Case Study: Mercury Chiller Upgrade
Client: Communications Organisation
Location: Heathrow, Middlesex
Solitair Services Limited was commissioned to provide a specialist sub-contract service, to carry out a project involving the partial re-engineering of a Mercury Air Cooled Chiller. The chiller had in the past suffered from numerous losses of refrigerant charge and the failure of several compressors.
Due to the plant being located within the basement of the building (posing logistical implications if replacing the existing chiller), it was decided that the re-engineering of the existing chiller was the most economical proposal.
The existing eight scroll compressors were removed and replaced with two Hanbell screw compressors. All necessary pipe work modifications were carried out, along with the installation of electronic expansion valves.
The Mercury factory fitted basic controller was removed and replaced with a Trend IQ 4 Intelligent Controller. The installation of the Trend Controller has resulted in improved chiller control, better set-point adjustment and temperature/pressure monitoring of the refrigerant circuits. A variable frequency drive unit was also fitted to allow infinite control of the condenser fans. The VFD was programmed to utilise a function within its control strategy. This function has the ability to limit the head pressure control, by unloading the screw compressors. Consequently this will result in reduced load of the chiller, but ultimately ensure continued compressor operation during periods of high ambient conditions.
Data logging equipment was also used to monitor the chiller operation, which proved to be an invaluable visual tool, allowing the chillers improved efficiency to be clearly demonstrated to the client.
