Crown Boiler PHNTM399, Installation And Operating Instructions Manual

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Figure 30: Alternate “Immersion” type Header Sensor Installation Detail
VIII. Electrical
(continued)
G. External Multiple Boiler Control System
This boiler is equipped with a Honeywell R7910 Control
which has a built-in sequencer for multiple boiler
operation. The R7910 also accepts a 4-20mA input from an
external sequencer. Follow multiple boiler control system
manufacturer (Honeywell, Tekmar, etc.) instructions to
properly apply a multiple boiler control system.
H. Multiple Boiler Operating Information
1. Required Equipment and Setup
a. Header Sensor (Honeywell P/N 32003971-003).
A header sensor must be installed and wired
to the Master Sequencer “enabled” R7910
Controller. The header sensor is installed on the
common system piping and provides blended
temperature information to the Sequence Master.
Refer to piping diagram Figure 23A on page
45 for installation location and Figure 30 for
installation detail.
b. Ethernet Cables
Ethernet cables are used to connect the boiler
network together. These are standard “straight
through” cables that can be purchased at
electrical distributors.
Alternately, the network can be wired together
by simply wiring terminal J3, Modbus 2,
terminals A, B and V- between each boiler.
Refer to Figures 26 and 27 terminal J3 for wiring
location.
c. RJ45 Splitters
When Ethernet cables are used to connect three
or more boilers together, RJ45 Splitters are
required. When two boilers are connected the
splitter is not required.