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MACH® Series
Gas-Fired Boiler Maintenance
Page 35
5.5.2 Auto-reset Service Codes
Code Lockout Description
b 08 Air pressure switch open. The air pressure switch failed to close to indicate sufficient air flow to start the boiler.
b 18 Outlet high limit temp. The outlet water temperature has exceeded the internal high limit temperature setting.
b 19 Return high limit temp. The return water temperature has exceeded the internal high limit temperature setting.
b 24 Switched inlet / outlet. The inlet water temperature has been more than 18° F above the outlet for more than
75 seconds.
b 25 Outlet temp rapid change. The outlet water temperature is increasing too fast. Indicating low flow condition.
b 26 High exhaust back pressure. The high exhaust back pressure switch is tripped indicating a blocked stack, inlet, or
condensate system.
b 30 Max delta T. The temperature rise across the heat exchanger is greater than maximum allowed,
indicating insufficient flow.
b 40 Flue sensor open. The flue gas temperature sensor is indicating an open circuit.
b 52 High flue temp. The flue temperature has exceeded the maximum allowable setting.
b 61 Air pressure switch closed. The air pressure switch failed to open prior to starting the blower.
b 65 Fan speed incorrect. The fan is being directed to a higher speed than it is achieving.
WARNING
If any “Manual Reset” limit device trips,
DO NOT
reset without determining and correcting the cause.