AlexLPD
11-08-2015, 08:20 PM
Hi, first of all thanks for the comments.
Description of the system.-
This is a 3HP coppeland condensing unit running on a 5 fans low profile Bohn, evaporator. The TXV is a donfoss, the orifice was a #4. The unit uses a 3PH 3HP 220V compressor.
This is a bread cold room used to keep the bread before the baking. (Desire temperature from the costumer is 4-5°C)
The unit burn out a compressor, the client contract some one else to change it... We arrive at the scene because the compressor, don't start... The reason a damage low pressure protection, after this, we check the refrigerant and was none on the system.
The work was done on the system.-
The following procedure was make in order to fix the condenser;
1.- Chargue 350Psi of N2 to search the leak
2.- A broken nut on the txv was the leak. we Changue it and make a new fitting.
3.- We changue the liquid filter for a new one.
4.- Add a suction filter to the low side of the compressor.
5.-Change the sight glass, were too dark.
6.- Re- test on 350Psi of N2... The system hold its.
7.- We make vacuum on both sides of the unit (Also energize the solenoid)
8.- Re fill the system with brand new R-22.
--Clean the condenser coil--
Now the problem being.-
The compressor runs very hot, the evap temp is very high.
The pressures was nearly ok, but wasn't any return of cold to the compressor on the suction side, the air depleted of the condenser is 40°C, and the lowest temperature on the evaporator was around 11°C... so... we play a litte bit with the refrigerant charge but nothing... After changing the #4 for the #5 orifice of the TXV.
Nothing happens to the head pressures, so... the metering device wasnt opening or closing, the same pressure on the beginning of the cycle (even the chiller was warm some like 20°C) to the lowest temperature we can achive... (some near 14°C)
So, I change the TXV for a brand new danfoss, and leave the #4 orifice, now we can see some variation of the suction pressure, around 55Psi on the beginning and 45 at the lowest temperature we can achive at the time (Around 11°C on the out of the evap and 13° on the chiller).
The last data is;
REAL
REAL
CHART
PRESSURE
TEMP
TEMP
LOW SIDE
40
Psi
107
°F
18
°F
89
°F
OVERHEATING
HIG SIDE
200
Psi
107
°F
100
°F
7
°F
SUBCOOLING
So, the issue is a high overheating If i not made a lots of typos, but cheeking the list of the possible causes;
http://heatingandaircoolingrepairsdotcom.files.wordpress.com/2013/07/20130729-200951.jpg
Dont have a scenario when normal subcooling, higgh superheating, and normal low and high pressures.
Even so, the possibles scenarios are;
Low charge (The amp of the compressor is on the limit with 8.9A)
Low air flow on condenser ( Was clean recently)
Server restriction on with excess chargue (???)
Liquid refrigerant mild restriction. (????)
So, I might be looking for a bend on the liquid line and I have an overcharge...
Now I now many of you will need more data, I will provide as soon I can...
But for the sake of the tech visit, can you provide with some other possibles causes? or field experience?
Thanks a lot.
Kind Regards.
-Alex.
Description of the system.-
This is a 3HP coppeland condensing unit running on a 5 fans low profile Bohn, evaporator. The TXV is a donfoss, the orifice was a #4. The unit uses a 3PH 3HP 220V compressor.
This is a bread cold room used to keep the bread before the baking. (Desire temperature from the costumer is 4-5°C)
The unit burn out a compressor, the client contract some one else to change it... We arrive at the scene because the compressor, don't start... The reason a damage low pressure protection, after this, we check the refrigerant and was none on the system.
The work was done on the system.-
The following procedure was make in order to fix the condenser;
1.- Chargue 350Psi of N2 to search the leak
2.- A broken nut on the txv was the leak. we Changue it and make a new fitting.
3.- We changue the liquid filter for a new one.
4.- Add a suction filter to the low side of the compressor.
5.-Change the sight glass, were too dark.
6.- Re- test on 350Psi of N2... The system hold its.
7.- We make vacuum on both sides of the unit (Also energize the solenoid)
8.- Re fill the system with brand new R-22.
--Clean the condenser coil--
Now the problem being.-
The compressor runs very hot, the evap temp is very high.
The pressures was nearly ok, but wasn't any return of cold to the compressor on the suction side, the air depleted of the condenser is 40°C, and the lowest temperature on the evaporator was around 11°C... so... we play a litte bit with the refrigerant charge but nothing... After changing the #4 for the #5 orifice of the TXV.
Nothing happens to the head pressures, so... the metering device wasnt opening or closing, the same pressure on the beginning of the cycle (even the chiller was warm some like 20°C) to the lowest temperature we can achive... (some near 14°C)
So, I change the TXV for a brand new danfoss, and leave the #4 orifice, now we can see some variation of the suction pressure, around 55Psi on the beginning and 45 at the lowest temperature we can achive at the time (Around 11°C on the out of the evap and 13° on the chiller).
The last data is;
REAL
REAL
CHART
PRESSURE
TEMP
TEMP
LOW SIDE
40
Psi
107
°F
18
°F
89
°F
OVERHEATING
HIG SIDE
200
Psi
107
°F
100
°F
7
°F
SUBCOOLING
So, the issue is a high overheating If i not made a lots of typos, but cheeking the list of the possible causes;
http://heatingandaircoolingrepairsdotcom.files.wordpress.com/2013/07/20130729-200951.jpg
Dont have a scenario when normal subcooling, higgh superheating, and normal low and high pressures.
Even so, the possibles scenarios are;
Low charge (The amp of the compressor is on the limit with 8.9A)
Low air flow on condenser ( Was clean recently)
Server restriction on with excess chargue (???)
Liquid refrigerant mild restriction. (????)
So, I might be looking for a bend on the liquid line and I have an overcharge...
Now I now many of you will need more data, I will provide as soon I can...
But for the sake of the tech visit, can you provide with some other possibles causes? or field experience?
Thanks a lot.
Kind Regards.
-Alex.