Programming of the works was of major importance - the central Plant Room provides the primary LPHW heating, domestic hot and cold-water services to the entire College which remained in use throughout the construction period. In this respect an enabling works contract was introduced to minimise the impact of the main refurbishment works. The enabling works included the removal of asbestos insulation, alterations to the existing chimney flues (to ensure compatibility with modern gas fired condensing boilers), replacement of the ventilation systems providing combustion air to the boiler plant, provision of a standalone temporary plant room, associated builderswork, etc.

The main refurbishment works were completed over a highly concentrated fourteen week working programme; and with much careful planning, including the offsite pre-fabrication of large sections of pipework and ancillary components the project was essentially completed on time and within budget.

Extent of Mechanical Services:

• 3 No. Potterton NXR3/9 gas fired, condensing boilers with fully modulating pressure jet burners and a combined heat output rating of 870kW.
• Owing to the relatively high LPHW system content, in excess of 10,500ltrs, a “pressure-less volumetric expansion system” was incorporated. The volumetric expansion is controlled via an open vented cylinder containing a butyl membrane; on system heat up a bypass opens to allow direct expansion into the cylinder with excess pressure reduced by flexing of the butyl membrane. As the system cools, line-pumps transfer the water from the cylinder back into the primary circuits.
• The plant room contains a total of 8No. individually pumped circuits, with pump duties ranging from 0.5 kg/sec @ 25kPa to 12 kg/sec @ 100kPa.
• The domestic cold-water services (and HWS cold feed) are fed from a pre-insulated GRP break tank, with a nominal storage capacity of 12,000ltrs. A cold-water pressure booster set complete with 3 No. variable speed pumps capable of providing a maximum simultaneous water flow rate of 6.5ltr/sec @ 3.0 bar gauge.
• Domestic hot water is provided via 3No. unvented “A O Smith IT300 indirect HWS calorifiers, each with a storage capacity of 300ltrs.
• A comprehensive Building Energy Management System, incorporating head-end supervisor and full graphics package, is provided to ensure the safe and efficient operation of all equipment. Increased energy efficiency of the plant has resulted in an average fuel saving of 35% per annum