Sequence Of Operation (Example: Four-Modulex Boiler Installation) - Watts AERCO EXT Installation, Operation & Maintenance Manual

Ufly Controller and BCM for Modulex EXT
CHAPTER 6: BOILER COMMUNICATIONS MODULE (BCM)

6.9.1 Sequence of Operation (Example: Four-Modulex boiler installation)

When there is a need for heat, ACS will send a fire rate signal to the first boiler to begin firing.
The Boiler Communications Module (BCM) of the first boiler will turn on one of its modules. When
the ACS fire rate signal to this boiler reaches a value twice that of the start level percentage
(programmed by the user into the ACS), the ACS will call on the second boiler to begin firing one
module, and the ACS will then split the fire rate signal between the two boilers and send each a
signal equal to the start level percentage. When the combined ACS fire rate signal to the two
boilers reaches a value three times that of the start level percentage, the ACS will call on the third
boiler to begin firing one module, and the ACS will then split the fire rate signal between the three
boilers and send each a signal equal to the start level percentage. As the demand increases, in
a similar method as above, the ACS will call on the BCM of the fourth boiler to turn on one
module. At this point, the ACS will modulate the fire rate signal to the boilers in a parallel manner,
while the BCM of each boiler sequences the individual modules.
Boiler inputs will modulate down and come off line in response to the ACS in a reverse manner.
Whether the ACS is set in a Constant Temperature or Outdoor Reset mode, it will use the
modulating ability to prevent header temperature fluctuation and maximize efficiency. As well, the
ACS can stage auxiliary equipment such as combustion air dampers and fans. Refer to ACS
Manual GF-131, and Product Spec ACS for details.
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