Harsco Industrial 1004905923 Installation & Owner's Manual page 11

NOTICE! A dedicated earth ground (green wire) is required to avoid nuisance shutdowns. Do not ground
through the conduit. It is also important that proper polarity be maintained.
The junction box at the rear of the boiler contains terminal strips for all customer connections. A detailed
schematic of the connections is shown in 6.1.7. These connections are described as follows:
High Voltage (HV) Terminal Block
The boiler power circuit requires 208-240 volts, single phase, 60 hertz, with a dedicated neutral and ground for
the control circuit as labeled. The voltage from each line (L1, L2) to the neutral must be approximately 120V AC.
Electrical service must be rated for 17 amps minimum. Before starting the boiler, check to ensure that the proper
voltage and amperage are connected to the boiler and that the boiler is connected to a suitable fused disconnect
switch or circuit breaker. There must be less than 1.0V from Neutral (HV-3) to Ground (HV-10)
120VAC Switched Output- This contact closes when the boiler is switched on. This provides 120VAC 5Amp
service to HV12 and HV13. The neutral for this circuit is provided on HV4 and HV5. When the boiler is switched
off, these terminals are switched off as well.
3 Way Valve- This output is normally energized, keeping the three way valve providing heat to the building. The
Domestic Hot Water (DHW) call for heat de-energizes this circuit, causing the 3 way valve to self close, thereby
providing heat to the DHW loop. This output provides 120VAC 0.5Amp service to HV14. The neutral for this
circuit is provided on HV 6.
DHW Pump Relay w/Delay Off - This output is enabled when there is a call for DHW. When the call for heat is
removed, the output remains enabled for a period of time. This output provides 120VAC 0.5Amp service to HV15.
The neutral for this circuit is provided on HV 7.
Circ Pump Relay w/Delay Off - This output is enabled when there is a call for heat. When the call for heat is
removed, the output remains enabled for a period of time. This output provides 120VAC 0.5Amp service to HV16.
The neutral for this circuit is provided on HV 8.
Damper Relay - This output is enabled when the call for heat is enabled. This output provides 120VAC service
to HV17. The neutral for this circuit is provided on HV 9. This circuit is for pilot duty only.
Master Alarm Relay – This contact closes in the event of an alarm output from the boiler control, connecting
HV18 and HV19.
Flame Detected Relay – This contact closes whenever the boiler is firing, connecting HV20 and HV21.
Low Voltage (LV) Strip
Enable/Disable– Use for boiler enable. Closing this circuit allows the boiler to run. Opening this circuit prevents
the boiler from running, provided the remote/local enable switch is in the remote position. This circuit is energized
by the boiler. It has a 24VAC potential. Devices connected to these terminals must be rated for 24VAC
position. Do not connect safety devices into the Enable/Disable circuit.
Auxiliary Low Water Cutoff – These terminals are used for connection of a secondary low water cutoff used in
the system. This circuit is energized by the boiler. It has a 5V potential. Devices connected to these terminals
must be rated for 5V.
The remote/local switch bypasses the Enable/Disable (LV1 to LV2) when in the local
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MODU-FIRE Forced Draft Gas-Fired Boiler 2500-3000
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