need help on YORK chiller

[nassersh]

YORK chiller model YCAS0373 with 2 number DXS screw compressors.
The problem i have with one of the compressors is that it hunts while on load - i.e the suction pressure oscillates between 70 psi and 75 psi. Its not stable though its fully loaded with the sliding valve on step 75 indicating fully open and loaded. We never had any problem with it before, it all started after we carried out comprehansive service on it. The service included change of oil, change of core filters, vacuumed and refilled new refrigerant R22.

Readings from the compressor -

• <LI class=MsoNormal style="COLOR: navy; mso-list: l1 level1 lfo4">water in temperature – read from the thermometer on the water line to the chiller – 15 deg. C. Water out - read from the thermometer on the water line from the chiller – 7 deg.C <LI class=MsoNormal style="COLOR: navy; mso-list: l1 level1 lfo4">Suction pressure – read from the gauge – 72 - 74PSI; discharge pressure – read from the gauge – 205 - 210PSI
• Readings from the chiller panel

• <LI class=MsoNormal style="COLOR: navy; mso-list: l3 level1 lfo3">Oil – 12.7 BERG. SP -4.83; DP -14 BERG <LI class=MsoNormal style="COLOR: navy; mso-list: l3 level1 lfo3">Oil – 54.1 deg C. ST -11.4. DT -73.9 deg C <LI class=MsoNormal style="COLOR: navy; mso-list: l3 level1 lfo3">S1 SAT SUCT – 4.4. SUCT SHEAT – 7.2 deg C <LI class=MsoNormal style="COLOR: navy; mso-list: l3 level1 lfo3">S1 SAT DSCH – 39.3. DSCH SHEAT – 34.7 deg c
• Steps – 53

Any idea to how can i solve the hunting problem.

Thanks.

[Grizzly]

YORK chiller model YCAS0373 with 2 number DXS screw compressors.
The problem i have with one of the compressors is that it hunts while on load - i.e the suction pressure oscillates between 70 psi and 75 psi. Its not stable though its fully loaded with the sliding valve on step 75 indicating fully open and loaded. We never had any problem with it before, it all started after we carried out comprehansive service on it. The service included change of oil, change of core filters, vacuumed and refilled new refrigerant R22.




Readings from the compressor -

• <LI class=MsoNormal style="COLOR: navy; mso-list: l1 level1 lfo4">water in temperature – read from the thermometer on the water line to the chiller – 15 deg. C. Water out - read from the thermometer on the water line from the chiller – 7 deg.C <LI class=MsoNormal style="COLOR: navy; mso-list: l1 level1 lfo4">Suction pressure – read from the gauge – 72 - 74PSI; discharge pressure – read from the gauge – 205 - 210PSI
• Readings from the chiller panel

• <LI class=MsoNormal style="COLOR: navy; mso-list: l3 level1 lfo3">Oil – 12.7 BERG. SP -4.83; DP -14 BERG <LI class=MsoNormal style="COLOR: navy; mso-list: l3 level1 lfo3">Oil – 54.1 deg C. ST -11.4. DT -73.9 deg C <LI class=MsoNormal style="COLOR: navy; mso-list: l3 level1 lfo3">S1 SAT SUCT – 4.4. SUCT SHEAT – 7.2 deg C <LI class=MsoNormal style="COLOR: navy; mso-list: l3 level1 lfo3">S1 SAT DSCH – 39.3. DSCH SHEAT – 34.7 deg c
• Steps – 53

Any idea to how can i solve the hunting problem.

Thanks.

It sounds like a cassic case of hunting?
I might be wrong but please check....
Your expansion valve operation and Superheat
Grizzly
Just an additional thought someone hasn't managed to loose a liquid line filter felt gasket in the system have they?
It has been done before!

[ChillyWilley]

nassersh,

This maybe a stupid question, but are you sure this is not your economizer cycling?

[nassersh]

we dont have economiser on our chiller!

[ChillyWilley]

Re: need help on YORK chiller
we dont have economiser on our chiller! 10-12-2008 05:48 AM

I'm looking in FORM 201.18-NM2 IOM and it specs one for each system on your chiller. Check your TEV and refrigerant charge/subcooling.