Two-port (variable flow) control strategy
Heat Interface Units (BG 62/2015) was written by Reginald Brown and published by BSRIA in December 2015. It states: ‘In two-port control, a two-port control valve varies the flow of water through the heat emitter in order to vary the heat output. A typical example of a two-port control valve is the thermostatic radiator valve. In order to achieve good control, the pressure differential across the valve should be relatively constant. This is achieved by utilising a variable speed circulation pump with pressure control. If a constant speed pump is used then the pressure differential increases as the valve closes, resulting in poorer control and waste of pump energy. The benefit of two-port control for the heat emitters associated with heat networks is that it minimises the return temperature.’
--BSRIA
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