Multiple boiler control system and method of operation

A method for operating a boiler system for a medium to be heated, said system including a plurality of boilers each capable of being regulated in modulation level as a proportion of its fully turned-on condition, said method comprising the steps of:

• generating a DUTYCHANGE signal representing the amount of energy required to change the temperature or pressure of said medium from its actual temperature or pressure to a desired temperature within a predetermined time;
• selecting one of said boilers as the lead boiler;
• regulating the modulation levels of the boilers in a predefined sequence starting with the lead boiler when DUTYCHANGE has a positive value;
• defining for each boiler a FIRING point corresponding to the minimum modulation maintained by the boiler when it is turned on and MOD point corresponding to a modulation level of said boiler at which a subsequent boiler is enabled to be turned on;
• inhibiting a boiler from being brought below its FIRING point until the preceding boiler is brought below its MOD point.

A control system for a boiler system for a medium to be heated, the heating system being of the type including a plurality of boilers operated in a predefined sequence, each boiler capable of being regulated in modulation level as a proportion of its fully turned-on condition, said control system comprising:

• means for generating a DUTYCHANGE signal representing the amount of energy required to change the temperature in said medium from its actual value to a desired value within a predetermined time;
• means for selecting one of said boilers as the lead boiler, with which said predefined sequence is started when DUTYCHANGE has a positive value, the boilers being operated in the reverse sequence when DUTYCHANGE has a negative value;
• means for defining for each boiler a FIRING point corresponding to the minimum modulation maintained by the boiler when it is turned on and a MOD point corresponding to a modulation level of said boiler at which a subsequent boiler is enabled to be turned on;
• and
• means for inhibiting a boiler from being brought below its FIRING point until the preceding boiler is brought below its MOD point.