Compact A02 Alarm - Technical parameters issue: CHECK DURING COMMISSIONING

Any Compact boiler supplied during 2013 and early 2014 should be checked during commissioning to ensure that certain technical parameters are correctly set. Any boilers supplied with software Versions 7 to 9 may have a parameter that determines the smoke temperature that the boiler considers it is switched off incorrectly set.

To check and correct this parameter, proceed as follows:

• From Settings Menu, select Technical Menu
• Enter relevent password
• Select Parameters option
• Scroll through to Parameter 11 (T Boiler On): Ths should be set to 45 degrees
• Scroll through to Parameter 18 (T Boiler off): This may be set to 60 degrees which is INCORRECT. This paramter must be adjusted to 42 degrees - select the parameter then using +- keys reduce value to 42 and save.
• Exit menu

Background

MCZ changed the parameter of the Compact range at which the boiler considers it is switched off at Software V.7 release. The value relates to the observed smoke temperature at the flue fan housing, after it has exited the boiler heat exchanger. Previously, the value was 42 degrees but this was raised to 60 degrees. The intention was that this higher 'off' temperature would ensure that the boiler switched off more rapidly after a shutdown/cooldown phase, and also come back up to temperature more quickly after ignition. However the result of this was increased intstances of A02 combustion failure alarms. This usually occurs when the boiler commences reignition shortly after having shutdown (within 5-10 minutes). Because the boiler is still relatively warm under these conditions, the boiler is already above the boiler 'on' temperature and although there is a 'hot start' logic in the software, ignition is not allowed to continue for long enough for combustion to establish (maximum of 2 mins - possibly only about 5 seconds): The boiler considers it is already alight and attempts to modulate into normal full power. Pellet delivery and fan speed goes to maximum, the brazier is swamped and no combustion establishes; the boiler then throws up a combustion failure alarm once the flue gas temp fall below 42 degrees.

Software version 8-9 should have an ammendment which reverts Parameter 18 (T Boiler off) to 42 degrees, but if it has not, the parameter shold be altered as descrived above.

From Software V.10, released February 2014, the 'Hot Restart' logic in the boilers was modified to overcome this issue.

Now, if when ignition phase commences the observed smoke temp is over the value of T Stove On (45 degrees), the observed temperature is recorded, then the igniter remains on (fan/pellet values also remaining at 'Load Wood' settings) until the observed smoke temp reaches 5 degrees above the recorded value at the start of ignition. At this point, the boiler concludes ignition is complete, the stove is alight and modulates to full power/normal running.