Noritz Flow / Load Imbalance

Boiler shuts down when multiple heating zones call at once, but runs with a single zone.

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

Insufficient pump capacity, Incorrect zone valve sequencing, Undersized piping, Boiler flow switch tripping

Safety: System water may be hot; use caution.

1. Observe pump operation: Confirm the main system pump runs whenever any zone calls for heat.
2. Check zone valves: Ensure zone valves are not wired in a way that overloads the boiler or starves it of flow.
3. Balance zones: Throttle balancing valves if one zone is taking most of the flow.
4. Professional hydronic review: A heating contractor should verify pump sizing and piping layout and may recommend a primary/secondary piping arrangement for the Noritz boiler.

Hard 4/5

System Circulation Pump

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