This control scheme would be used in a typical medium sized commercial building which uses two port control valves on its chilled water system air handling plant. It has three air cooled chillers. The system switches on the chilled water system in the morning by means of an 'Optimizer controller' for the whole building. An optimizer takes over the functionality of a standard time switch. The energy optimizer uses an outside temperature sensor and a room temperature sensor to decide when the most energy efficient time is to switch on the plant in order to get the building up to the correct temperature in the rooms for the time the building users arrive into work. The chillers are sequenced from the return water temperature. The lead chiller selected is rotated on a weekly basis. When first switched on the control system will only enable one chiller. When there is enough demand for a second chiller the control system would open the isolation control valve on that chiller. When the isolation control valve is proved to be fully open by means of a limit switch the chilled water primary pump for that chiller would start. When the pump was running a flow switch would verify water flow and enable the chiller to run on its internal controls.
The system also has a secondary chilled water pump set. Each pump has its own variable speed drive. The lead pump is rotated on a weekly basis. The lead pump speed is then controlled by a differential pressure switch across the flow and return headers. There is a back up pressure relief control system should the variable speed drive be in manual.
We supply, design and commission the complete control system consisting of the chilled water plant motor control centre, all valves, actuators, linkage kits, temperature sensors and thermostats and full handover documentation with commissioning certificate for the above control scheme.
Swarpro Limited, 71-75 Shelton Street, London, WC2H 9JQ
Registered in England Company Number 0766703
VAT Registration Number 184 064 211