Hamworthy Gas Pressure Switch 5-40 Mbar Range 533925004

The Hamworthy 533925004 is a gas pressure switch with a working range of 5 to 40 mbar. It monitors gas pressure on the appliance and signals the control circuit when the pressure sensed at the tapping falls outside the set threshold, proving that gas is present at the required level before the burner sequence continues. It is used across Hamworthy floor standing commercial and domestic appliance families, including ModuMax and Purwell Variheat models.

• The appliance locks out or fails to complete its ignition sequence despite gas being available at the meter.
• Repeated lockouts that clear on reset and then return shortly after.
• Intermittent shutdown during a call for heat, with the burner dropping out without a demand change.
• No proving signal from the switch, so the control board never permits the gas valve to open.
• Erratic or drifting switching points, where the appliance behaves differently on each start attempt.

• Match your appliance model against the compatibility list, as the same switch body is used across several ModuMax and Purwell Variheat variants.
• Confirm the part number on the existing switch or in the appliance manual before ordering.
• Note the alternative number 2062150, which may appear on older listings or labels for the same item.
• Check the condition of the sensing pipework and connections when the switch is replaced, as a blocked or weeping tapping will affect the pressure reading.