7 Intelligent Boiler Sequencing - IBS
Mk8 MM Manual Page | 145
As well the options/parameters given in section 5.3.1, the following also need to be set for steam
sequencing:
• Option 41 – Sets whether all the lag boiler states, either the first lag is kept in standby state with the
second lag in warming and the remaining lag MMs off, or all the lag boilers after the first lag boiler
are kept in warming state and there are no boilers offline.
• Option 42 – Sets the standby setpoint for sequencing where non-return valves are installed; the first
lag boiler will aim to maintain this standby setpoint when in the warming/standby phase. This is set
as absolute value.
• Options 53 – Sets the steam sequencing burner off time. This is the time in minutes for how long the
boiler will be off for during Warming mode.
• Option 54 – Sets the steam sequencing burner on time. This is the time in minutes for how long the
boiler will be in low flame hold for the boiler to heat up to its standby setpoint, when in Warming
mode. Option 42 sets the standby setpoint.
7.4.3 Low Pressure Steam Sequencing
For steam boiler plants where check (non-return) valves are not installed, or the required setpoint is less
than 2 Bar (20 PSI), it is not possible to use a standby setpoint. Each pressure sensor would read the same
pressure value, regardless of individual boiler temperature/ pressure. A thermostat (Aquastat) can be
installed into the boiler shell, and option 40 must be set to low pressure steam sequencing.
For the Mk8 MM, a 230V/ 120V input on terminal 93 (see option 79) will initiate the warming for that lag
boiler, and this will fire according to the warming interval timings in options 53 and 54.
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