Appendix E Falcon Lead Lag
E-39
LEAD LAG OPERATION
Reference Manual
Contents
General Description of the Lead Lag Application .........E-39
Lead Lag (LL) Master General Operation .......................E-39
System Wiring Hookup ....................................................E-42
Lead-Lag Operation...........................................................E-43
Slave Operation and setup ..............................................E-44
Slave Parameters ..............................................................E-45
LL Master Operation and Setup ......................................E-46
Many of the descriptions used herein refer to functions or tables internal to the Falcon. Only those functions
specifically identified as ‘parameters’ are user-configurable.
GENERAL DESCRIPTION OF THE LEAD LAG APPLICATION
The CB Falcon can operate in one of three ways - as a stand alone control, as a Lead Lag Master (and simultaneously
a slave) or solely as a slave in a lead lag system. The lead lag master should be thought of as a software function that
oversees each individual Falcon control in the network, including the one that hosts it. The master sees each slave
(inccluding the one hosting it) as a set of Modbus devices, each having certain registers. In this regard the lead lag
master can be considered as essentially a communications bus device, talking to the slave Falcon controls via
Modbus.
Falcon devices utilize two ‘ModBus™’ ports (MB1 and MB2) for communications. One port will be designated to
support a system display and the other port will support communications from the LL Master with its slaves. The
diagram on page 4 shows a simplified wiring diagram with a 4 system Lead Lag arrangement.
The LL master uses a few of the host unit's sensors (header temperature and outdoor temperature) and also the STAT
electrical inputs in a configurable way, to provide control information.
LEAD LAG (LL) MASTER GENERAL OPERATION
The LL master coordinates the firing of its slave units. This involves adding or dropping stages as needed to meet
changes in load, and sending firing rate commands to those units that are firing.
The LL master turns the first stage on and eventually turns the last stage off using the same criteria as any modulation
control loop:
• When the operating point reaches the Setpoint minus the On Hysteresis, then the first Falcon is turned on.
• When the operating point reaches the Setpoint plus the Off Hysteresis then the last slave Falcon (or all slave units)
are turned off.
The LL master PID operates using a percent rate: 0% is a request for no heat at all, and 100% means firing at the
maximum modulation rate.
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