H2
Peerless Return Temperature Too High / Delta-T Too Low

Boiler shows H2 and may shut down intermittently during long runs

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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.

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Possible Causes

Short-cycling due to oversized boiler, bypass piping causing high return temp, mixing valve misadjusted

How to Fix / Troubleshooting

Safety first: Be cautious around hot water piping.

Steps:

  • Check system design: Verify that any boiler bypass or primary/secondary piping is configured per Peerless installation manual.
  • Adjust mixing valves: If a mixing valve is installed, ensure it is not set too high, which can raise return temperature.
  • Increase flow: If possible, increase circulator speed to improve delta-T.
  • Consult a professional: Persistent H2 may indicate a design issue requiring re-piping or control adjustments.
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Repair Difficulty

Medium 3/5

Required Part

Mixing valve
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