Vaillant turbomax 282e - low CH pressure

[aris]

This is on a closed system for the CH water. I notice that the pressure goes way low - almost to zero. When the CH comes on, it goes way up again - to just above 2 (which I suspect is my mains water pressure).

I thought there could be a leak in the CH - and even bought some Fernox F4 (though I have not used it yet).

Any idea what could be wrong here?

Last year I replaced both the heat exchanger and the diverter valve.

 

[jackthom]

If the pressure increases considerably as the water in the heating circuit warms up it's likely a problem with the expansion vessel See if this FAQ helps.

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