Help required - York chiller YDAJ77

[scutworth]

We have developed a problem with our YDAJ77XT9 York Millenium Recip chiller system. We currently operate only systems 1 & 2 (systems 3 and 4 have been out of action for years, but we don't need more than two systems).

Our setpoint for water leaving temp is -5C (30% glycol), but we are unable to achieve it because system 2 will not kick in. When system 1 runs as lead compressor (normal operation), we get a "NO COOLING LOAD" message and the system refuses to start then gives us a low oil pressure error. We changed the lead to system 2 to see what would happen and it again refused to start, giving a low oil pressure message. System 1 started shortly afterwards. Systems 1's pressure look to be fine, but system 2 is obviously not giving us anything useful as it is not starting. I believe that the solenoid activates, but the compressor doesn't receive the start signal.

Our service engineers seem to think the problem is related to one of the circuit boards, but our control engineer is convinced that the compressor itself is the problem. If it is indeed the circuit board, we don't know how to determine whether it is the main EPROM board or one of the subsidiary boards.

Can anyone offer any advice as to likely cause, possible solutions and, if the boards are the problem, how to diagnose which one it is?

Thanks in advance.

[yorkie10]

The history buffer is a good place to start, is the compressor actually starting, if the micro controller outputs a start signal to the compressor it looks for a current feedback > 7A and an oil PD > 2Barg within 30 secs. The micro outputs to a relay card mounted adjacent to the comp contactors, these do have a tendancy to arc so may be an idea to check these as well.

[Yuri B.]

we get a "NO COOLING LOAD" message and the system refuses to start then gives us a low oil pressure error.

Which messages inbetween these two? Microprocessor should first sense no current to the motor with oil diff control only starting after 10sec of the compressor's motor succesfull start and work. Is there no CT(s) on this model?

[yorkie10]

Hi Yuri, many thanks for correcting my timing mistake.
As one of the old York factory boys I worked on the YCAJ / YDAJ assembly line with all European designated chillers, (those built in the Basildon factory) all having CT(s) fitted.
We did have a couple of USA built units come through that didn't have CTs' installed but these went to the far east, (no BS or CE certification).

[RAVISEKAR]

Hi scut,this chiller is a master and slave model,check your rate of sensitivity default try to adjust the temprature weather can run the system if this system run try to rectify low oil pressure problem weather need to do overhaul compressor