Freezing problem

[MajinDave]

Hi guys ,

I have a problem thats been thats been puzzling me , i have a room that needs to be cooled to +6*C , and 6 evaporators in that room on the ceeling , 5 of them are 3.2 kw and one is 2.4 kw , and i'm using a compressor thats 12.4 kw -10*C and the problem is that none of the evaporators are freezing , only the pipes near the Thermo Expansion Valve are freezing . The lenght of the pipes from the compressor to the evaporators are 50meters , does this has something to do with the TEV ? because i just cant figure out why the evaporators arent freezing ?

[Andy]

Hi guys ,

I have a problem thats been thats been puzzling me , i have a room that needs to be cooled to +6*C , and 6 evaporators in that room on the ceeling , 5 of them are 3.2 kw and one is 2.4 kw , and i'm using a compressor thats 12.4 kw -10*C and the problem is that none of the evaporators are freezing , only the pipes near the Thermo Expansion Valve are freezing . The lenght of the pipes from the compressor to the evaporators are 50meters , does this has something to do with the TEV ? because i just cant figure out why the evaporators arent freezing ?

What is the evaporation pressure at the coolers, it may be above freezing, if you measure this and the temperature at the cooler outlets it should tell you all you need to know


Kind Regards Andy

[Andy]

What is the evaporation pressure at the coolers, it may be above freezing, if you measure this and the temperature at the cooler outlets it should tell you all you need to know


Kind Regards Andy

Or to put it another way with the load you have on the compressor and the long suction line the evaporation probably is above freezing.

Kind Regards Andy

[MajinDave]

Well i tested and there is good pressure at the end of the line , in the next room there are same evaporators only smaller 1.5 kw , and it freezes and gives great result , but with these evaporators i just cant figure it out why they wont freeze , the others do , and they are in about the same distance from the compressor + - 50 meeters

and i tryed shutting half of the evaporators in the room , eaven tryed running 1 at a time and still nothing .

[Andy]

Well i tested and there is good pressure at the end of the line , in the next room there are same evaporators only smaller 1.5 kw , and it freezes and gives great result , but with these evaporators i just cant figure it out why they wont freeze , the others do , and they are in about the same distance from the compressor + - 50 meeters

and i tryed shutting half of the evaporators in the room , eaven tryed running 1 at a time and still nothing .

Good pressure means nothing
What is your evaporation at the coolers.
What is the subcooling off the condenser

Lack of subcooling could also cause this, could be mostly gas going through the expansion valves not liquid.


Kind Regards Andy

[US Iceman]

MajinDave,

When you ask for help it would be nice to include some basic information for us so that we can understand your problem.

As Andy said, good pressure doesn't mean anything. What refrigerant are you using in this system? What is the suction pressure at the compressor?

I'm also questioning why the compressor is designed for -10C suction and the room is at +6C. That seems like a lot of difference!

If the evaporator coils were sized for a 6 degree temperature difference, that would still put the evaporating temperature at about 0C. At this temperature I doubt the coils would frost much anyway.

Is the problem new, or has it been going on for some time?

[MajinDave]

MajinDave,

When you ask for help it would be nice to include some basic information for us so that we can understand your problem.

As Andy said, good pressure doesn't mean anything. What refrigerant are you using in this system? What is the suction pressure at the compressor?

I'm also questioning why the compressor is designed for -10C suction and the room is at +6C. That seems like a lot of difference!

If the evaporator coils were sized for a 6 degree temperature difference, that would still put the evaporating temperature at about 0C. At this temperature I doubt the coils would frost much anyway.

Is the problem new, or has it been going on for some time?

US Iceman

I'm using R-22 , the suction pressure is 1.6 bar , i was explaining that the room has to be cooled to 6* , and the compressor is 12kw at -10 , i'm using 1 compressor for 6 evaporators each ~ 3kw .
This has been going on for a month now , and the room's temp hardly drops below 16*

[frank]

US Iceman

I'm using R-22 , the suction pressure is 1.6 bar , i was explaining that the room has to be cooled to 6* , and the compressor is 12kw at -10 , i'm using 1 compressor for 6 evaporators each ~ 3kw .
This has been going on for a month now , and the room's temp hardly drops below 16*

Obviously a mis-matched system. 6 x 3kw evaporators = 18kw indoor load connected to a 12kw compressor

[Peter_1]

Make a little sketch of the setup and post it here.
Length and diameters lines, what valves and orifice, type of evaporators, type of compressor, (1 TEV) condensor, measured pressures, ....

[US Iceman]

For a system using R-22 and a suction pressure of 1.6 bar (I'm assuming gauge pressure) the saturation temperature for that pressure is -18.3C.

Something is not right. Besides the comment Frank added too (which bothered me also).

Did the lack of cooling start when the weather started to get warmer?

With 150 meters of refrigerant tubing, my guess would be the liquid line has a lot of flash gas in it, reducing the system capacity.

Does the liquid line travel up to the evaporators? How high does the liquid line go?
Does the liquid line travel through a hot space before reaching the evaporators?

[juandeloscabos]

we need to know if every thing match.....
compressor model.......
amps, voltage and phases......
evaporator model.......
TXV number.............
refrigerant pressures.....
discharge.....
suction.......
pipe temperatures at low side...
subcoolong and superheat....