Setting of split air-conditioner thermostat to 20 degree celcius

[Cofreth]

I have a split air-conditioner Daikin wall mounted coupled to R71luy15 condensing unit on R-22.
The indoor room temperature need to be maintain at 20 degree celcius, thus the thermostat was being set at 20C.
Before I can achieve a room temperature of 20C, my suction line starts to freeze from the expose suction service valve all the way until the compressor, low pressure about 50psi, high after expansion in CU 100psi at liquid service valve.
Liquid refrigerant is flooding back to compressor, what should I do now, please advice.
If I charge in more refrigerant to break freezing point, it will easily damage the compressor.
If I release refrigerant from the system to prevent a flood back, I afraid the freezing will occur at the indoor unit. Any way I can tune the electronic expansion valve superheat inside the CU from the CU PCB? thank you.

[The MG Pony]

first off you never release refrigerent, you recover it.

Second what is the SH? may be no isse what so ever, but till we know the SH not much can be said, all so if it is a eev there should be a sensore, check to ensure all sensores are making good pipe contact.

for more detail I'll yeild to others with more experiance in these units.

[Brian_UK]

Having frost/ice on the exposed suction line is due to the suction temperature being at -3°C.

R22 suction temperature should be above 0°C or ±60psi. Check your system for leaks.

[andy32]

sometimes the expansion valves sticks open on old daikins the suction drops as it freezes up and the expansion line is pressure is higher than normal , it can look like its short of gas , it might be worth a check

[The Viking]

First,
Make sure that the indoor coil and filters are clean and without obstructions for the air. (To be absolutely sure, thoroughly clean the indoor coil with a good quality coil cleaner)
Then make sure there isn't anything in front of the unit obstructing the air.
Lastly, make sure your indoor unit is on maximum fan speed.

If the problem persists after this then you will have to get someone in to reclaim the gas to verify the charge, give the system a deep vacuum and recharge the system. If you still got a problem after this and experienced technician should look at problems with TEV and so on.

[The Viking]

Also, just had another though...
What is your humidity level in the conditioned room?

Above 35%?
If not, therein lies your problem.

[Cofreth]

Having frost/ice on the exposed suction line is due to the suction temperature being at -3°C.

R22 suction temperature should be above 0°C or ±60psi. Check your system for leaks.

Now at 50psi suction pressure I am already experiencing liquid flooding back to compressor, if I were to charge it to 60psi of course the freezing will gone, but it is dangerous to the compressor.

[Cofreth]

First,
Make sure that the indoor coil and filters are clean and without obstructions for the air. (To be absolutely sure, thoroughly clean the indoor coil with a good quality coil cleaner)
Then make sure there isn't anything in front of the unit obstructing the air.
Lastly, make sure your indoor unit is on maximum fan speed.

Above mentioned are within parameters, as this ac unit is serving to a computer server room, enviroment is very clean and yes on highest fan speed, thermostat set at 20 celcius.

If the problem persists after this then you will have to get someone in to reclaim the gas to verify the charge, give the system a deep vacuum and recharge the system. If you still got a problem after this and experienced technician should look at problems with TEV and so on.
I just replace a new original copeland scroll compressor ZR36tfd522, new refrigerant strainer and vacuum prior charging in gas.

The first time I attended to this unit breakdown 2 months ago was compressor internal high pressure relief valve activated, by-passing refrigerant internally in the compressor. Probably due to previous contractor trying to over charge the system to break freezing point, compressor running noisy and abnormal high suction pressure. After I recover some of the refrigerant from the system, it runs fine for 2 month then one fine day the compressor is running with abnormal running current and noisy inside the compressor, tripping on error code E6, I suspect the compressor bearing cease and replace a new compressor.

[r.bartlett]

stop the guessing and charge by weight. If it's a comms room and a short pipe run then undercharge slightly. We had this several years ago on some units which we removed 1kg from the std charge to stop flood back.

[frank]

I'll wager a bet that if you look up the indoor unit air discharge outlet and shine a torch on the fan impeller when it is stopped, you will see that it is full of crap from over the years, and this is causing low air flow over the indoor coil. In this instance, it doesn't matter that your filters and coil are clean, because the impeller cannot move enough air to pick up the heat it needs to increase the suction pressure.

If I'm right, you can click on my STAR

[aircon50]

Just to chuck another spanner in the works...... Check the suction line back as far as you can.
Had something similar a few times - poor installation practices (Not mine I hasten to add!!) and kinked pipes. Obviously creates a restriction that causes refrigerant to back up against and start refrigerating at the kink.
If this was my first visit to this installation, and suction valve was frosting, combined with low suction, I would want to check the pipework first. As Brian said, I would expect to see around the 60psig mark.
Of course all the other checks need to be performed - filters, evap coil, humidity etc.
Graham