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Installation & Operation
11.0 LEAD LAG INSTRUCTIONS
Multiple Boiler Applications
The FTG controller has the internal capacity to stage or Lead-Lag up to 8 boilers configured in a cascade. This
Lead-Lag capability allows a designated "Master" boiler to communicate with and effectively control each
boiler in a multiple boiler system. This function is accomplished by "Daisy Chaining" a 3-wire cable between
each of the boilers and enabling the Master parameter in the boiler of your choice. The boiler with the Master
parameter enabled becomes the single point of contact for Central Heating, Domestic Hot Water and Outdoor
Reset settings and control wiring. Use the instructions detailed in this section to set-up and install the cascade
boiler system; reference Appendix A – Controller and Touchscreen Display Instructions for details on more
advanced settings and for assistance with navigating the touchscreen display.
Lead Lag Instructions - Common
Plumbing – install as many as 8 FTG boilers in parallel in a primary/secondary plumbing configuration as
illustrated in Figure 11-1. Size common piping as per Table 11-1.
Boiler Pump – each boiler must have its own circulator (see Figure 11-1) which is controlled by its BOILER
PUMP output; see Field Wiring Figure 12-2 and Table 12-1. The Boiler Pump must be sized according to
Table 10-3.
Communication Wiring – using 3-wire cable, daisy-chain terminals LL DATA +, LL DATA – and COMMUN.
COM of each boiler in parallel; see Field Wiring Table 12-2 and Figure 12-3.
System Sensor (Optional) – install a system sensor (NTI P/N: 84010) on the outlet (supply) pipe feeding the
heating system, see Figure 11-1. Wire the system sensor to the SYSTEM SENSOR terminals of the Master
Boiler; see Field Wiring Table 12-2 and Figure 12-3. The system sensor automatically becomes the
modulation sensor for the boiler system, i.e. the control attempts to achieve setpoint temperature at the
location of the sensor. If a system sensor is NOT used, at the Master boiler set the applicable sensor input to
Unconfigured as follows:
Configure – Sensor Configuration – S10 (J10-7) sensor
Outdoor Sensor (Optional) – wire the outdoor sensor to the OUTDOOR SENSOR terminals of any one of the
boilers in the cascade; see Field Wiring Table 12-2 and Figure 12-3. Note: only one outdoor sensor is needed
for the multiple boiler system.
Modbus Address – assign a unique MB2 Modbus Address to each boiler in the cascade. Access the MB2
Modbus Address setting via the System Identification & Access menu as follows:
Configure – System Identification & Access – MB2 Modbus Address
Master Enable – choose one (and only one) boiler in the cascade to be the Master, this boiler will receive all
control wiring and will be used for setting control parameters (see steps below). On this one boiler, set
Master enable equal to Enabled via the Lead Lag Master Configuration menu, accessed as follows:
Configure – Lead Lag Master Configuration – Master enable
Table 11-1 Minimum Pipe Sizes for Multiple Boiler Applications
# of
Units
FTG 600
2
3 in.
3
4 in.
4
4 in.
5
4 in.
6
5 in.
7
5 in.
8
5 in.
Note: Minimum pipe size based on assumed temperature rise of 25ºF at maximum firing rate.
44
Manual│
FTG 800
FTG 1200
4 in.
4 in.
4 in.
5 in.
4 in.
5 in.
5 in.
6 in.
5 in.
6 in.
5 in.
6 in.
6 in.
8 in.
Model
FTG 1400
FTG 2000
4 in.
5 in.
5 in.
6 in.
5 in.
6 in.
6 in.
8 in.
6 in.
8 in.
8 in.
8 in.
8 in.
8 in.
FTG
FTG 2200
FTG 2400
5 in.
5 in.
6 in.
6 in.
6 in.
8 in.
8 in.
8 in.
8 in.
8 in.
8 in.
8 in.
8 in.
8 in.
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