Boiler Sequencing Technology; Introduction; Installation Notes - Watts AERCO Edge CFR 3000 Operator's And Service Manual

Boiler with edge controller, natural gas modulating boilers

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SECTION 7 BOILER SEQUENCING TECHNOLOGY

SECTION 7. BOILER SEQUENCING TECHNOLOGY

The Boiler Sequencing Technology system (BST) is an integrated 16 boiler control system. It is built into

the Edge Controller. It has its own sophisticated PID control system designed to simultaneously control

the light off and modulation of up to 16 boilers while achieving maximum operational efficiency.

BST is designed to ensure that all Boilers in the system operate at maximum efficiency. This is

accomplished by lighting off boilers only when all ignited boilers reach or exceed a defined Valve

Position (Fire Rate). Operating all boilers below the defined Fire Rate "Next on VP" (for Next Turn on

Valve Position) ensures that they are firing at their most efficient Fire Rate. One unit the BST network is

defined as the "Manager" and all other units on the network are defined as "Client" units. The Manager

monitors the system Header Temperature, and monitors all Client unit's status information, efficiently

controlling all units in order to achieve and maintain the required BST Setpoint Temperature.

When there is a demand, the Manager will light off the lead boiler based on the BST Sequencing

selection in the BST Cascade Status screen. As system load increases and the valve position of the

ignited unit(s) reaches the Next on VP (% valve position), the Manager will light off the next available

unit. A simplified block diagram of multiple Boilers connected to a BST is shown in Figure 7-1 below.

NOTE: After boiler load is satisfied, the isolation valve remains open for a programmed interval (default = 2

minutes) before closing. When system load is satisfied, the controller will open the isolation valves for all the

boilers. The BST controls the valves via a 0-20 mA signal.

A ProtoNode is needed for the LonWorks communications protocol. If your installation includes a

ProtoNode SSD (Client-Client Device), you must adhere to the procedure listed below. Failure to

complete these steps can result in the failure of the BST system.

a) Do NOT install the ProtoNode device at the outset of the installation. If the ProtoNode device is

already installed, you must physically disconnect it from the Modbus network on the I/O board.

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Figure 7-1: Simplified BST Block Diagram

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