York YCAF sensor problems

[R 22]

Hi all,
Can anyone help me with the following problem on a 1994 York YCAF single circuit water chiller?

The unit will start up fine, but after a time (more often than not 16 minutes) stop with the message "LWT (leaving water temp) sensor fault". It then starts up again after the recycle time and does the same again, locking out after the third attempt. I know that the sensor and it's wiring back to the board are not the problem. I removed the sensor and put in a resistor of suitable value to make the unit think the water was at 16 deg. C. I also put in a new piece of cable from the sensor to the board. I have also changed the control board with one salvaged from a scrap twin-circuit unit after swapping the EPROM and RAM chips. All to no avail. HELP!

[Brian_UK]

HI and welcome to the forum.
Not sure about this particular chiller but what is the actual water temperature at the time ?

Sometimes two faults can trigger the same fault code.

Is the machine hitting minimum water temperature and going for freeze protection ??

[al]

on start up these older chillers take lwt and compare it to suction temp i think, if the difference is too large then it faults with lwt fault. check gas and water flow rates are ok, ie could be blocked water filter or gas leak.

also if water temp is too high then this results in lwt fault showing.

al

[al]

Check eeprom is right way up with all prongs inserted!!
also i had previous probs with 5vdc being dragged down by an intermittant fault on the oil sensor.....keep us informed!

al

[coolerman]

braın abi ben tr den erol dilimi anlarmısın bilmiyorum ama Allah senden razı olsun.Sayende york chilleri çözdüm.lwt sensör fault artık tarih oldu kendine çok iyi bak bana yazarsan sevinirim abi....

[absrbrtek]

Change it to return water control. al is correct in his diagnosis. You will also find the start to run time is a excessively high ratio. Seen this before return water sensing solved the problem.

[R 22]

Thanks Gents for your replies.

To continue, leaving water temp is about 17 C, so no danger of frost protection. Plenty of water flow as well. Pressures are 3.5 bar suct. 17.5 disch. (R 22) Strangely for a York, the unit does not have an inlet water temp sensor. Nor does it have gas temperature sensors, only pressures. So changing to return temp control is out. Haven't checked 5v yet, but I will.

However, there has been another development. The chiller is connected to a large (90,000 litre) tank, so any temperature changes happen very slowly. It's quite cool today (7 C) so I took the LWT sensor out of it's hole and left it dangling in free air and set the unit to 4 C. Now the thing has been running for 4 hours without stopping. Al is indeed correct. Why does it think that 17 C is too hot? What kind of strange York logic is this? At what point does it think the water is cool enough to continue?

[1torr]

Hi, just a quick thought, 3.5 bar r22 is evaperating at below freezing(sorry no comparitor handy)at 17 deg c I would expect a lot higher suction pressure.SOG or starving tev perhaps? All the best, Kev.