Chiller Controls Upgrade on a Hitachi Chiller
Job Description: Chiller Controls Upgrade on a Hitachi Chiller
Area: Bath Road, Slough
Issue Identified: Following a recent attendance on site ACES engineer advised that the chiller had faults, chiller 1 circuit 1 had no oil in the compressor, fan motor required replacing, refrigeration circuit required recovery and charge confirmation, low pressures on the circuits, possible EEV fault.
Controls Upgrade:
Our proposal offered a major cost saving over new equipment which will maximise the efficiency of the existing Chillers and will enable ‘open protocol’.
Additional benefits are:
Effective life cycle extension 2-5years + (this based on a strict maintenance and treatment plan and subject to new Refcom alteration plans)
Reduced energy requirement (circa 5 – 10% + power reduction)
Refrigeration system and Chiller control and mechanical Improvement
Minimal building disruption (chiller upgrade was carried out whilst keeping building operational. In addition to the above we installed Carel electronic expansion valve. This involved cutting the liquid line pipework and adjusting both the copper pipework and new EEV control wiring. Sizing and selection matched the duty range of the TEV’s
CONDENSER ASSEMBLIES
We modulated all condenser fan motors with the inverter controller, which received a 0-10v input from the new Chiller controls, based on the desired refrigerant head pressure control. The controller monitor’s the head pressure on both circuits and controls on the higher value. The output from the inverter to each condenser fan motor will pass through a motor starter which will protect the inverter in the event of a motor failure. The greater control of condenser head pressure will increase the efficiency of the Chiller and reduce the amount of energy consumption.
CONTROLS UPGRADE
The existing controls were replaced with new Carel PCO5 units, which represent the most advanced offering available in the field of programmable controllers. The system selected for this application included bespoke strategy, which was created to integrate existing BMS ‘Doorway’. These controllers and boards were installed into new customized electrical plates. In addition, new sensors and pressure transducers were fitted to each circuit of the Chiller and wired back to the control boards in addition to the replacement of all safety devices.
COMMISSIONING
Following the above works, each circuit was recovered into certified cylinders and pressure tested with oxygen-free dry nitrogen to 10bar. Any leaks identified were repaired. Each circuit was then progressively re-pressure tested with all valves open to 10bar. When stable and holding, the high side was isolated from the low side and the pressure in the high side increased to 24bar. A minimum 12hr drop test was carried out. Pressures were witnessed and signed off by the appointed client personnel before and after the test. Any failure of the drop test was resolved as appropriate and re-tested as above. Upon the acceptance of the drop test the nitrogen pressure was vented and the circuits evacuated down to 2torr, with a further 20-minute rise test. All data was logged and documented during the commissioning process and a copy of the operational report and Carel PCO5 controller’s configuration was given to the client
Scope of Works Carried Out:
- Recovered any remaining refrigerant from the Hitachi Chiller into certified cylinder.
- Weighed and confirmed the system charges.
- Replaced the fan motor.
- Checked operation of the EEV.
- Checked compressor operation and oil fault.
- Replaced the filters and new oil charge added.
- Charged the system with OFN (oxygen free nitrogen).
- Any leaks found were repaired by means of brazing over.
- Once proven the unit was leak tight released the oxygen free nitrogen.
- Evacuated the system to a minimum of 2 Torr.
- Re-charged the unit with virgin refrigerant.
- Test ran and re-commissioned.
- Completed all waste paperwork.
- Cleared site of any waste created.