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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.
Compressor should rapidly bring pressure down from standing pressure to running pressure when switched on. If no change, compressor not pumping. Make sure the line tap valve isn't leaking, and the gas you used was correctly charged.
Okay first True uses capillary tube not an expansion valve. You say the compressor vibrates not cooling ? If the valves of the compressor are bad, he may mean internal valves but usually pressures would not be good. Give a little more detail please.
Take the top cover off that is next to the compressor,. That cover is about 30 by 30 inches. You will see two fans and an evaporator coil. Several things can happen. First these fans won't come on until the coil is somewhere around 10 degrees or if the door is open. So, once the freezer has been running look under the big cover and be sure both fans are running. If one or both are not running it won't pull down to 0. Also look at the coils and see how much frost has accumulated. If your defrost timer is not working it may be frozen over. When that happens air is blocked from reaching the inside of the freezer. While you are at it, fell of the coils if they are only partially freezing, you may be low on freon. If you have gauges to check the freon charge, check both the high side and the low side pressures. If the high side is less than 200 psi, you have some freon, but maybe not enough. If the high side pressure is 300 psi, you have something blocking the freon from returning to the compressor. Usually a blocked cap tube or a malfuncting expansion valve. Finally check the condenser coils which is the radiator thing out where the compressor is located. If it clogged with dust and grease, it will not dissapate the heat from the freon and will intefere with the operation of the entire unit. Clogged condener coils are probably the number one cause of burned out compressors. Good luck.
The McCall web site has nothing easily found on the 7-7045FT unit.
In answer to you questions, first, what is the expansion device. TXV, Cap Tube, or something else?
Low site pressure will be dictated by the super heat. The high side, in many cases, is usually ambient plus 30, then convert to psi.
Let me know if you need more info. And please double check the model number/ serial numbers.
The waterinlet valve on the back of the unit where the
water supply comes in can have a slow leak and will cause ice to buildup and
block the fill tube. Disconnect the ice maker line from the valve and watch to
see if it has a slow drip. It doesn’t take much to eventually block the fill
The valve can leak because of sediment in the water
preventing it from closing or low water pressure.
You can thaw out the fill tube and replace the inlet valves.
Possibly a bad valve but more likely not enough water coming to the unit,follow the water line from the back of the unit to where it hooks to the pipes there is usually a little saddle valve there,try closing it all the way and then open it back up check the water through the door and see if the pressure doesn't improve.
You can also remove the Ice maker clear out the fill tube and sit a cup under the end of it for a day or two if you get water in the cup and Ice in the tube you probably have a solenoid valve that isn't closing completely.
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.
Most all cooling systems need to be in an ambient temp of about 60-65 degrees. If not, it needs a low ambient control. This helps keep the high side pressure high enough so you have the proper pressure drop accross the expansion device. This applies to coolers, freezers, a/c units, and so on. I also think, if it keeps things frozen like you want, where's the problem? You make have a control just acting stupid.
That system has a restriction. Most common at TXV valve or capillary tube. Will need to be replaced by Refrigeration company. In this video I replaced TXV valve and filter drier due to the same issue You have. Its Ice Machine, Low side was at 5 PSI, High at 250PSI : 404A; should be around 55-65 Low; 250 -275 High. Replaced drier and TXV, machine works proper.