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Why does my Vaillant combi boiler heat up water when I turn on cold water?

Marax
Marax ✭
in General Questions & Topics

Hi everyone,

I have a Vaillant combi boiler (Vaillant ecoTEC plus VUI 26CS/1-5), and I’ve noticed that it starts heating up when I turn on the cold water tap. It does happen every time.

Recently, we installed a pressure regulator at the main water inlet to lower the pressure in the appartments building. It seemed to stop the problem, but we later had to increase the pressure again, and now the issue is back. Is there similar regulator directly on boiler?

I know the question should be for Vaillant not here for Tado. But there are many kind experts here at my fingertips.

Thanks in advance for your help!

Answers

  • policywonk
    policywonk ✭✭✭

    There is usually a pressure measuring device which checks for the flow of water to the taps. Best to contact Vaillant and ensure there is an engineer review of the pressure sensors on outbound water.

    Assuming your boiler is connected to an unvented supply line, a drop in pressure on the cold water pipes should not trigger the boiler to produce heat. It should only do that when there is a drop in pressure on the hot water pipes (meaning a tap is open).

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