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Installation & Operation Manual
48
8 Field wiring
Runtime contacts
The SMART SYSTEM control closes a set of dry contacts
whenever the burner is running. This is typically used by
Building Management Systems to verify that the water
heater is responding to a call for heat.
Alarm contacts
The SMART SYSTEM control closes another set of contacts
whenever the water heater is locked out or the power is
turned off. This can be used to turn on an alarm, or signal
a Building Management System that the water heater is
down. Note that the alarm contacts will close momentarily
after each call for heat.
Wiring of the cascade
When wiring the water heaters for Cascade operation, select
one water heater as the Leader water heater. The remaining
water heaters will be designated as Members. See page 56
“Configuration of the Cascade” for a detailed explanation of
this procedure.
Connect the tank sensor to the Leader water heater. For the
Cascade system to work properly the tank sensor must be
installed. The tank sensor should be wired to the low
voltage connection board at the terminals marked for the
tank sensor (see FIG. 8-3). The Leader control will use the
water temperature at the tank sensor to control the
operation of the Cascade.
Communication between the Leader water heater and the
Member water heaters is accomplished by using shielded,
2-wire twisted pair communication cable. Connect one of
the twisted pair wires to terminal A on each of the Low
Voltage Connection boards, and the other wire of the
twisted pair to terminal B on each of the Low Voltage
Connection Boards. Connect the shield wires to one of the
shield ground terminals on the Low Voltage Connection
Boards (FIG. 8-3). If more than two water heaters are on the
Cascade, daisy chain the wiring from the Sequencing
terminals on the second water heater to the Sequencing
terminals on the third water heater, then from the third to
the forth, and so on. The connections between heaters can
be made in any order, regardless of the addresses of the
water heaters. Try to keep each cable as short as possible.