CARRIER 30GTN025 PROBLEM

[nisong]

A CARRIER 30GTN025, KEEPS TRIPPING ON LOW PRESSUR IN WINTER(BELOW 20F) FOR THREE YEARS, BUT IT WAS ALWAYS FINE IN SUMMER. CHARGED FREON TILL SUCTION WAS ABOVE LPS CUTIN,BUT THE DISCHARGE TEMP BECAME TOO HIGH AND BURNED UNLOADER PLASTIC SHELL.

[matt8085]

Any low ambient controls on it?

[airworx]

you charge these systems by having the exv at a minimum 60 % fully open position, all compressors fully loaded and subcooling not by suction pressure that has nothing to do with it. the control modual will load and unload to get the presure and temps to design.

also for low ambient conditions motor masters are required
and condenser coil louvers in certain areas

[nisong]

has motormaster, nothing else.no hot gas bypass.
this unit is only 4 years old. this problem existed since it was installed.

[Edited by nisong on 01-15-2006 at 09:23 PM]

[airworx]

need ambient, chill water supply, return temp, discharge and suction preussre, subcooling and superheat, exv has to be a min. of 60% open.

[djken]

What error code are you getting??

[nisong]

ALARM CODE:A133. IT USES A TXV, NOT EXV.THE LIQUID LINE PRESSURE IS 300PSI,SUCTION LINE PRESSURE IS BELOW 40,OUTSIDE TEMP IS BELOW 20F,COOLER INLET WATER TEMP IS 60F. BEFORE THE MOTORMASTER COTROLED FAN STARTS TO RUN UP, IT TRIPS ON LOW SUCTION PRESSURE.

[Edited by nisong on 01-17-2006 at 08:26 AM]

[airworx]

cant give you a correct answere without subcooling and superheat. but sounds like restriction, with high head low suction but need sc and sh.

[djken]

Originally posted by nisong
this problem existed since it was installed.

I wish I had a quarter for every time I've been told that.
It sound like you've got a restriction somewhere. Make sure the charge is right, check the solenoid valve and check for temp. diff. across liquid drier. If those check out ok, I would suspect the TXV. Will it run long enough to check superheat?

[nisong]

CHECKED TODAY, FOUND THE MOTORMASTER BURNED, INSTALLED A NEW MOTORMASTER,P/N:32LT900300,BUT THE NEW MOTORMASTER DID
NOT SPEED THE FAN UP AT ALL, REMOVED THE NEW MOTORMASTER, SHORTED THE FAN CABLES, THE FAN RANS AT FULL SPEED.THE LEQUID LINE PRESSURE DROPPED TO ABOUT 150PIS, DISCHARGE PIPE BECAME NOT TOO HOT,THE SUCTION PRESSURE REMAINED THE SAME.ADJUSTED TXV COUNTER CLOCKWISE FOR ABOUT 4 TURNS, LOW SUCTION PRESSURE ALARM STILL HAPPEDNED SOMETIMES,BUT THE SUCTION PRESSURE INCREASED TO AROUND 50. THE OUTSIDE TEMP WAS BELOW 20F,INLET WATER TEMP WAS AROUND 55.
NEED MORE ADJUSTMENT?


[Edited by nisong on 01-18-2006 at 08:15 AM]

[coolairman]

Nisong:

Sometimes if you are running an air cooled package chiller, or any refrigeration system really, in ambient conditions below 20 F and the capillary tube on the low pressure safety switch is exposed to the ambient air the pressure in the capillary may drop and allow the LP switch to open.

You can remedy this by insulating the capillary tube.

Good luck.

Coolairman

[nisong]

THE LOW PRESSURE SWITCH IS INSTALLED DIRECTLY ON THE COMPRESSER,NO CAPILLARY.

[websy]

Just out of curiousity, did you install the new condensor sensor with the new motormaster(damn those things are pricey!). I changed one of these motormasters on a 30GTN030 last winter. I found it strange that it was operating two variable speed motors at 6.5 amps full load when the motormaster is only rated for 15 amp MAX continuous. Wonder why the fuses that come in the motormaster are 30 amp'ers. I installed some fuse blocks upstream of the motormaster and put some 15 amp fuses in. Guess what?? Multiple fuse replacments in a small period of time. When both motors are running close to minimum speed the amperage WILL spike above motormaster ratings. Just a little FYI. Carrier told me that the motormasters had to have been installed "aftermarket". I said BS its on the wiring diagram.