AERCO C-More Controls Manual June 2010 - Manual (Page 99)

C-More Controller for Benchmark, Innovation & KC
USER MANUAL
04/22/14 AERCO International, Inc. • 100 Oritani Dr. • Blauvelt, New York 10913 Page 99 of 162
OMM-0032_0E Phone: 800-526-0288 GF-112
SECTION 9 - AERCO Boiler Sequencing Technology (BST)
9.1 INTRODUCTION
This Section applies only Benchmark boilers, but does not apply to Innovation water heaters.
The C-More on-board Boiler Sequencing Technology system (BST) is an integrated 8 boiler
control system incorporated into the C-More controller. The BST has its own sophisticated PID
control system designed to simultaneously control the light off and modulation of up to 8 boilers
while achieving maximum operational efficiency.
9.1.1 New AERCO BST Features
The following are new and innovative features incorporated into the AERCO BST:
1. One Boiler Mode
The “One Boiler Mode” eliminates excessive cycling in the Boiler Management System due
to low flow conditions.
A common and difficult to solve problem that results in excessive cycling occurs in a multi-
boiler system when a header sensor is mounted remotely downstream from any of the
boilers, and a “low-flow” condition exists.
NOTE
It is recommended that that the Header Sensor be installed within
2-10 feet downstream of the last boiler’s outlet.
Due to low-flow and the distance of the header sensor, changes in header temperature
cannot be detected in sufficient time to precisely control temperature. The excessive delay
in detecting temperature changes by the header sensor causes boiler firing rates to
continuously drop and rise, thereby “chasing” (or hunting) the desired setpoint.
The “One Boiler Mode” is an innovative and exclusive feature in On-Board BST that detects
a “low-flow” condition in a multi-boiler system. When BST determines that a low-flow
condition exists, it will slowly shut down one boiler at a time in an attempt to raise the Fire
Rate of the remaining boilers. If the low-flow condition persists and only a single boiler
remains ignited, BST will use the “Outlet Temperature Sensor” of the remaining ignited
boiler to control the temperature. The Outlet Temperature Sensor is mounted in the
individual boiler and drastically increases the response time to precisely control
temperature.
With Isolation Valves Installed
In One Boiler Mode with isolation valves installed, the master will use the ignited boiler’s
Outlet Temperature sensor for PID control. The distant Header Temperature Sensor is
monitored, but not used for control in this mode of operation.
Without Isolation Valves Installed
In One Boiler Mode with no isolation valves installed, the master will take the average value
of the Header Temperature and the ignited boiler’s Outlet Temperature for PID control.