High efficiency boilers and chillers and other plant; 60% to 70% heat recovery on air plant; a façade combination of high performance double glazed units and triple skin external ventilation; and automatic solar blinds will all contribute to optimum energy usage and a consequent emissions rating designed to exceed Part L by more than 20%.
Installing the systems to control the plant and so help to achieve the energy objectives has been in the hands of Wokingham systems house Integrated Controls Systems who won a £650,000 contract awarded by Bovis Lend Lease.
An intelligent system
The structure and specification of the highly intelligent system called for extensive localised control of variable speed drives, eliminating the requirement for centralised motor control panels. To achieve the objectives, ICS interfaced with plant power centres, the large LV distribution boards provided by electrical contractors who undertook power wiring to the variable speed drives or other packaged pieces of equipment.
ICS carried out all secondary wiring from the VSDs to the various devices they served and interfaced them with the building management system.
ICS in fact took the role of lead co-ordinators between electrical contractors and the mechanical contractors who supplied additional pieces of equipment to the project.
In the absence of traditional panels, ICS built 25 distributed BMS plant controls enclosures dedicated to specific pieces of equipment or plant, normally determined by their location in the building.
The enclosures variously control boilers, pumps, chilled water plant and air handling units and monitor passenger lifts, smoke extract systems, public health amenities, landlord and tenant switchboards etc.
To cater for a possible dual tenancy of the building, two enclosures on each of the seven floors have been fitted with a Cat 5 interface offering the facility to connect Tridium JACE (Java Application Control Engine) communications controllers/routers to constant volume boxes and the 64 fan coils on each floor.
Management platform
In essence, the JACE has been used as the management level platform using a LON interface to connect to the constant volume boxes and fan coil units; a separate ModBus connection to a series of electricity and all other metering operations; and BACNet communications with the variable speed drives.
ICS Managing Director John Reid says: “The initial specification at Bow Bells was for an infrastructure to meet all of the HVAC requirements. We have provided added value by enabling landlords and tenants to connect their own metering systems into our infrastructure rather than using additional dedicated systems.”
Further added value at Bow Bells came through the ability of the ICS installation to support the automatic blind system, siting the Somfy controls package on the same pc as the BMS and wiring in the motor controllers connected to the blinds and associated control sensors.
Lighting systems, according to John Reid, could be similarly treated through the fast growing Dali lighting protocol.
Making it easy
He points out that the distributed nature of the BMS controls facility not only minimised wiring, by placing controllers discretely around the building adjacent to the equipment they serve; it also did away with some of the traditional features of a standard motor control panel by using a BACNet link to monitor operating parameters, status etc. This has enabled standard operations such as the operation of variable speed drives in hand to be carried out via an integrated key pad rather than interrogating a control panel with switches displaying alarms and other status information.
“There is a seamless link; the variable speed drives are now an extension of the BMS,” he says. “They are effectively another controller node and should be used as such. They are programmable and in certain circumstances associated BMS devices such as dampers and actuators have been directly connected to the VSD.”
An open system
ICS expertise combined with Tridium’s flexible communications capability has created an installation that not only controls central plant systems by the use of various communication mediums, but also features an infrastructure that is able to support many additional activities over and above the initial HVAC requirements.
“”This open system has power and versatility that offers tremendous opportunities for owners who commit to Tridium. The system is so flexible and comprehensive we can satisfy almost any communications application,” adds John Reid.
Having completed the shell and core contract for Bovis Lend Lease and Roger Preston and Partners, the consultants, ICS are currently undertaking the fit out of three of the floors at Bow Bells for Icelandic bank Landsbanki.