Oxford’s popular ice rink has benefitted from a major improvement programme that includes a custom-built natural refrigerant cooling system installed by J & E Hall which is delivering increased energy efficiencies, cost savings and addresses environmental concerns.
Oxford’s ice rink is very well used and was starting to show its age in the fabric of the building as well as the plant room. Towards the end of last year the council therefore approved a £700,000 improvement programme which included replacing its aged refrigeration system and refurbishing the complex.
The phase out of virgin HCFC’s in 2010, concerns over the availability of recycled R22 refrigerant coupled with rising service and maintenance costs for a chiller that had reached the end of its lifespan necessitated a replacement, but the Council was keen to ensure that any new system met its environmental requirements.
J & E Hall’s South East Division secured the contract to supply a bespoke 360kW Ammonia Chiller featuring two HallScrew compressors for built in redundancy and designed in accordance with BS EN 378:2008
Ammonia was specified as it offers an organic and natural refrigerant with an ODP (Ozone Depletion Potential) of zero, negligible GWP (Global Warming Potential) and offers better efficiencies than blended refrigerant gases. Ammonia’s superior thermodynamic qualities also mean less electricity is used and its recognisable odour is a safety asset as any leaks are unlikely to escape detection.
The plant design incorporated variable frequency drives for capacity control to enhance the performance of the chiller at part load, which can reduce running cost by up to 20% with a pay back on its cost of less than 18 months.
As the Council had a number of stakeholders to consider and potential losses of revenue, J & E Hall had to complete the work within a three-week time frame.
When the ice was removed J & E Hall carried out a rigorous inspection to ensure there were no leaks in existing headers, service ducts etc. All the pipe work from the brine pumps to the new chiller was replaced and the chiller was supplied on a skid and located externally but adjacent to the existing R22 plant room on a concrete base with a custom-built louvred housing that ensured it maintained the specified low noise levels required.
The chiller cools 178m3/h of calcium chloride indirectly via heat exchangers from an incoming temperature of -8ºC to -10ºC leaving and provides cooling with
two compressors operating at 360 kW using R717 refrigerant (Ammonia).
Two Fridgewatch 4000 controllers were fitted to the chiller package and electrical panels were installed in an existing plant room. The air cooled condenser used energy efficient variable speed fans and formed part of the packaged built chiller which also incorporated the two compressor packs and flooded evaporator.
The Fridgewatch microprocessor controllers which feature touch screen displays provide the starting logic for the compressors and a control loop allows the compressors to be automatically controlled locally.
A central SCADA (Supervisory Control And Data Acquisition) system provides greater control and flexibility to monitor the chiller in real time remotely via broadband and enables the settings to be adjusted if required, via Internet Explorer.
J & E Hall featured heat recovery in its design and the heat generated has been used to supply domestic hot water with a new boiler bringing it up to the required 70/75ºC. Waste heat is also being used to supply the heated pad which prevents the ground underneath the ice rink from freezing.
Oxford’s rink has 80 cubic metres of ice with a thickness of four centimetres. To ensure it kept to the three week time scale J & E Hall brought in temporary chillers to speed up the ice making process which can take up to 10-days.
The rink was re-opened on time and within budget. J & E Hall ensured that the new system has been robustly designed and supported with a comprehensive service and maintenance programme via its network of 120 engineers to maximise the rink’s operational longevity. The compressors have been designed for continuous operation for a minimum period of six years or 25,000 running hours (six years) before requiring any inspection.
Bob Timbs, city council executive member responsible for leisure, says “The ice rink is a much loved facility. The new chiller has enabled us to keep the existing rink operating for many more years.”