0 degree box. Coolers are different. So, the pressure for a minus 10 evap is around 25 or so. But the unit has to be close to operating temp. If the box is warm, naturally the pressure is higher. And what influences the pressure is whether or not it's a TXV or a cap tube system.
If a TXV and no receiver, charge by subcooling. If a receiver, fill by sight glass. If Cap tube, charge by superheat.
Hope that answers your question.
This is normal. All commercfial freezers must defrost 3 to 5 times a day, or they will freeze over at the coil and then stop freezing. A timer in your freezer turns off the compressor and turns a heating element on for 10 to 15 minutes. During that time the coil heats and melts frost from the coil. Usually within 30 minutes the temperature will briefly rise to 20 t0 25 degrees F and then quickly drop down to 0 degrees F. The food rarely defrosts in this short period of time..
Every Refrigerator has its own "personality" There is no common
setting for any one refrigerator. I would start with 3
The real solution is what I have always told my customers
Get a refrigerator thermometer and a freezer thermometer
Refrigerator temp should be about 33-37 degrees.
Freezer should be about 0-10 degrees. below 0 is overkill
this is something you can do now. Check this 1st:
make sure that the air vents are not blocked and that you didnt overload the freezer with food
there can be other things that will not bring the temp. below 10 (that temp. is not too bad as long as it doesnt spoil the food)
here are the possiblities:
t'stat is set too low
t'stat is not responding to zero degrees (all that means is it is shuting off the compressor too soon to reach zero)
r-134a freon is a tad low (only takes like 9 oz. if lose 1 or 2 that is enough to affect performance)
the freon is the last thing to check cuase you have to call someone to do that for you...
Well hope this was helpful... check the temp often watch to see if it gets above 20 degrees cause that will spoil you food..
It depends on the control that your freezer utilizes.
If your temp control dial has the numbers 0-9 or 1-9, then you have whats commonly known as a coil temp sensor.
Unlike an air temp contol that measure the air temp inside the freezer and comes on and off with a 3-5° swing, the coil temp sensor runs a little bit different.
With a coil temp control or sensor, the temp control has a capillary tube and bulb that is inserted into the coil either at on of the ends down a guidetube or just into the center of the radiator type fins. This temp control measures the temperature of the coil, and not the temperature of the air inside the freezer. When the unit runs, the coils typically gets 20° colder than the air temp. And when the control satisfies (shuts off), it will not call for cooling again until the sensing bulb has reached the cut-in point which is typically well above design box temp.
So, to quickly answer your question, yes it is possible to have a 25° temp swing and not have anything really wrong with the unit. That is how its been designed to operate and that is how it will operate. Your only option (although not recommended) is to replace the coil temp sensor with and air temp control. That will give you more consistent temps.
Also, when taking temp of a freezer with a coil temp sensor, be sure to temp the product in the freezer and not the air temperature.
Freezers have a sensor that is referred to as a "Fan Delay/Defrost Terminator". It senses the temp during the defrost cycle. Usually, when the evap temp reaches about 50 degrees, there should not be any frost or ice on it. This device terminates the defrost cycle. It also keeps the fans off so warm air is not circulated. When the evap gets to about 20 degress or so, the sensor switches on the evap fans. If the fans are not coming on, either the sensor is bad or the evap is not reaching the proper temp to cause the sensor to turn on the fans.
Hope is helps to clear up some things and point you in a direction as to what might be going on.
I'll try to give you the "Readers Digest" version.
First, make sure there is no ice build up on the evap. Light frost is O.K. as long as it does not effect air flow. (Very Important). All fans need to be running. Again, an air flow thing. There should be some product in the box but not too close to the evap. Again, an air flow thing.
The expansion device can effect your pressures to some degree i.e. Cap tube vs. TXV.
As a general rule of thumb, which I use almost everyday when it comes to pressures:
Low side is based on the temp difference between evap temp and condition space in the box. In freezers, it is almost always 10 degrees. If the box is 0 degrees then the evap needs to be at a minus 10 degrees. That is a pressure for R-404A of 24.5 psi. This only holds true when the temp in the box is approching set temp. I would say, about +10 degrees. 0 Degrees for the evap for R-404A is 33.5 psi.
High side should be ambient temp +30 degrees and then convert to a pressure for the refrigerant.
Example: 75 degrees in the room, +30 degrees equals 105 degrees. Now 105 degrees converted to a R-404A pressure is 253 psi. This will get you very close to the desired high side pressure.
I would look at low side first to see if it is within reason. Don't let the high side get too high. Increases the compression ratio and overworks the compressor.
Your icing problem could be a defrost issue and not a refrigerant charge issue.
The freezer should stay within 5 degrees of 0 while in operation. While in defrost the freezer may reach as high as 20 to 25 degrees. If any higher temperatures are reached your food will spoil as they are defrosted and refroze everyday. If you find that the temperature is allowing your food to defrost you may want to replace your defrost thermostat. This device is located on top of the evaperator coil inside the back of the freezer. It is made to turn the heater off when a temperature of 55 degrees is reached. One other possible problem could be your defrost timer is taking to long to restart the cooling cycle after defrosting. I hope this will help you and please send any other questions you may have, I am happy to help. and dont forget to rate me.