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6
Wiring
Electrical wiring connections
The control box and all other electronic control system
components are installed on the APW water heater prior to
shipment from the factory. Therefore, electrical connections
to the electronic control system basically consist of connecting
external AC power to the electronic control system control
box. The system can be powered by a single-phase AC voltage
of 120 VAC, 60 Hz. However, if the electronic control system
was ordered with the ModBus Communication option,
several additional signal lead connections will need to be
made inside the control box. These signal leads will permit
the electronic control system to be controlled by an external
Energy Management System (EMS), Building Automation
System (BAS), or computer. Proceed as follows:
1.
Open the junction box on the side of the control box.
2.
Route the power wiring harness into the junction box
through one of the knockouts as shown in FIG. 6-1.
3.
Connect 120V power supply to the wires in the junction
box:
• Black - Live
• White - Neutral
• Green - Ground
Figure 6-1 Junction Box
Use a minimum of 14 AWG wire for AC
NOTICE
power wiring connections to the electronic
control system control box.
4.
If ModBus is not used, no further steps are required for
the APW. If no further connections are required, re-secure
the junction box door (FIG. 6-1).
20
JUNCTION BOX
DIR #2000577455
Indirect Plate Water Heater Installation & Service Manual
⚠CAUTION
NOTICE
NOTICE
DO NOT route ModBus communication
wiring in the same conduit as power
wiring. Attempting to do so may result
in excessive noise on the signal lines.
Also, ensure that the RS232 or RS485
signal cable connections do not exceed
the following lengths:
RS232 Cable: 50 feet maximum
RS485 Cable: 4,000 feet maximum
The complete wiring diagram for the APW
electronic control system is provided in
Section 11 of this manual.
The manufacturer recommends that
shielded, twisted-pair cable be used for
communication wiring.
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