6 MM Features
Mk8 MM Manual Page | 135
6.10 Purge Pressure Proving/ Purge Hold
Setting option/ parameter 155 to 2 makes terminal 81 a purge pressure proving input. In this case a pressure
switch to provide the purge pressure proving signal needs to be installed and the feedback connected to
terminal 81. The switch must be made continuously for the whole duration of the purge time. If the signal is
lost the purge time stops and it restart when the switch is made again. If the switch is made before the
blower motor starts a lockout is generated.
Option/ parameter 158 allows to set a timeout for the purge pressure proving. If the system does not see a
signal on terminals 81 within the time set in option parameter 158 a lockout is generated. Setting option/
parameter to 0 disables the timeout functionality and the MM will stay in the purge phase indefinitely.
To allow for a quick cool down of the boiler a manual switch can be added to the panel. This switch can then
be used to break the feedback from the pressure switch to the MM causing the MM to stay purging for the
desired time period.
Caution: When it is desired to end the continuous purge, it is necessary to disable the burner prior to turning
the manual switch back to the normal position. Otherwise the burner will start up.
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