Combi Hot water trigger

[Alan51]

First time living in a house with a combi. When I run the cold tap it triggers the combi hot water setting, I've checked the pipes and they are all connected correctly. The combi is just over a metre from the cold tap, is this just the slight pressure drop triggering as the boiler is so close to the tap. It's a Main boiler.

 

[fixitflav]

Does the water get hot?

 

[muggles]

Yes. A single check valve fitted to the cold inlet to the boiler will cure it

 

[Alan51]

Does the water get hot?

Yes nice and hot.

 

[ianmcd]

Yes nice and hot.

Not what he meant , he meant does the cold water get hot when the boiler false fires,Do as @muggles suggests fit a single check valve on the cold water inlet below the boiler

 

[fixitflav]

Not what he meant , he meant does the cold water get hot when the boiler false fires

That's right

single check valve on the cold water inlet below the boiler

So is firing for hot water triggered by a fall in pressure? Seems odd as the mains could be at a range of pressure. Unless the pressure switch setting is adjusted on commissioning. I always assumed there is a hot water flow switch.

 

[Alan51]

That's right

So is firing for hot water triggered by a fall in pressure? Seems odd as the mains could be at a range of pressure. Unless the pressure switch setting is adjusted on commissioning. I always assumed there is a hot water flow switch.

I've just checked and it fires only after the cold tap is turned off, I'll fit the single check valve, to be honest nothing surprises me with this house, it was a rental for decades and I don't think the landlord spent one penny more than he had to. It must have broke his heart when the boiler was replaced in 2016.