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mankam
23-03-2016, 11:49 PM
I would like to ask several questions about R404A refrigeration system:

1.What is the smallest allowable discharge pressure for this type of systems?
2.Does expansion valves have minimum working pressure?
3. Is it normal that suction pressure is about 2bar (-30oC saturated temperature) when cooling is needed to maintain +7oC temperature.

Sincerely,
Mantas K.

Magoo
24-03-2016, 01:48 AM
hello,
Question /1 what ever SDT your select to operate must be reasonably constant, the specific weight of 404a requires pressure to push it around.

Question /2 TXV are selected with a specific pressure drop range to supply evaporator with sufficient refrigerant to do cooling load.

Question 3/ NO , YOUR EVAPORATOR is starved of liquid, due to most likely low discharge pressure. The evaporator super heat will be off the scale same with compressor suction super heat. The compressor will die shortly.
So condenser fan control or a head master controller for low ambients, to get a system balance happening.
magoo

Grizzly
24-03-2016, 07:16 AM
A good question Mankam.
And a brilliant and concise set of answers Magoo.

Gas flow, density and Discharge Pressure have a huge effect, yet many overlook them when fault diagnosing.
Grizzly