BMS ModBus capability gives major savings for Swindon college buildings

The ModBus capability of the Priva building-management system in new college buildings at Swindon has reduced installation and hard-wiring costs by about £6000.
The use of the ModBus communications protocol and the IT network at an education centre in Swindon is estimated to have saved about £6000 on installation and hard-wiring costs of a building-management system from Priva Controls. The North Star Campus consolidates two major adult-education centres onto one site. The new buildings comprise a teaching block, performing-arts facility and teaching workshops. The buildings are heated and cooled using standard variable-temperature systems, air-handling units and comfort cooling via a Mitsubishi Electric VRF system. Managing the HVAC services, as well as monitoring the electrical load, controlling the automated windows and enabling lighting is a Priva building-management system installed by Bailey Energy & Controls. There are about 250 points, managed by three Compri HX8 controllers serving the teaching block and the two workshops and a Compri HX4 for the kitchen area. One of the main tasks of the BMS is managing the mains electricity and sub-meters. Andy Vidler, application engineer with Bailey Energy & Controls, explains, ‘Part L2 of the Building Regulations states that new buildings must be capable of monitoring 90% of the energy load. As a result, over 50 meters, both main and sub-metering, have been installed. The meters have been supply by Northern Design with ModBus communications, with which the Priva BMS is fully compatible.’ By recommending a Priva system, Bailey reduced the budgeted BMS cost by about 5%. Andy Vidler says, ‘Specifying Priva was not based purely on cost but on the openness of the controllers. Due to its open protocol design, we had no hesitation in recommending that the BMS should sit on the building’s IT network — a solution welcomed by the college once network integrity has been demonstrated. ‘Being a new build, it proved quicker and simpler to install a Priva network, providing immediate communications with the intelligent outstations as they came online, and then connect this network to the Ethernet. Communication between the BMS and the Mitsubishi VRF system proved equally seamless due, once again, to Priva’s open-protocol approach.’ Other energy-saving systems include automatic control of the library windows and lights. The double-height library has automatic control on its four large windows. Vertically placed sensors monitor the room temperature; as it rises, the windows are opened sequentially. There is a rain sensor outside. The BMS enables the lights early in the morning for the cleaners and again when staff and students arrive. The analytical power of the Priva BMS is being used to monitor a range of equipment, including the efficiency of the hot-water calorifiers, mains electricity, sub-meters and the VRF air-conditioning system. The 21 indoor cassettes on the VRF system are individually monitored. Bailey has produced a graphic interface showing setpoint (which can be adjusted at the keyboard), return-air temperature, whether a unit is heating or cooling and on/off state. Information from all 50-plus meters can be obtained in text and graphical form for intervals of 15 minutes, day, week, month, quarter, year and overall total. Support for Bailey during the project included comprehensive training at Priva’s headquarters in Holland.
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