Main Multipoint - Water Runs Hot & Cold

[scousegit]

I had a Main Multipoint water heater fitted 4 years ago. From day one, the hot water from the taps runs hot for a minute or two, then goes cold for about a minute, then starts running hot again for a couple more minutes.

This wil continue, hot then cold for as long as the tap is running. The boiler heat control is set about half way.

Is this normal for these, or is there a fault?

Many thanks for any help.

 

[Softus]

If the flow rate is such that the boiler reaches the set temperature, then it will go out until the water is cooler.

Have you tried turning up the thermostat so that it will stay lit for longer?

If you find that the water is then too hot, then you'll need a blending valve to mix the water down to a usable/safe temperature.

 

[ChrisR]

Is the water supply flow rate too low? Should be about 10 litres/minute at least, iirc.

 

[courage best]

Thanks for the replies.

Will try turning up the stat.

As for flow rate, its really good, about the same as the mains water.

 

[gas4you]

Why have you put up with for 4 years already