flyboy3b
29-09-2007, 03:08 PM
ill try to make this as short as possible, and thanks for reading.
i bought a used norlake that is claimed to have a bad compressor. my first check found low enough pressure that i had to lower the low pressure limit to get it to fire up. there were no useable reading to be taken at that time.
i charged it with 70 lbs nitrogen and found a leak in the evap coil which i repaired. i refilled it and left it for a few days and it held pressure.
when i returned, i evacuated the system to 500 microns, and started adding a charge of 404a.
the nameplate reads 42 0z as a reccomended charge, but i dont know if that is the original condensing unit, so i start adding refrigerant slowly and watch my gauges and thermometer readings. at one point, i see the evap coil frost up (a breif moment of elation) and i continue to slowly add the liquid. as i continue adding, i see the coil warm up and sweat and when i reach 42 oz,, i stop.
at this point, i have the following readings;
1. ambient 76 (it was a nice day in wisconsin)
2. full load on the coil (this unit is self contained and its just sitting on the floor)
3. temp after the reciever 97
4. pressure after the reciever 275 lbs
5. low side 75 (at the compressor)
6. temp at the low side of compressor 86.6
7. temp at the entrance of the evaporator coil 48
8. temp at the evap outlet 56
ok,, so the subcooling looks ok, but the superheat is really high, and the coil is not getting cold enough. so i pull 12 oz out of the system and the high side pressure drops to 200 and the amount of subcooling drops to 7 Deg. the superheat drops a little, and the first couple runs on the evap coil ice up, but overall,, still not cold enough.
i try adding 28 oz of refrigerant (16 oz more than the nameplate) still no noticeable difference. the high side pressure stays at about 280, the subcooling is around 10 deg, the superheat is high, and not much cold air
with a 16oz overcharge (supposedly) the system has the following readings;
1. evap outlet temp 56
2. compressor in temp 75
3. compressor in pressure 75
4. condensor in temp 125
5. condensor out temp 98
6. pressure after the reciever 280
7. no noticeable temp change at the drier
8. appears to have a new txv (which i tried adjust with no appreciable difference).
the compressor is an extended medium temp application and everything else appears ok.
any thoughts on this would be greatly appreciated. fortunately, this is a spare walkin and it doesnt need to go into service right away, but ive been spending alot of hours trying to figure this thing out (its my first system).
thanks again in advance,
mike
i bought a used norlake that is claimed to have a bad compressor. my first check found low enough pressure that i had to lower the low pressure limit to get it to fire up. there were no useable reading to be taken at that time.
i charged it with 70 lbs nitrogen and found a leak in the evap coil which i repaired. i refilled it and left it for a few days and it held pressure.
when i returned, i evacuated the system to 500 microns, and started adding a charge of 404a.
the nameplate reads 42 0z as a reccomended charge, but i dont know if that is the original condensing unit, so i start adding refrigerant slowly and watch my gauges and thermometer readings. at one point, i see the evap coil frost up (a breif moment of elation) and i continue to slowly add the liquid. as i continue adding, i see the coil warm up and sweat and when i reach 42 oz,, i stop.
at this point, i have the following readings;
1. ambient 76 (it was a nice day in wisconsin)
2. full load on the coil (this unit is self contained and its just sitting on the floor)
3. temp after the reciever 97
4. pressure after the reciever 275 lbs
5. low side 75 (at the compressor)
6. temp at the low side of compressor 86.6
7. temp at the entrance of the evaporator coil 48
8. temp at the evap outlet 56
ok,, so the subcooling looks ok, but the superheat is really high, and the coil is not getting cold enough. so i pull 12 oz out of the system and the high side pressure drops to 200 and the amount of subcooling drops to 7 Deg. the superheat drops a little, and the first couple runs on the evap coil ice up, but overall,, still not cold enough.
i try adding 28 oz of refrigerant (16 oz more than the nameplate) still no noticeable difference. the high side pressure stays at about 280, the subcooling is around 10 deg, the superheat is high, and not much cold air
with a 16oz overcharge (supposedly) the system has the following readings;
1. evap outlet temp 56
2. compressor in temp 75
3. compressor in pressure 75
4. condensor in temp 125
5. condensor out temp 98
6. pressure after the reciever 280
7. no noticeable temp change at the drier
8. appears to have a new txv (which i tried adjust with no appreciable difference).
the compressor is an extended medium temp application and everything else appears ok.
any thoughts on this would be greatly appreciated. fortunately, this is a spare walkin and it doesnt need to go into service right away, but ive been spending alot of hours trying to figure this thing out (its my first system).
thanks again in advance,
mike