Taking care of historic buildings
A challenge for all building services industries working with historic buildings is to bring them technically up-to-date while protecting the fabric and the building’s visual impact. In protecting the building it is important to keep drilling and other invasive fixings to a minimum, while visually new plant and equipment must be discreetly installed in order to preserve its architectural history. This was the challenge when PA Collacott & Company was awarded the building controls contract for Charterhouse covering the refurbishment of the existing building management system (BMS), which also included a new language block.
Charterhouse is one of the great historic schools of England and dates back to 1611 when a Carthusian monastery, established in the 14th century, was converted to a hospital for pensioners and a school for boys. In 1872 the school moved to Godalming and on a 200-acre estate educates both boys and girls, each with their own residences.
The refurbishment included halls, teaching blocks, dining rooms, sports hall, theatre, chapel, and halls of residence. In addition, a new language block was erected. The existing BMS was upgraded with controllers from Priva Building Intelligence which needed to address three main requirements: backward compatibility, integration with other manufacturers’ systems, as well as provide a platform for future-proof building control.
“When refurbishing or extending a building, the challenge for the BMS is to bring together a host of building services plus their diverse range of communications systems,” stated Anders Norén, Managing Director of Priva Building Intelligence Ltd. “And the diversity can be great, dependent of the size and sophistication of the building services. BACnet over RS485 or IP is supported by most HVAC control systems. Metering, chillers and inverters commonly utilise Modbus in the UK, while M-bus is also used in the metering of utilities. Two of the protocols employed in lighting are EIB/KNX and DALI. In the management and interpretation of data, XML is used for the exchange of data between web based applications and devices; LonWorks typically serves HVAC, lighting and process devices on a network; OPC server and OPC client enables PC to PC applications; and TCP/IP is used to transmit data across communications networks, such as an organisation’s IT network or the Internet.
“Generally the number of buildings utilising all of these protocols is in the minority, but nevertheless, when specifying a new BMS or selecting additional controllers, it is important that they offer optimum interoperability in order to integrate with existing plant and equipment and provide a valid solution for the future.”
The Priva controllers installed were a direct replacement for the older BMS, providing monitoring and control of the school’s heating, cooling and ventilation systems, plus energy savings through its optimum start and weather compensation programs. While within the new language block the Priva system is managing a natural ventilation system and underfloor heating.
A major consideration for the school was the retention of existing sensors and cabling within the new BMS. As Geoff Collacott, Director of PA Collacott & Company explained: “Even though the previous BMS and its peripheral equipment was supplied by a different manufacturer, we were able to utilise the sensors and cabling because Priva controllers support any temperature sensor, do not require screened cabling and are equipped to communicate with a range of protocols. This has led to savings in capital cost and installation time.” With some 150 existing sensors, miles of cabling running throughout the site and the time required to install both, Geoff estimates that the project cost was cut by 15%.
“All too often usable equipment is removed from buildings during a refurbishment and, as we have shown at Charterhouse, it isn’t always necessary. Historic buildings in particular reap the benefits of retaining usable installed equipment as their retention means no new drilling or fixing is required; a very important factor in the preservation of its fabric and the maintenance of its visual appearance.”
In addition, an impressive cost saving has also been made by the installation of a reliable BMS. In the past, considerable costs were incurred in the repair and maintenance of the previous BMS which can now be redirected onto worthwhile projects.
Since its completion, P A Collacott & Company has been back to site to improve the management reporting capabilities of the BMS. Priva TC Vision has been installed allowing the sports hall manager to review and make changes to the building. “However, we programmed the new software to be ‘blind’ to all other buildings on the site, putting only the sports hall under his control,” said Geoff. At the same time Priva TC Web Vision was installed, allowing system interrogation by a greater number of people.
TC Vision is a PC application for local and remote control with graphics, event and data logging, energy and runtime tables, documentation and alarm overviews. TC Web Vision is a webserver application for web based access with every visualisation option to control all Priva systems remotely using the intranet or the internet.
The school continues to upgrade elderly plant with the latest high efficiency boiler and pump systems that are easily interfaced with the new BMS. Being of modular construction, additional input and output cards can be easily added to accommodate any new plant control or monitoring points. By using the Priva TC Select programming tool to engineer the outstations, the head-end graphics are immediately updated without disruption to the whole system.
Automated control and monitoring of the many and varied boiler and air handling installations by the BMS allow site engineers to concentrate on the planned maintenance of plant whilst insuring the correct protection to the fabric of the many historic and modern buildings.
Environmental responsibility is uppermost in the mind of the school with closer monitoring of gas, electricity and water usage. Opportunities for further energy savings will come from this enhanced monitoring, together with performance optimisation of plant and equipment. Monitoring of existing and new plant will enable ‘real time’ maintenance in place of calendar based maintenance, providing the site with a more efficient and cost effective regime. Any deterioration of plant failures will be reported and resolved without undue disturbance to the buildings’ occupants.
“Whilst good policies are already in practice, it is important that we continue to support and develop any new energy saving schemes with the school,” said Geoff. “For example, there is the possibility of connecting to a DALI lighting interface which has been applied to one of the buildings.” DALI is a digital addressable lighting interface protocol that offers opportunities in lighting flexibility and energy savings; mainly from the ability to dim lighting from 100% to 1%, but also from its ‘soft start’ capability that maximises the service life of a lamp.
“The skill to good control is to ensure that the system being installed has the capability of backward compatibility, interoperability and future-proof expansion,” concluded Geoff.