City multi water cooled- not cooling

[garboy]

Hi All, I'm looking at a city multi PQRY p250ymfc. Water cooled, the condense water is perfect @26 degrees,The compressor runs and pumps, as far as I know it's correctly charged, and there is definitely no leak in the system.
The problem is that no matter how many units are on cooling the compressor rarely goes above 30hz. This results in poor cooling to 7 of the 9 cassettes. The discharge temps is about 80 and suction ins fine. The super heat at the indoors is 15-29 degrees! With no cooling. I'm starting to loose patience, all or any ideas would be ggreat gar

[install monkey]

any fault codes ?- whats it do in heating??

[The Viking]

First of all it is worth checking the pressures, as you got your gauges on the system do check that the system reads the same pressure in the controls as you got on your gauges.
After that it is pretty much a game of "follow the temperature", trying to ascertain where the refrigerant flows.

One thought that strikes me after reading your post, especially the bit about the charge, "assume, that makes an ass out of u & me"...
Any problems like this on any VRV/VRF system and the starting point of the troubleshooting must be to verify the charge. A quick reclaim down to just above 0 soon tell you and as you haven't introduced any impurities to the system you don't even need to vacc it before you recharge it (providing you got the right charge out of course). Unless you installed and commissioned it yourself it is also worth checking the charge calculations.

Happy hunting!



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[garboy]

The gauge pressure and the pressure the system is reading are the same. I know the charge because we reclaimed all the gas to do a full pressure test. It dose the same in heating too, good heat from 2 maybe 3 cassettes- but not great maybe 30 degrees.

[garboy]

P.s no fault codes showing at all.

[install monkey]

http://www.mediafire.com/download/3m...e_Handbook.pdf
happy reading

[Neddy]

Crossed pipes? Incorrect port settings? Has it worked in the past? Do a full LEV reset on all units.are the sensors on the heat plate exchanger reading correctly?

[garboy]

Hi all,just to let you know it looks like the problem was the thermistor for the suction temp. It was very slightly out of calibration, it was reading -5.5 when it should have been about - 2.0, when i swapped it the compressor ramped up to 90hz!