Appendix E Falcon Lead Lag
E-5
When combining controllers with different software versions in a Falcon lead/lag net-
work, choose one with the most recent software revision as the Master Host (see Sec-
tion 4).
• Modbus network connecting all Falcon boiler controllers in the system.
• System header pressure sensor (required for lead lag operation).
• 833-05105 or 833-03577 display for each boiler.**
A Falcon lead lag kit (880-3755 for 15# steam or 880-3756 for 150# steam) is available from
Cleaver-Brooks and includes a system header pressure transmitter and Falcon Program Module for
copying parameter settings from one Falcon to another.
* Software version 3468.2550 or later required.
** If 833-03577, software version 1.4.2 or later required.
3- SPECIFICATIONS
• Maximum length of Modbus network (18 AWG 2-conductor shielded or twisted pair
cable): approx. 600 ft (200 m). NOTE - terminating resistors may be necessary for long
cable runs.
• Lead lag Modbus baud rate: 38400
• EMS Modbus baud rate: user selectable (9600, 19200, 38400)
Refer to appropriate manual for control component environmental specifications.
For more on the Modbus protocol, visit www.modbus-ida.org.
4- FEATURES
Falcon controllers connected in a lead lag network use the Modbus communication bus to
communicate in a ‘Master-Slave’ configuration. The ‘Master’ is a software management service and
is ‘hosted’ by one of the Falcon units in the network. The lead lag Master is not a separate controller
and no additional control panels or devices are required to configure and operate a Falcon lead lag
network. The Master is responsible for all high-level system functions including boiler sequencing
and staging, pump/valve control, and system PID setpoint control.
• PID setpoint control - The lead lag Master uses a proportional-integral-derivative algorithm to
maintain system header temperature at a setpoint. Individual boilers are turned on and off as
necessary according to the configured sequence and add/drop-stage methods. PID gain settings
are user-configurable.
• Outdoor reset (hot water systems) - Adjusts the setpoint according to outdoor temperature. Uses
an outdoor temperature sensor wired to one of the lead lag slaves’ sensor inputs.
• Time of day setpoint (night setback).
• Remote enable - system can be enabled from a separate boiler room controller or building energy
management system (EMS).
• Remote setpoint (hot water)
• Warm weather shutdown (hot water) - uses the outdoor temperature and shuts down the lead lag
system at a setpoint (plus a 4 deg F hysteresis). Can be programmed to shut down immediately
or when current demand for central heat ends.
• Frost Protection (hot water) - when an individual slave requires frost protection it notifies the lead
lag Master, which will then activate a pump or if necessary fire a burner.
• Pump control (hot water) - 3 configurable relays on each Falcon controller can be controlled in
conjunction with the lead lag Master.
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