Harsco Industrial C1500H Installation & Owner's Manual page 15

3.4.3 High Voltage (TB2) Terminal Block
output pilot duty loads only. Do not connect any 120VAC supply voltage to the high voltage (TB2) terminal block.
Connecting a 120VAC supply voltage to TB2 can result in serious injury or death.
120 VAC Neutral- These terminals provide the neutral wires for the boiler 120 VAC outputs.
TB2 high voltage terminal block
120VAC Switched Output- This contact closes when the boiler is switched on. This provides 120 VAC, 0.5 Amp
service to TB2-10. The neutral for this circuit is provided on TB2-3. When the boiler is switched off, this terminal is
switched off as well.
3 Way Valve- This output is normally energized, keeping the three way valve open, 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 120 VAC, 0.5 Amp service to TB2-11. The neutral for this
circuit is provided on TB2-4. Note: the 3 way valve is a field sourced part.
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 the post pump time parameter within the DHW settings. This output
provides 120 VAC, 0.5 Amp service to TB2-12. The neutral for this circuit is provided on TB2-5.
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 the post pump time parameter within the CH settings. This output provides
120 VAC, 0.5 Amp service to TB2-13. The neutral for this circuit is provided on TB2-6.
Damper Relay - This output is enabled when the call for heat is enabled. This output provides 120 VAC service to
TB2-14. The neutral for this circuit is provided on TB2-7. This circuit is for pilot duty only.
Master Alarm Relay – This is a dry set of contacts that are normally open and will close in the event of an alarm
output from the boiler control, connecting TB2-15 and TB2-16.
Flame Detected Relay – This is a dry set of contacts that are normally open and will close whenever the boiler
control is reading a flame, connecting TB2-17 and TB2-18.
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For MACH C3000/C4000 boilers, the high voltage (TB2) terminal block is for 120VAC
TB1 low voltage terminal block
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MACH Gas Fired Boiler