Trane Chilled Water Package

Hi,

I have a Trane Helirotor Compressor package running on Chilled Water @ 6 degrees

There are two compressors but run two seperate circuits,
Circuit two keeps going out on ''LOW DIFFERENTIAL PRESSURE''
the suction pressure is 2.5BAR
Discharge pressure is 5 BAR,

In the Manual it says the 'if the pressure is 2.5 bar or less for more than two minutes it shuts the compressor off,
Can anyone tell me if this is the differential pressure between suction discharge?, as the other circuits runs well and discharge pressure is normally 8 BAR ..

Any idea's /regards

Brendan

I've only worked on a fairly large Trane unit, ERTHC..
What refrigerant is this on R134a? I've had a call of a simular situation, where the compressor was tripping on L.P. This was due to some if not all of the oil from the oil sump ending up in the evaporator due to this circuit running unloaded for some time, thus pushing the oil into the evaporator and then tripping on L.P. with the Oil level sensor reading Dry not wet..in the service mode.
You need to prime the oil return line where there is a optical sensor and then run the compressor fully loaded if possible to get all of the oil back this then should clear the problem.
Only a thought..

Thanks Thana,

Looking at the 'faults manual' it says that pressure is less than 2.5 bar for more than two minutes it cuts out,
I possibly thought it could be a faulty discharge pressure transducer that gives you the condensing pressure, this transducers also controls the vsd fans,

I put my gauges on the inlet to the condensor (on main header) and had 7.5 BAR, whilst on the PLC (controler) it was reading 5 BAR,

where the pressure transducers is located on the condensor is at the outlet, is it possible to have a 2.5 pressure drop between the inlet and outlet?

(also would overcharged system cause such a low discharge pressure)? i would imagine this would not be the case..

Regards

Brendan

What's your oil pressure?

Chris

Well a over charged system would not give you a low discharge pressure it well may give you a higher discharge temperature though.. Is it going to load when it trips? Try an amprope on the compressor to see what it's pulling. Becarefull of the sensors on the display screen as these may well be saturated gas sensors so maybe it's good to use your gauges instead..

The unit normally measures the saturated condensing pressure less the saturated evaporator pressure taken from the sensors. If the sensors are out of spec, then you will get problems. The 'Low diff ' trip comes from the fan staging control setup that monitors cond fan requirements for a stable head pressure. As Thana says, check that the unit is loading (Current increase on load up)Check the load/unload solenoids are operating correctly, if this is the model I'm thinking of you should have a female rotor sol valve (on/off) and 2 male rotor valves that allow the slide valve to load/unload via oil pressure. Check that the valves are operating, if not when you start the compressor, all you get is two rotors turning and no press diff to speak of. LOL, Danny.

You may find that the problem is oil pressure differential. The compressor will start up and run for two or so minuites before the oil pressure has built up enough for the oil pressure switch not to trip, you need to check the oil pressure against the suction pressure to see what the difference is, and check the oil pressure switch setting to make sure it's not operating outside of its range. There may also be a winter start kit fitted, which basically bypasses the LP switch for a determined time, this can be up to 10mins. This is usually only fitted where a low ambient is possible.
The water temperature can also affect the suction pressure, check the water strainer. Andy C.

Thanks guys

Appreciate your help,

Quote:

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Originally Posted by dannyd

Check that the valves are operating, if not when you start the compressor, all you get is two rotors turning and no press diff to speak of. LOL, Danny.

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Even completly unloaded the pressure difference will higher then 2,5 bar.

Check and see if the condensation sensor is out of range. But usually this generates a oil loss/ oil flow alarm or causes the machine to limit on high pressure.

What machine is it?

its a Trane Helirotor Screw Compressor , sorry don't have model details with me,
Its controlled off a Trane UCM-CLD ,

Approx 4 years old,

I suspect either a faulty pressure transducer or a the vsd fan settings are wrong, where the fans are cycling on when not required

does anyone know the password to change operators settings ?

The password should be in the manual on that one I think. I suspect it's an RTAB or D as the RTAC has a CH530 controller.
As Lowrider says, the PD should be comfortably higher than 2.5Bar at any stage of duty.
Check the sensors & evap. water temps as has been suggested, using your equipment to verify the machine's probes.

The passwords are not in the manual, you'll have to get Trane to the job, there are many more settings with which you can harm the machine so I can't give it!

Quote:

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Originally Posted by Lowrider

The passwords are not in the manual, you'll have to get Trane to the job, there are many more settings with which you can harm the machine so I can't give it!

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The factory ones aren't, but he asked for the operator password. ;)
Although thinking about it (it is a while since I worked on a UCM-CLD) the operator section is not going to be much help to him, is it? :(

And it's true, without the specialist knowledge you can do a lot of harm by messing with the factory settings without a full understanding of what they mean.
The CLD part of the controller name stands for Clear Language Display - but that doesn't mean what it displays makes sense. ;)

a pssword is only needed for the service setup menu and the machine configuration! And that's where all the settings are that can really harm the machine!

So all I can say, again, is call Trane!

Hi Guys.
Most of the passwords ++--++,+-+-+- n enter
Just play around with the plus minus signs and you'll get the hang of it. This passwords apply to the UCP2.
UCP1, UCM, CH530 does not apply.