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Noisy Grundfos pump on Vaillant EcoTec — vibration through whole house
Got a Vaillant EcoTec Pro 28 with what sounds like a noisy pump — low-pitched hum/vibration that's noticeable in all rooms. System is fully pumped, recently power-flushed. Inhibitor added. I've isolated the pump and re-started and it goes away briefly then comes back. Pump is about 3 years old. Is this a bearing issue or could it be something else causing the resonance?
2 Answers
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Also check the pump is fully bled. Air trapped in the pump housing causes exactly this kind of resonant hum. There's a bleed screw on the front of the UPM3 — just crack it with a flat-head until water runs out. Took me an embarrassingly long time to try that on my first one.
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On EcoTec Plus/Pro the Grundfos UPM3 pump can develop this hum after 2-3 years. First thing — check the pump speed setting. If it's on fixed high speed, drop it to Auto/variable. The variable speed often cures the vibration. If not, the pump is probably on its way out — they're not expensive and straightforward to swap.