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Re: low suction pressure high head pressure
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.
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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.
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.
God day, Some thoughts. 1. Are the evap fan motors running, and at full speed. That would give you abnormally low suction pressure. 2. Cap tube sized too small. or partial restriction in the dryer cap tube/dryer when brazing in the lines. 3. Low ambient. What's the temp the machine is running in. 4. Over sized compressor. 5. Moisture. God, 134A is touchy on that one. 6. Was original cap tube soldered to the suction line to create a heat exchanger. Needed on many apps. Definately would cause flash back on start up. 7. Superheat a little low, should be 12 to 15 degrees.
You need to split the delivery and return tubing, then install a solenoid in each delivery tube. The solenoid valve will be controlled or powered by a thermostat in each compartment. You then install a low pressure switch on the suction or return side near the compressor. This will switch the compressor off when both solenoid valves are closed. Hope this makes sense.
Hey there. First question I have is if you have a heat pump or straight ac. Straight ac is easy to diagnose. Your suction pressure will be high, your head pressure will be lower, not sure how clean your condenser coils are so its hard to say how high. Your amp draw on your compressor will be lower than normal. Also, when looking at the suction pressures, you have to keep in mind what temp the air hitting the evap coil is. If it is warm, that will make your suction pressure go up. Another way to check the vavles is to hold the suction line at the compressor when you shut it off. If the temp goes up the second you shut it off, this tells you the hot gas is leaking through your suction valves. You can also try to pump the system down, then shut it off and see how fast the pressure builds back up, this will give you and idea how fast it is leaking through. Let me know if you need any thing else, I'll be here. seth
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.
if the compressor runs but your not getting cold, 90 percent of the time one of two things has happened. either the compressor valves have gotten weak over time and the process of moving and warming up allowed it to defrost and now it has to pull down from a hot box to freezing and just can't because the valves prevent 100 percent efficiency and it struggles to achieve temperature.however i think most likely is that the delicate , brittle , and highly suceptible steel tubing in the outer skin of the box has ruptured and the box has lost its refrigerant charge. these are sealed systems usually with no place to apply a gage to verify if charge is low or valves are bad. if by some chance it has access ports where you can apply a suction gage, a pressure of 20 to 40 punds is close for a hot box and pressures of 60 and above may indicate weak valves. if you are running less than 10 pounds or in a vacuum then the charge is gone, leaked out . unfortunately a new compressor is usually to big an investment in an old box. new is cheaper! and if the tubing in the case has ruptured, then its inaccessible and box is condemned also. sorry to be the bearer of bad tidings but many times a new box is a blessing and saves you from sinking a ton of money in an old one. imagine your frustration if the compressor went bad cause it was low on freon and you paid for a new compressor only to have it die in a few months also. i am pretty sure you have lost your freon charge and unless you can physically see the leak with soap bubbles right at the compressor piping you are in need of a new box. good luck .
Normal operating pressures will change as the freezer reaches the selected temperatures on the inside. Normals of minus 14 degrees on the inside would be around minus 4 psi on the suction and 150 pis on discharge. Now checking the pressure will require a set of guages that have been purged with the same freon before connecting with the suction line on freezer. If not purged the suction line will draw outside air into the system and cause freezing of air and moisture inside the capillary tube rendering the freezer inoperative, Hope this helps, Sea Breeze