problems with a 230ton york air cooled screw 1

[joeywpittman]

I’m having problems with a YORK 230 ton air cooled screw machine.
M/N:YCAS0230EC46YFASB
Year:97
Roughly, for the past year, once every three months, it trips out ckt#2 with this fault message: “High DSCH Temp”. Now it is appearing more frequently.
According to troubleshooting guide in the maintenance manual, there are three things to look at: 1. Superheat is too high
2. Blocked air flow
3. Faulty sensor
We have checked all three areas, and they are all with in range
1. The superheat is normally 10-12 and 10-12 on the economizer
2. The condenser coils are clean as a whistle, with all 10 motors running properly
3. The sensors are on the money
We have tried other remedies:
1. Replacing the eprom on the processing board
2. Replacing the compressor’s oil filter
3. Adjusting the charge (removing gas, then adding gas)
4. The factory even came out and looked at it and they could not fix the problem.

This machine is one of three chillers all tied together to cool this facility


This is a link to the IOM

http://www.york.com/products/esg/ServiceLit/ywpubs/201.19-NM1.pdf

Can you give me any ideas of what we can do?

 

[sreid]

First, I'm not a HVAC guy but this seem to be an electrical troubleshooting problem. I would suspect an intermittant in the discharge temperature sensor/wiring/electrical interface. A momentary glitch here would cause the fault to be asserted. I'd first check the temperature at the discharge outlet with a temperature meter. You should also check that reading against the other two units to see if the temperature is indeed too hot. The manual said 127 deg C but this is probably the internal temperature. If the temperature appears to be OK i'd first check all the wiring and connectors in the discharge temperature string.

 

[imok2]

Have you ck the ground wire for good ground on the sensor

 

[joeywpittman]

last 6 history logs
1 2 3 4 5 6
Wed. Wed. Tues, Thrus. Thrus. Thrus.
May 26 May 26 May 20 May 20 May 20 May 20
12:47pm 12:01pm 2:11pm 2:14pm 2:09pm 1:47pm

Shutdown Fault
System #1 No Fault
System #2 High DSCH Temp.

Leaving Water Temp 44.5 42.9 44.9 47 43.2 42.9
Return Water Temp 47 45 47.9 48.3 45 44.7
Delta Temp 2.5 2.1 3 1.3 2.8 1.8
Ambient Air 93.6 91.3 93.1 91.8 91 91
Lead Sys. 2 2 2 2 2 2


Comp. #2 on on on on on on
Run time 43 min 4 hrs. 17 min 6 hrs. 46 min 2 ins 19 min 3 hrs. 6 min.
FLA 56% 56% 57% 56% 56% 55%

Oil Pres. 220 216 221 220 214 211
Suction Pres. 66 64 68 67 64 63
Discharge Pres. 244 240 245 243 236 234

Oil Temp. 186 181 183 186 184 185
Suction Temp. 46 44 47 47 44 44
Discharge Temp. 260.3 260.2 260.1 260.3 260.2 260

Sat. Suct Temp. 38.6 36.9 39.8 39.2 36.9 36.5
Suct Superheat 8 7.8 7.6 8.4 7.3 7.5
Sat. Disc Temp. 115.4 114.3 115.8 115.2 113.7 112.5
Disc Superheat 144.7 145.8 144.5 145 146.5 147.6

Slide Valve Step 48 12 75 75 14 18
Economizer off off off off off off
# of Fans 2 2 2 2 2 2

 

[sreid]

Well the log says the discharge temperature is at the limit. The question is, is it true? I still recomend you measure the discrarge temperature especially comparing it to the other running units.

 

[satur]

Did you get an answer to your problem? Shouldn't the economiser be energised at this loading stage?

 

[imok2]

It sounds like all the cond fans are running in reverse rotation are they 3 phase? If so reverse and 2 of 3 leads

 

[joeywpittman]

we fixed the problem.
the hydraulic 3 way valve ,which loads and unloads the compressor,was sticking.
we replace part and the machine is now running properly

 

[imok2]

Way to go Joey and thanks for letting us know the soution