criosbanc problem

Hi evreyone,

I'm having a few problems with a customers fridge, it is a criosbanc cabinet witha partially destroyed I.D plate, all I can get is a model which I think is D1A41 and a cond unit which is a Asprea model UT2178GK. The system runs on R404a and the customer assures me that the other engineer that has attented quite a few times recently has been adding refrigerant. When I connect my guages the suction press is just over 5 bar and the liquid press is 27 bar, the ambient temp is around 24 degrees c, the condenser is clear, liquid line burning hot, system has a 12ft long blower evap with a number 2 orifice, it has also bubbles in the sight glass, I dont want to add anymore refrigerant due to high liquid press, but I cant remove the current charge and recharge because I dont have a charging weight on the I.D plate can anyone please help, thanks. Alex Boyd:confused:

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Originally Posted by acb

Hi evreyone,

I'm having a few problems with a customers fridge, it is a criosbanc cabinet witha partially destroyed I.D plate, all I can get is a model which I think is D1A41 and a cond unit which is a Asprea model UT2178GK. The system runs on R404a and the customer assures me that the other engineer that has attented quite a few times recently has been adding refrigerant. When I connect my guages the suction press is just over 5 bar and the liquid press is 27 bar, the ambient temp is around 24 degrees c, the condenser is clear, liquid line burning hot, system has a 12ft long blower evap with a number 2 orifice, it has also bubbles in the sight glass, I dont want to add anymore refrigerant due to high liquid press, but I cant remove the current charge and recharge because I dont have a charging weight on the I.D plate can anyone please help, thanks. Alex Boyd:confused:

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Hi Alex:)

Seems it's a little overcharged.

Decant all to a cylinder (vac it out and use this to suck the charge in)

Then recharge be measuring the suction superheat and the liquid subcool of the condenser.
2 to 4 sub cooling and 10k superheat if it is a capillary and an average of 6k if it is an expansion valve.

Remeber someone did exactly this in the first place to come up with a charge.

Best change the drier;) that may have been the problem all along.

Kind Regards Andy:)

Hi Andy,:)

Thanks very much for that, but please forgive my ignorance, when you measure the superheat and subcooling do you mean with a thermometer on the inlet and outlet to get this, and what do you mean by 10k, this is something ive not had to think about in my normal day to day since leaving college.

ever so humble Alex:o

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Decant all to a cylinder (vac it out and use this to suck the charge in)

Then recharge be measuring the suction superheat and the liquid subcool of the condenser.
2 to 4 sub cooling and 10k superheat if it is a capillary and an average of 6k if it is an expansion valve.

Remeber someone did exactly this in the first place to come up with a charge.

Best change the drier that may have been the problem all along.

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This is some of the most cogent advice I have seen regarding cap tube and TEV self-contained systems. Good job Andy. You will certainly avoid overcharging the system with this advice. I have seen new equipment with higher subcooling values, but this is a great beginning point as we watch the balancing act.

Alex, if you have a pressure tap available where you can read the pressure, then use the pressure to determine the saturated temperature and a thermometer to measure the superheat at the outlet of the evaporator, and a thermometer to measure the subcooling at the outlet of the condenser. If you do not have pressure taps available, pick the middle of either coil to ascertain the saturated temperature with a thermometer, and then a thermometer at the outlets of the coils.

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Originally Posted by acb

Hi Andy,:)

Thanks very much for that, but please forgive my ignorance, when you measure the superheat and subcooling do you mean with a thermometer on the inlet and outlet to get this, and what do you mean by 10k, this is something ive not had to think about in my normal day to day since leaving college.

ever so humble Alex:o

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Hi Alex:)
If your condensing unit shows -10 deg c on the suction gauge (fitted at the compressor) subtract say 2k, this will give you the evaporation temperature of a resonably well design system (the 2k subtracted is the pressure drop in the suction line converted to a temperature loss)
This gives you an evaporation temperature at the evaporator outlet of -8 deg c. Now 10k superheat added to this would be a suction line at the evaporator outlet of 2 deg c, measured with a thermometer. Remember the temperature measured at the compressor on the suction will be higher and will vary too much to be any use to you; measure at the evaporator outlet only.

Subcool is similar. Look at you head gauge, read of the pressure (you can fit a pressure tap valve at the liquid connection off the condenser).
It may read 40 deg c, 4k subcooling would be a thermometer reading of 36 deg c. Matter what it reads deduct 4k and you have 4k subcooling.

Hope this helps:)
Kind Regards Andy:)