Clarkson Controls completes MOD contract

Clarkson Controls has completed the control system of the new purchasing office block of Defence Support Group Land Supply at MOD Donnington in Shropshire. The installation comprised BACnet control devices and products from several suppliers.

An Elesta RCO BACnet-enabled master controller controls natural-ventilation units on the roof, Sun tubes and the radiator heating systems and is located in the plant room control panel, which also offers control and monitoring to the district heating plant, pump sets and DHWS system.

There is a further RCO control panel for two central-core AHUs serving toilets and meeting rooms.

The displays of the two controllers can be used to view and change parameters in each controller — most useful in this instance as the AHU panel is in the secure area of the building, whilst the heating panel is in the less-secure externally entered plant room. Both controllers are connected via the IP network to a BMS central computer running Elesta BACnet software.

Each building zone has been fitted with Clarkson intelligent BACnet temperature and CO2₂ sensors. These MSTP-capable sensors are linked with a 2-core screened cable which in turn communicates with the Elesta master controller.

Information from the chosen items in the BACnet object list is passed to and from the sensor and acts with the RCO control algorithms to produce within the sensor a 0 to 10 V signal to operate the natural-ventilation units for each area.

A second input/output is used to open/close the Sun tube damper to darken an area for presentations etc.

The heating zone valves in the plant room are controlled via RCO output modules using temperature data from zone sensors.

Using BACnet/ MSTP communications and having 0 to 10 V outputs within the sensor minimises site wiring. By using one set of sensor values, energy-saving control interlocking within the software algorithms prevents heating and natural ventilation ‘crossover’ of set points to improve energy efficiency.

Internal frost protection and optimum start/compensation routine inputs are also afforded via the sensors.

External weather conditions are monitored by an Elsner weather station connected to one of the RCO controllers, which, in the event of adverse weather conditions, closes the natural-ventilation units or sets them to a minimum position depending on seasonal or CO2₂ need.

For more information on this story, click here: May 2011, 103
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