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Automatic bypass valves such as the Honeywell DU145 have been endorsed by the heating industry as the only acceptable means to regulate water flow through the boiler bypass circuit.
A gate valve or other fixed orifice opening is no longer acceptable, even when a flow gauge is used to set a minimum flow rate, because it reduces boiler energy by allowing excessive or unknown flow through the bypass.
Whereas an automatic bypass allows flow only when necessary and then by only as much as is required, industry tests show that a fixed orifice bypass allows heat wastage through the bypass even at times of maximum heat demand from radiators.The Honeywell DU145 automatic bypass valve has a unique and simple adjustment mechanism that prevents flow through the bypass while system valves are open,and increases water flow automatically as valves close – so raising energy efficiency by minimising bypass flow whilst providing a safe flow path around the boiler as specified in Good Practice 302.
