HELP!!! CGAC Trane

[cheesetech]

Guys what a great night here in N.IL. We are working on a CGACD121RLNLL603ADFGWR Trane Chiller. It will run about 20 mins and then trips out with a LTC Cutout. We assume this means Low Temp Cutout, but we can figure out why cause the temp entering the machine is 100 degrees. and the temp leaving is around 70. Please call me with any advice you may have. And of course we don't have a tech book for this machine so we r up a creek without a paddle.

Matt - 815-543-1476

If you respond to this I won't get it because I will be " up on the roof" working on this stupid thing.

Thanks

[mustardman]

How about bad sensor anyone?????

[Dallas Duster]

How about low flow

[mustardman]

I figured someone would chime in with that one next.

[cheesetech]

We r getting plenty of flow, 375GPM we r thinking about the sensor, but with out a book we don't know where to look!!!! LOL

[the007]

3 to peek at...the leaving chilled water sensor usually right at barrel, the saturated evap sensor on bottom of evap barrel and the last is suction temp sensor in the suction line just a foot or two from the compressor. most of these are paired up, like leaving and entering chilled water sensors, etc. i would for shoots and grins watch the unload solenoids to make sure it's doing that too. best of it.....

[mike robinson]

Iam asuming you are talking about entering water and leaving water you must have a heck of a load on this machine what is this chiller trying to cool?

[Dallas Duster]

How are you checking your flow? a 30F delta t can`t be a good thing .What are the pressure readings?

[CVHCR1]

I assume that your packaged chiller has a w7900 leaving water control. You must be reading the light pattern for the LTC trip diagnostic. If you suspect the sensor, disconnect it and ohm it. Typically the sensor should read 3,400 ohms at 70 degrees, 100 degree water entering should give you over 3,600 ohms. If you find the sensor to be reading correctly, put it back in the well and ohm the wires to ground. There should be no reading. Also you MUST have GOOD thermal conductivity between the well and the bulb or weird things can happen That control will "load limit the machine until you have a 56 degree leaving water temperature. This will limit the compressors from loading too far, so I doubt that your actually hitting the freeze trippoint, especially with that kind of water temp. The w7900 control doesn't do anything fast. The second light will light up for a four minute time period on repowering the circuit. The chiller is designed for a 10 degee delta T. I also think that you need to check your flow. You need between 144 and 420 gpm for that machine. CHECK THE FLOW AGAIN!

[cheesetech]

right now the chiller isn't trying to chill anything except the water that is in teh system. 30% Glycol 70% Water. Once the temp comes down, the chiller will be cooling latte coffee mix. The computer observation system we have in place, shows that the entering temp of water is 100.8 degrees and leaving temp is 100.6 with out the chiller running. When the chiller kicks in it is pulling 60amps on one compressor. The secondary compressor doesn't seem to kick in. The machine will run for about 5 minutes then stop. At that point the temp entering the chiller is 98.5 and leaving is about 92. The pressure in the supply line is 50 PSI. And we have no reading for the return line pressure.

[cheesetech]

The flow is going well. We just double checked the flow. It is still at 325 gpm. I will go ohm the sensor, but i don't know where to find it at????? This may be a stupid question but so far u guys are being VERY HELPFUL and I doubt you won't mind answering this question..... Thanks Again.

[referteacher]

You're stacking the refrigerant in the condensr !!!!!!!! It's considerably colder in Northern Illinois tonight than 100 degree water you have going in that chiller. With the refrigerant stacking in the condenser, the suction side is starved and suction pressue goes w-a-y down. You DO have guages on the system, don't you. The low (refrigerant) temperature control senses the suction pressure and uses temperature/temperature relationship you conclude it's tripping on low temperature. It has a time delay on startup to give the system time to build up enough head to push the liquid out of the condenser through the expansion valve.

You gotta try to get the discharge pressure up AND the incoming water temperature down. Can you kill some (or all) the condenser fans? You may even have to block off some of the condenser coils in that "Windy City". Can you someway get cooler water in the system? Shut down all the processes and/or air handlers. Throttle the water down? You may need to temporarily jumper the flow switch. Make sure you have help keeping an eye on everything until you get the system "right side up". There's a lot of things going on at the same time you need to keep an eye on.

I know how you're feeling . Been there done that many times. We called it "Baby-Sitting"

[mustardman]

As good listener asked how are you checking your flow. What is your pressure drop across the chiller and have you plotted it on the graph specific to the machine. Referteacher has a good point. What do your guages say refrigerant that is. A little more info and we can help you.