Worcester Bosch Flow Switch Assembly 87161020390

The Worcester Bosch 87161020390 is a flow switch assembly specified for the Heatslave 26/32 range of oil-fired combination boilers. It sits in the domestic hot water circuit and responds to water movement when a hot tap is opened, sending the signal that brings the burner on for a DHW demand. Worcester Bosch lists this assembly against the Heatslave 26/32 combi and its OSO and RSO variants, so it is the correct pattern for that appliance family rather than a generic switch.

• No hot water, or hot water that only arrives intermittently when a tap is opened
• The boiler does not fire on a domestic hot water demand, even though the heating side runs normally
• Burner short-cycling or dropping out part-way through a draw-off
• A lockout or fault indication linked to the flow switch or the DHW circuit
• Scale, sludge or debris found around the switch body or its connections on inspection

• Confirm the appliance model and serial number against the compatibility list before ordering, as the assembly is listed for the Heatslave 26/32 family only.
• Check the markings on the old switch; the alternative numbers 1013779 and N7171 may be stamped on the component you are replacing.
• Inspect the housing and any seals when the old switch is removed and renew them if they show signs of damage or hardening.
• This part is fitted to a gas appliance; installation must be carried out by a Gas Safe registered engineer.