Hamworthy AA072173 Air Pressure Switch S2 70-120

The Hamworthy AA072173 is an air pressure switch rated S2 70-120, fitted to Hamworthy appliances. It monitors the pressure produced by the fan or flue system and confirms that air flow is present before the appliance is allowed to fire. If the required pressure is not sensed, the switch keeps the burner off and the appliance locks out.

• The appliance locks out shortly after the fan starts, with no ignition.
• The fan runs but the burner never fires, and the fault repeats on every demand.
• Intermittent lockouts that clear on reset and return later.
• A fault code or status indication relating to air pressure or air flow proving.
• The switch does not change state when the fan is running, or the sensing tube holds no pressure.

• Confirm the appliance model and check the part number against the manufacturer's parts list.
• Read the rating and designation markings on the existing switch and match them to S2 70-120.
• Inspect the sensing tubes and pressure connections for blockage, splits or loose fit before assuming the switch has failed.
• Check the electrical connections and terminal arrangement on the existing switch against the replacement.