Potterton DHW Diaphragm Flow Switch 10/18676

The Potterton 10/18676 is a diaphragm flow switch used on the domestic hot water circuit of Potterton gas boilers. It detects water flow through the DHW side of the appliance and signals the boiler to fire for hot water demand. It is listed under boiler switches and supersedes the earlier code 451100.

• No hot water demand registered — the boiler does not fire when a hot tap is opened.
• Hot water runs cold or intermittently while the central heating continues to work normally.
• The diaphragm is split, perished or stiff, so it no longer moves the switch actuator.
• The switch contacts fail to make or break cleanly, causing erratic firing on DHW.
• Water weeping or staining around the flow switch housing.

• Confirm the boiler model and, where applicable, the control type fitted (SIT or Honeywell) against the manufacturer's parts list.
• Check the part number on the existing switch or its housing matches 10/18676.
• Inspect the diaphragm and switch assembly for mechanical damage before condemning the part.
• Isolate the water and power supplies before removal and refitting.