Compact 45 A03 Alarm

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The Compact 45 pellet boiler, like all the other models on the range, features both a water pressure switch and air pressure switch that provide a safety cutout function on the appliance, raising both an alarm (A03) and immediately shutting down the appliance and preventing the auger from turning to stop further fuel from being delivered to the grate. Both of the safety switches must be closed to created a circuit, to prevent the alarm being raised - they are both wired in series (see Compact 18 / 24 / 35 Circulator Kit installation manual for further details).


The water pressure switch will only close if the water pressure exceeds 0.4 - 0.5 bar; The air pressure switch will open if the Positive pressure in the flue exceeds 100Pa.


The Compact 45 also features a self cleaning grate. During the startup process, the grate will be rotated down into a vertical position to tip any ash and deposits into the ash pan. It will then rotate back into its normal horizontal position. The rotation of the grate is performed by a Belimo valve. There is a microswitch on the valve which will close only once the grate is in the fully home position. This switch is also wired in line with the water and sir pressure switches on this appliance. Therefore, if the grate is not fully in the home position, this issue can also raise an A03 alarm.


It has been reported on other appliances that feature the self-cleaning grate that it has seemingly not returned fully home to its normal horizontal position after tipping, and raised an alarm. The reason for this is likely due to the fact that the microswitch in the motor has not been correctly adjusted for this application. If incorrectly set, the microswitch will not close even if the grate is fully home.


The Belimo is positioned below the rear of the boiler and combustion chamber assembly and can be seen by removing the right hand side outer panel of the boiler, as below:



Location of Belimo valve in Compact 45


The following image shows the correct position for the dial that controls the adjustment of the microswitch. Note that this is the upper of the two switches, and it should be pointing in the 5 'o clock position:



Compact 45 Belimo valve correct calibration


If the dial is not pointing to the position shown, it should be carefully adjusted as required.


Note also the correct position of the U-Clamp that holds the motor to the spindle of the grate. This should be hard against the stop indicated when the grate is in the 'home' or closed position.

On No account should the lower of the two dials be adjusted as the correct operation of the grate may otherwise be impaired.