Case studies

Roche products - district cooling

Planning / Implementation / Main components

Star Refrigeration Ltd.


ammonia (NH3) / chilled water (H2O)

System start-up


Roche Products Ltd. is a major research-based healthcare company. Its site at Welwyn Garden City fulfils a variety of functions; including manufacture, R&D and administration. Part of the company's environmental policy has been to eliminate the use of CFCs.


The refrigeration requirements for individual buildings are dependent on the use that the building is being put to. Consequently, the site has a diverse and fluctuating cooling requirement. Therefore the new refrigeration plant should be flexible, with a capacity to meet the existing site cooling load and accommodate an envisaged short-term increase in demand as well as an easy upgrading due to further site expansion.


It was decided that Roche's present and future cooling demands would best be met by adopting the philosophy of a centralised water chilling plant using ammonia as the refrigerant.


Technical data:


Type of facility

3 screw compressor packages



Refrigerant volume

238 kg per chiller unit


chilled water

Refrigerant volume

hundreds of cubic metres

No. of refrigeration compressors


Refrigerant temperature

chilled water at +4.5 °C, condensing at +37 °C, water on to the condenser at +29 °C

Refrigerating capacity

approx. 2,500 kW per chiller unit

Main components

low pressure receiver, semi-welded plate heat exchanger evaporator, semi-welded plate heat exchanger condenser, evaporator chilled water circulating pump, condenser water circulating pump, packaged unit starter / control panel

Special features / Comments

condensing temperature floats with ambient temperatures to maximise plant efficiency; overall control by a Landis & Gyr BMS system, that looks at the cooling demands and signals individual chillers to operate; automatic oil change and air removal


Star Refrigeration Ltd.
Andy Pearson
Thornliebank Industrial Estate
Glasgow G46 8JW
United Kingdom
Phone: +44 (0)141 638 7916
Fax: +44 (0)141 638 8111
E-mail: This email address is being protected from spambots. You need JavaScript enabled to view it.