Refrigerated Air Dryer Flooding at Compressor

[AMS]

Hi All,

This is going to come across very long winded, but I'm struggling and any help would be appreciated.

I am trying to charge a refrigerated air dryer with a water cooled condenser controlled with a water pressure regulating valve with R407C (liquid charging abviously) after replacing the evaporator, compressor, TX valve and Hot Gas Bypass valve.

The unit is supposed to take approximately 15Kg of refrigerant, though after only putting in 7Kg, I am finding the compressor to be flooding back with liquid refrigerant with frost / ice building up on the compressor.

The water pressure reg valve is set for a discharge pressure of 1650-1700kPa. The following pressures & temps are:
Suction - 230Kpa
Suction temp @ TX bulb - 12 degC
Discharge Temp (@DSV) - 46 degC
Liquid Temp ent. TX - 28 degC

I've tried fully opening the HGBP valve to bring the suction pressure up and prevent the flooding though this isn't doing anything.

I've added refrigerant up to 11Kg though the suction pressure still did not begin to rise.

The suction line temp is quite high, though from the accumulator to the compressor is when it is indicating the flooding back (accumulator appears to be not blocked).

Does anyone know as to whether I should just keep adding refrigerant as I am worried about the potential damage it may be causing to the compressor?

Or I am wondering as to whether the TX & HGBP valves are fighting one another...

Any assistance in this would be greatly appreciated.

[nike123]

Discharge Temp (@DSV) - 46 degC
Liquid Temp ent. TX - 28 degC

Do you mean discharge line temperature is 46°C or saturated condensation temperature is 46°C converted from presure measured at discharge line valve? What was pressure than?
What is temperature of LL at condenser outlet? Is there liquid reciver?
Do you have refrigerant diagram?

What makes you think you have flooding?
230 kPa gauge pressure is -8,8°C evaporation saturation temperature. Does 230Kpa mean 230kPa absolute pressure?
If temperature of line at TXV bulb is 12°C than you have 21°K superheat and no flooding from evaporator.
You cannot have negative superheat.

Try to be more clear with units and prefixes.

[lana]

Hi there,

Check the TEV bulb location it must be on 5 O'clock. What you are saying is you have little bit of liquid coming into the accumulator which eventually goes into the compressor.
Also is there an oil separator? Is there a solenoid valve before HGBV (this SV must be closed when compressor is off)?

[AMS]

Do you mean discharge line temperature is 46°C or saturated condensation temperature is 46°C converted from presure measured at discharge line valve? What was pressure than?
What is temperature of LL at condenser outlet? Is there liquid reciver?
Do you have refrigerant diagram?

What makes you think you have flooding?
230 kPa gauge pressure is -8,8°C evaporation saturation temperature. Does 230Kpa mean 230kPa absolute pressure?
If temperature of line at TXV bulb is 12°C than you have 21°K superheat and no flooding from evaporator.
You cannot have negative superheat.

Try to be more clear with units and prefixes.

Discharge gauge presure is 1650kPa, Suction gauge is 230kPa. Liquid line temp leaving condenser (water-cooled with no l/rec) is approx 28 degC.
Actual discharge temp @ DSV was 46 degC.

I realise that I can't have a neg superheat, though I have just found an inline strainer on the suction line before the accumulator which had some sh*t in it which I have now cleared and hoping was the cause of the problem. Maybe it was acting similar to a 2nd metering device.

Could the frost on the compressor just be due to low suction (???) which I didn't think could happen.

No unfortunately I don't have a refrigeration diagram of the system.

[nike123]

Discharge gauge presure is 1650kPa, Suction gauge is 230kPa. Liquid line temp leaving condenser (water-cooled with no l/rec) is approx 28 degC.
Actual discharge temp @ DSV was 46 degC.

This gives you subcooling of 12K which mean liquid is logged in condenser. Since you did not overcharged it (by weight charged in), that mean you have restriction, as you discovered later.
But, low discharge temperature of 46°C indicate that there is low, or no superheat at all, at suctin side of compressor, and you maybe have liquid in crankcase.

I realise that I can't have a neg superheat, though I have just found an inline strainer on the suction line before the accumulator which had some sh*t in it which I have now cleared and hoping was the cause of the problem. Maybe it was acting similar to a 2nd metering device.

If you still got same readings after that, than you have restriction on LL also.

Could the frost on the compressor just be due to low suction (???) which I didn't think could happen.

If you have low suction pressure and little superheat at compressor inlet, you than could have frosted suction line and portion of compressor at suction side of compressor.
If compressor crankcase is evenly frosted at some level, you than have liquid refrigerant in crankcase.

http://www.achrnews.com/CDA/Archives...00f932a8c0____

No unfortunately I don't have a refrigeration diagram of the system.

Than what is unit make and model#?

For proper evaluation what is happening we need at least these readings:

Evap air/water in temp
Evap air/water out temp
Low side pressure or saturation temp
Suction line temp at evap outlet
Suction line temp at compressor inlet

Cond air/water in temp
Cond air/water out temp
High side pressure or saturation temp
Liquid line temp at receiver or condenser outlet
Liquid line temp at TXV inlet
The more information provided the more accurate the diagnosis.