We are charging Gas 404A for -45C deep freeze

The ideal suction and discharge pressures for a Flex Ice Machine using 404a refrigerant can vary depending on several factors, including the ambient temperature and the load on the machine. However, here are some general guidelines: Suction pressure: The suction pressure should typically be in the range of 30-45 psi (pounds per square inch) for a 404a refrigerant system. This pressure corresponds to a saturation temperature of around 20-30°F (-6.7 to -1.1°C). Discharge pressure: The discharge pressure should typically be in the range of 225-250 psi. This pressure corresponds to a saturation temperature of around 100-110°F (37.8 to 43.3°C). It's important to note that these are general guidelines, and the ideal pressures can vary based on the specific conditions of the system. It's also important to ensure that the pressures are within the manufacturer's recommended range, as pressures that are too high or too low can indicate a problem with the system. If you are experiencing issues with your Flex Ice Machine, it's recommended to consult a qualified technician for assistance.

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.

evap temps usuall run 10-15 degrees below the box temp.This a generally accepted rule of thumb.

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.

Did you replace or add a filter drier at compressor replacement? It may have a partial blockage at the inlet to the evaporator.

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.

Depends on how technical you want to get. Generally, measure the ambient temp of air entering the condenser coil. Add 30 degrees to that temp and convert to psi using a P/T chart. This will get you to a starting point.Remember, charging a "Hot" box takes time. Don't over charge.

For a 404 system pressures should be about 60/350 Remember when you recharged always with the freon drum upsidedown so liquid gas is going in to the system.But if it's freezing up could be the thermostat or the timer or the heaters.

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.

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