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Priority Domestic Hot Water (PDHW)

This method of controlling the hot water and heating allows the hot water cylinder to take priority over the heating circuit when there is a demand from the cylinder sensor, this allows the water to be heated to a higher flow temperature in relation to the central heating water.

Combination boilers use this method, when the hot tap is opened, the flow switch senses movement and moves the diverter valve over to allow the boiler to heat the mains water instantaneously producing hot water out of your taps taking priority over the heating circuit, when the tap is closed the boiler reverts back to heating mode and reduces the boiler water temperature to the set level on the control panel of the boiler.

The advantage of a PDHW set up allows the system to be run a 2 different flow temperatures. The hot water cylinder can be reheated at a considerably quicker timeframe using a high flow temperature and operates at the boilers maximum kW output with all the energy being used to heat the coil in the cylinder. Once the hot water is satisfied the boiler then reduces its flow temperature and kW output to suit the central heating, allowing the circuit to operate at its designed heating output. This is controlled by the use of either 2 port valves or a 3 port valve depending on the set up and control option used.



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