Sime
Chronic Pressure Loss
System pressure drops over time without visible leaks; furnace frequently locks out on low pressure.
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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
Hidden leak in pipework, Leaking plate heat exchanger to DHW side, Faulty automatic air vent, Micro‑leaks at joints
How to Fix / Troubleshooting
Safety first: Turn off power before inspecting internal components.
- Monitor pressure: Note the pressure when cold and after heating. Rapid drops suggest a significant leak.
- Check discharge pipes: Look at the pressure relief valve discharge pipe outside; continuous dripping indicates a faulty valve or expansion issue.
- Inspect automatic air vent: Check for dampness around the air vent on top of the Sime furnace. Replace if leaking.
- Plate heat exchanger test (technician): A technician can isolate and test the plate heat exchanger for internal leaks into the DHW circuit.
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Repair Difficulty
Hard
4/5
Required Part
Pressure Relief Valve / Automatic Air Vent / Plate Heat Exchanger
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