Rheem
Low DHW Output Temperature
Boiler produces insufficient domestic hot water temperature (lukewarm water)
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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
Scaled domestic plate heat exchanger, Faulty DHW temperature sensor, Incorrect DHW setpoint, Flow rate too high for boiler capacity
How to Fix / Troubleshooting
Safety first: Turn off power and close domestic water isolation valves before servicing DHW components.
- Step 1 – Check DHW setpoint: Verify the domestic hot water temperature setting on the Rheem boiler control. Increase within safe limits if set too low.
- Step 2 – Reduce flow: Open hot taps partially and see if temperature improves. Excessive flow can exceed the boiler’s DHW capacity.
- Step 3 – Inspect and test DHW sensor: Check the DHW temperature sensor wiring and resistance. Replace if faulty.
- Step 4 – Descale plate heat exchanger: If DHW temperature is low despite correct settings and sensor, the plate heat exchanger may be scaled. A technician should chemically descale or replace it.
Warning: Do not set DHW temperature excessively high to compensate for faults; this increases scalding risk.
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Repair Difficulty
Medium
3/5
Required Part
DHW Plate Heat Exchanger
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