Connect 120 V power for CH and DHW circulators

What is going on

Field wiring for the central heating and domestic hot water pumps at the boiler junction box. The 120 V circulator cables land on CN5 for the CH pump and CN4 for the DHW pump. It is simple work, but it is line voltage and gas is on the unit.

Likely causes

• New install where external circulators are being added
• Replacing a circulator or its cable
• Rewiring after a cable was damaged
• Switching to external pumps from internal ones

Check in this order

1. Shut off power at the boiler and at the circuit breaker, then verify it is dead with a meter.
2. Shut off gas at the manual shutoff.
3. Remove the boiler front cover.
4. Disconnect the three clips and open the junction box.
5. Feed the circulator power cable through the side panel hole and secure it with a strain relief or conduit hub.
6. Connect the cable to CN5 for the CH pump and CN4 for the DHW pump.
7. Check that the new cable sits correctly inside the control panel.
8. Reconnect the junction box cover and reinstall the front cover.
9. Restore gas to the boiler.
10. Restore power to the boiler and run both pumps to confirm.

More boiler guides

• Access the low voltage wiring connections
• Blocking errors versus lockout errors
• Blower not running
• Blower runs at high speed with burner off
• Boiler bangs or hisses; Lockout 81 delta T
• Burner not running on a call for heat