Compressor problem the low side pressure is 20 p.s.i. and the high side is 240p.s.i. and the half of the body of the compressor is forming ice,and having a loudly sound. is it normal?

Generally, low side is around 20-25 PSI and High side is about 235-250 when unit is close to operating temp. Expansion device effects this to some degree such as a cap tube can restrict and affect pressures as well as the amount of the charge in the system. Compressor efficiency is another.

Ok, basic refrigeration here. The 'high side' contains the high pressure vapor leaving the compressor and going to the condensor to condense into a high pressure liquid. The 'low side' contains low pressure refrigerant vapor within the evaporator and the suction line back to the compressor. The same amount of vapor has to return to the compressor as left the compressor. So thinking about pressure solves the problem....High pressure equals small line...
Low pressure equals larger line. The low pressure vapor will fill a larger space than high pressure vapor so it has to travel in a larger line. The suction side is the bigger of the two and if the unit is functioning, it will be the one cooler to the touch.

Though this is basically correct in theory, it is not a totally perfect way to descsribe an answer to your question, but it was fun to try.

as long as you recovered the charge, pulled a vacuum, changed the filter/dryer, and added the correct amount of refrigerant as a liquid, you should be good to go.

a short cycle usually means it is cutting out on high or low pressure.If its low pressure add gas.If its high pressure make sure condenser coils are clean.amp check compressor if its real low its low pressure if its real high either high pressure or bad cap or bad compressor windings.

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If there is no cooling at all , before we go further we must confirm the first step of confirming the compressor and gas pressure. So shut off the fridge and leave it off while you clean and check the evaporator for frost. If frost is seen it is a good indication as the compressor is working with sufficient gas within.
Now after about 6 hours plug in the fridge to start. Observe cooling to happen in about one hour and ice to from under three hours.
Earlier make sure that the thermostat was set to normal mode for freezer and fridge. If there is no ice formation we have a big issue as the compressor and gas must be checked out. If compressor is running check the pressure, get help to test gas pressure. If not you will need to fill up ,If gas pressure is good the possibility of the compressor being inefficient is high. In such a case you must take consensus to estimate and decide, if RPM of motor is low check capacitor.
However if Ice forms then observe the fridge for about 24 hours for cooling to continue and the fridge to cut off. If not the auto defrost timer, or the thermostat must be checked.

The ventilation fan that circulates the COLD air from the evaporator coils could get clogged with frost and so could be jammed. Also the wires to the fan can be worn out due to the frost. If so check if the defrost timer works to switch the heater to remove the frost. Also the check if the compressor is shut down by the timer /thermostat . If the heaters are not working, check continuity of the heaters.
So attempt to test using a multi-meter / clamp tester from the outside and make your observations so that we come to the solution.

Please check this link for tips to work.

http://www.espares.co.uk/advice/fridges-and-freezers/a/2

Thank you for using Fixya.

There are a lot of variables that cause high head pressure. Be sure the cool ing fan is operating properly. It should come on whenever the condenser coil feels warm to the touch. It will cycle on and off as the pressures change. A clogged up coil will also cause high head pressure. If you don't have sufficient water flowing over the evaporator plate, where the ice freezes, the head pressure will go up. You need to check the low side head pressure as well. Weighing the charge is a good start to charging the machine , but the first question I would ask is why are you charging it? Was there a leak, or compressor change?
If you had a compressor burnout, did you replace tthe drier-filter?If not, it may be stopped up from burnout residue. That will also cause high head pressure. If you did not vacuum the system there may have been refrigerant still in the system before you started the new charge. Check the items I mentioned and see if that helps.

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.

Good Luck and hope this gets you started.

The 3 beeps indicates that the freeze cycle is longer than 60 minutes. with the suction pressure at 20, it sounds like low on charge (freon). I believe this is an R 404-A unit. Other things to look for are: Stuck float switch (in the up position), Water valve leaking, hot gas valve leaking, txv not feeding properly, weak compressor. Look at high side pressure too. It should not go below 210 psi during the freeze cycle. Low pressure should be in the middle to upper 40's psi.

Let me know if you need more.

The first place to look is to check the charge. Using guages check the low and high side pressures and their relationship to one another. I'm assuming your unit is a R-404 unit which, if fully charged and the condenser is clean, and the fan is operating, should have about 210 to 250 high side pressure. Other things to check: evaporator coil ice/frost free; defrosting properly to obtain a clean coil; all evaporator fans running. If low side pressure is above 30 PSI you have a weak compressor. Whatever, fix the Traulsen unit, its head and shoulders above anything else on the market today.