AERCO Modulex E8 Controls Guide - Manual (Page 75)

PR1: 11/30/12 Page 75 of 112
GF-115-C Modulex E8 Controller and BCM
Operations and Maintenance Manual
OMM-0084_0D
AERCO International, Inc. • 100 Oritani Dr. • Blauvelt, NY 10913 • Ph: 800-526- 0288
outside the BMS II/ACS, but boilers that fire with no flow will trip out on internal high
temperature limit controls.
The following example briefly explains the operational sequence for a boiler plant consisting of
multiple Modulex Boilers controlled by a BMS II or ACS:
7.8.1 Sequence of Operation (Example: Four-Modulex boiler installation)
When there is a need for heat, the BMS II 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 BMS II/ACS fire rate signal to this boiler reaches a value twice that of the
start level percentage (programmed by the user into the BMS II/ACS), the BMS II/ACS will call
on the second boiler to begin firing one module, and the BMS II/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 BMS II/ACS fire rate signal to the two boilers reaches a value
three times that of the start level percentage, the BMS II/ACS will call on the third boiler to begin
firing one module, and the BMS II/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 BMS II/ACS will call on the BCM of the fourth boiler to turn on
one module. At this point, the BMS II 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 BMS II/ACS in a reverse
manner. Whether the BMS II/ACS is set in a Constant Temperature or Modulating Temperature
mode, it will use the modulating ability to prevent header temperature fluctuation and maximize
efficiency. As well, the BMS II/ACS can stage auxiliary equipment such as combustion air
dampers and fans. Refer to BMS II Operations and Maintenance Manual GF-124/ACS Manual
GF-131, and Product Spec BMS-II for details.