View Full Version : Cold display case... hot new compressor

28-10-2014, 02:16 AM
Hi, to you all.
Display case, a 10th or more years, R22 system on a 1HP condenser. 220V on a monofasic. The condenser is on the first floor around a 3.5M above the displaycase.

So long story short... A client call me his display case wasnt cooling, so we check the condenser... someone bridge the low pressure protection, an pipe got a fiction hole and loose all the gas, the compressor burnout. The system is running or R22

We changue the compressor, the low pressure protection, the filter dryer. And turn on the equipment, the first pressures was arround LP 30Psi, HP 150Psi.

So we let it for around 1 hr and the compressor gets really hot... We take all the numbers witch are;

LP 175Psi Temp. 34.4C
HP 30Psi Temp. 18.0C
Comp. Amp 5.09A / 7.5A
Cond Air In. 20.1C
Cond Air Out 30.8C
Superheat 32.2C
Subcooling 0.6C

So far, the main problem was there was almost not cold in to the suction line to refrigerate the compressor, and causing it to raise is temp. After an hours to be runnig the compressor reach 80C file:///C:/Users/ALEJAN~1/AppData/Local/Temp/msohtmlclip1/01/clip_image001.png

Following a chart, we found a very like failure may be the TXV, so we go there and changue it, and old Alco, for a new Danfoss No.2 Oriffice.
We add some refrigerant ang get this more likely numbers;

The design of the evaporator is a giant coil of copper tube of 5/8, in the floor of the cold display, then a axial fans move the air inside.
11816 11815

The new set of numbers;
LP 180Psi Temp. 33C
HP 35Psi Temp. -1.3C
Comp. Amp 5.7A / 7.5A
Cond Air In. 24C
Cond Air Out 30.C
Superheat -8.7C
Subcooling 1.8C

I have instaled coldrooms and in those when the compressor start the cycle and in the sigth glass, its easy to see the liquid refrigerant moving ahmm to lack of an clearly explanation, fast, or with speed, on this particular system, the sigthglass do show liquid moving, but is more like an slow stream. ???

At this point the compressor is getting some cold of the succion line, the pipe sweat and even gets frosty at the end of the cycle, how ever Im concern because the compressor is reaching 42C and I think is execesive for a brand new compressor.:(:(:(

Any tougths on this?

im thinking on changue to a #3 oriffice, to allow more refrigerant to flood the coil, maybe add some liquid to the system to reach the same pressures.

28-10-2014, 01:19 PM
Maybe put it on 134a,vacuum and change the valve and drier if it's a new compressor it should have the correct oil for 134a but check!

28-10-2014, 05:05 PM
Maybe put it on 134a,vacuum and change the valve and drier if it's a new compressor it should have the correct oil for 134a but check!

134 has lower capacity, about 30% so nothing will work well.

Alex, make sure suction line is well insulated, you can also insulate the accumulator .
Try to adjust the superheat that more refrigerant will flow into the evaporator. From the picture I can see that you did not open the inlet of the txv to clean the inlet filter, it could be half blocked.

Something is not right with your numbers, 35 psi using 22 is -11C so I take it that whatever you measure temp with is not good.

Once you have checked that all components preform well, adjust the TXV so suction line will sweat up to the compressor.

28-10-2014, 07:47 PM

29-10-2014, 05:43 AM
Hi, thanks for the reply, muy bad thath was tge old expansion valve, and I changed for a brand new danfoss r22,expansin valve.
When the cycle starts the pipes are dry, but , near the enss of the cycle, the suction wets, then chill and then frosty.
Now for the temperature, yes in deed.is an odd and wrong to pt chart, however I use the same thermocouple for the high and low side, Just order a new double meter, but untill then.... I will follow your advice, to open the valve to allow more liquid, or even change the oriffice, and will come back to post the results.


31-10-2014, 01:43 AM
Hi, Its me again...

So we whent down to see the cold display, the same story, the compressor was at 42C:(, way too much for a cold mornign here.

So, capture gas on the liquid reservoir, open the system, changue the TXV danfoss orifice #2, for a #3... vaccum the lines, pressure test... Switch on...

The system start on the same relative pressures, but this time, wets more cool on the suction side line, to be accurate... the compressor it was at 30C on the hottest spot, have a litte bit of frost on the suction line and the head, but no problem, has an liquid trap...

So now it is nice and cool ;)
so... keep it frosty :D