IBC Standby Pump Overrun / Ghost Flow

Boiler cycles on and off while maintaining a constant low-level noise even when there is no call for heat or hot water.

Safety Warning

This repair may involve working with high voltage components or water connections. Always unplug the appliance before removing any panels.

If you are not confident in your ability to perform this repair safely, we strongly recommend contacting a professional technician.

Possible Causes

Pump overrun setting too long, External controls backfeeding power, Check valves leaking causing unwanted circulation, Incorrect wiring of pump relays

How to Fix / Troubleshooting

Safety: Turn off power before inspecting wiring.

Review pump overrun: In the IBC control menu, check the pump overrun time. Adjust to manufacturer-recommended values.
Check external controls: Ensure external relays or zone controls are wired according to IBC schematics and are not feeding power back to the boiler pump output.
Inspect check valves: If heat migrates into zones when there is no call, check valves may be leaking and should be replaced.

If behavior is unclear, a technician should review the control strategy and wiring diagram.

Repair Difficulty

Medium 3/5

Required Part

Internal System Pump

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