Burnham
Poor DHW Performance
Domestic hot water from indirect tank is insufficient or runs out quickly
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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
Failed DHW circulator, Scaled indirect tank coil, Incorrect DHW priority settings, Faulty tank aquastat or sensor
How to Fix / Troubleshooting
Safety first: Turn off power before working on circulators or wiring. Hot water can scald.
- Check boiler firing on DHW call: Run hot water and see if the boiler indicates a DHW call and fires to high output.
- Verify DHW circulator: Feel the DHW pump when there is a call; it should vibrate and get warm. If not, check its power and relay.
- Inspect tank aquastat/sensor: Ensure the sensor is properly attached to the tank and set to an appropriate temperature (typically 120–140°F).
- Check mixing valve: If a thermostatic mixing valve is installed, a stuck or misadjusted valve can limit hot water. Adjust or replace as needed.
- Descale coil: A heavily scaled coil in the indirect tank reduces heat transfer. A professional can flush or descale the coil.
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Repair Difficulty
Medium
3/5
Required Part
DHW Circulator Pump
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