Weird one

[WaterTight]

When I turn my kitchen hot tap on (little bit or on full, doesn't matter) it gets nice and hot and stays that way. When I then also turn on the cold side of the mixer even a tiny bit the boiler immediately stops calling for hot water and the water then eventually gets cold.

Turn the cold back off, calls for hot water, water gets hot again.

This doesn't happen at my bathroom shower mixer. It also doesn't happen if I have the kitchen hot on and turn on another cold tap somewhere else.

Any ideas?

 

[Ben-gee]

Need to fit a non return valve in the hot supply to kitchen tap.
Alternatively change tap to one with a dual flow spout.
Yours is mixing in the tap body and the cold pressure is overcoming the hot enough to slow the flow to the point where the combi goes off

 

[king of pipes]

As above 👍

 

[WaterTight]

Ah brilliant.

What's weird is I've read about this problem and solution on here before and yet never come across it with a customer so it was at the back of my head. Brilliant!

Thanks

 

[WaterTight]

Need to fit a non return valve in the hot supply to kitchen tap.
Alternatively change tap to one with a dual flow spout.
Yours is mixing in the tap body and the cold pressure is overcoming the hot enough to slow the flow to the point where the combi goes off

I will try this fix but a thought occured...the flow doesn't seem to be slowed at all as it happens even when I turn on the cold a tiny, tiny amount so overall flow barely perceivably changed.
But will try fix and report back

 

[Ben-gee]

Your flow out of the tap is not less, it’s the flow through the boiler that is less and hence this cuts out.

At the tap the cold has taken over like a big bully! So it rushes out of the tap , but also pushes back against the hot and gives you the problem you’ve got.