Broadback wrote:

My Vaillant Turbomax Plus boiler is having problems supplying hot water.
The central heating is fine but the hot water,though it
works,intermittently goes cold. I first noticed it when using the
shower, I thought at first that the shower was at fault, however on
checking it also happens when running the hot taps. I have checked that
no one else is calling for hot water at the same time and have tried
adjusting the water temperature to no avail. At a guess it runs hot ok
for about 20 seconds then goes cold for 10 seconds. Any ideas please?

Does it continually go hot then cold then hot etc?
If so, possible hot water heat exchanger blockage - quite common
apparently..
Or, Primary heat exchanger fault, or possible pump failing - both less
likely, but possible..

Or does it run hot for 20 seconds, the stays luke warm?
That would point toward a divertor valve fault.

Alan.
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