Harsco Industrial SC-2000 User Manual Download

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Gas Fired Boiler

Harsco Industrial, Patterson-Kelley Technical Service 1.877.728.5351

3.4.3 Low Voltage (TB1) Terminal Block

Enable/Disable

–

TB1-1

and

TB1-2

can be used to remotely enable or disable the boiler. The functionality of

these terminals is user-configurable through the NURO controls, but generally closure of the Enable/Disable
circuit provides a call for heat to the boiler. Opening this circuit prevents the boiler from running.
The boiler ships with a factory-installed jumper across the Enable/Disable terminals. This circuit is energized
with a

24VAC

potential, so the contacts on any remote enable devices must be rated for minimum

24VAC

4-20mA Analog Input

–

TB1-3

and

TB1-4

can be used to provide a remote analog 4-20mA control signal to the

boiler. This analog signal can be used to change the boiler’s operating setpoint or firing rate.

Spare Analog Input

–

TB1-5

and

TB1-6

are reserved for future use.

HDR Temp Sensor

–

TB1-7

and

TB1-8

can be used to connect a remote header temperature sensor, installed

in the primary hydronic system piping, downstream of all the boilers. This temperature sensor must be a 2-wire
12k

Ω

NTC thermistor. This circuit is energized by the boiler with a

5VDC

potential.

DHW Stat/Sensor

–

TB1-9

and

TB1-10

can be used to connect either an aquastat or remote DHW temperature

sensor installed in a domestic hot water storage tank. If using an aquastat, use a SPST normally-closed, break
on rise type with either a fixed or adjustable deadband above and below the setpoint.
Alternatively, if using a temperature sensor, it must be a 2-wire 12k

Ω

NTC thermistor and be of sufficient length

to measure an accurate storage tank temperature. This circuit is energized by the boiler with a

5VDC

potential.

Outdoor Temp Sensor

–

TB1-11

and

TB1-12

can be used to connect an outdoor air temperature sensor which

allows the NURO control to be programmed to run an outdoor air schedule. The outdoor air temperature sensor
must be a 2-wire 12k

Ω

NTC thermistor and should be installed on the North face of the building and shielded

from direct sunlight exposure. This circuit is energized by the boiler with a

5VDC

potential.

Night Setback

–

TB1-13

and

TB1-14

can be used to connect a day/night or occupancy timer. Closure of the

Night Setback circuit enables the Night Setback mode which reduces the boiler’s operating setpoint. Opening
this circuit resumes normal operation. This circuit is energized by the boiler with a

5VDC

potential, so the contacts

on the day/night timer must be rated for minimum

5VDC

4-20mA Analog Output

–

TB1-15

and

TB1-16

provide a 4-20mA analog output signal which tracks the boiler’s

firing rate. When operating at full power (maximum firing rate), the boiler will provide a 20mA output. When
operating at mimimum power (minimum firing rate), the boiler will provide a 4mA output.

Ground

–

TB1-17

provides an equipment (frame) ground connection for input, output, or communication

connections. For independently powered control devices, it may be necessary to create a common ground.

Cascade Shield & Cascade

–

TB1-18

TB1-19

and

TB1-20

can be used to setup a cascade system with multiple

SONIC boilers with NURO controls. Terminals

TB1-19

and

TB1-20

are reserved for the cascade communication

between the master and member boilers. Terminal

TB1-18

should be used to connect the cascade

communication wiring shield between all boilers. The cascade and shielding must be wired from the master
boiler to each individual member boiler in a daisy-chain fashion.

NOTE

: Only ground the shield at the master

boiler.

MODBUS COM & MODBUS Shield

–

TB1-22

TB1-23

and

TB1-24

can be used to integrate the boiler with a

Building Management System (BMS), Protocol Converter, or other device capable of RS-485 2-wire MODBUS
communication. Terminals

TB1-22

and

TB1-23

are reserved for MODBUS and terminal

TB1-18

provides a

connection for the MODDBUS communication wire shield.

NOTE

: Only ground the shield at the master boiler.

ECOM 1, 2 & 3

–

TB1-25

TB1-26

and

TB1-27

can be used to connect a wireless outdoor air temperature sensor.

The wireless receiver should be installed at or near the boiler, and the wireless temperature sensor should be
installed on the North face of the building and shielded from direct sunlight exposure.

Refer to

Section 6.1

for proper wiring and configuration of the electrical connections.