Do I have an overly demanding flow switch(?) on boiler?

[WaterTight]

Caveat: I don't do boilers so no idea about them. My flow switch comment is pure guesswork based on zero understanding.

If I turn my kitchen mixer tap on hot, fully on, cold fully off, about 75% of the time the combi fires up and produces hot water for a bit but will then cut out. I am not mixing cold in at any point. But if I also turn on the bathroom hot tap a tiny at the same time as the kitchen hot tap it will reduce the flow to the kitchen tap, obviously, but it will stay hot.

The same occurs on the overhead rain shower head on the shower, although less so. With this turned on it can cut out but is more likely to fluctuate, like as if it's kicking in and cutting off repeatedly. If I open the basin hot a tiny bit at the same time as the rain shower head it does same as in kitchen, reduces flow a little bit to shower but then will stay consistent temperature.

The basin hot tap if used by itself stays hot and so does the non-rain shower head, the handheld one. Both of these outlets appears to produce less restricted flow than the kitchen mixer (flow looks good but has an aerator so in reality is slightly reduced) and the rain shower head (slightly restrictive I guess.)

But the flow out of every outlet, used on it's own, is more than sufficient for normal use. So it makes me think the boiler's requiring too great a flow before it kicks in...so something like a failing/faulty flow switch?

I have cover so can get someone out but just wanted to see what the general consensus was first.

Thanks

 

[Aquarius]

It would be an idea to state what make and model of boiler, not all of them have a flow switch, some are a flow turbine. Is the cold mains god enough to kick start the boiler, is there any peak demand issues?

 

[WaterTight]

It would be an idea to state what make and model of boiler, not all of them have a flow switch, some are a flow turbine. Is the cold mains god enough to kick start the boiler, is there any peak demand issues?

It's a Baxi Duo-Tech Combi HE

I've lived here for nearly 3 years and the problem only started in last year or so. All the taps and shower have been changed during that period but I don't believe the problem occurred immediately.

Peak demand may be something? Although not sure how you discover this. I do know one mains stopcock on the road outside turns of the supply to two flats and one house. Probably about 8 people in total. And it's a fairly densely populated road.

But at no point does the flow produces from outlets appear insufficient. Always seems like good flow to me.

 

[oz-plumber]

Some mixer taps are adjustable.
Unless you remove the handle and adjust the sprocket on the mixer, they will always let some cold water through. ( if your tap has this option )
Also, the low fire on you gas boiler may be over calibrated.
It may not be able to get low enough to maintain a minimal flow of hot water.

 

[Scott_D]

Is the flow from the taps low - some boilers don’t fire up below a set Lpm maybe 3

u think the Duotec has a flow turbine and Hall effect sensor that should light up red

 

[Aquarius]

As per @scott_d, check the Hall effect sensor operates each time, and make sure it’s on correctly. You can remove the front case off this boiler, without being gas safe registered.

 

[WaterTight]

Some mixer taps are adjustable.
Unless you remove the handle and adjust the sprocket on the mixer, they will always let some cold water through. ( if your tap has this option )
Also, the low fire on you gas boiler may be over calibrated.
It may not be able to get low enough to maintain a minimal flow of hot water.

They taps in question have standard full turn compression tap valves and rubber washers. So guessing these aren't going to let cold through when just hot is being operated?

 

[WaterTight]

Is the flow from the taps low - some boilers don’t fire up below a set Lpm maybe 3

u think the Duotec has a flow turbine and Hall effect sensor that should light up red

It's not super powerful, don't know how many lpm, will check.

 

[WaterTight]

As per @scott_d, check the Hall effect sensor operates each time, and make sure it’s on correctly. You can remove the front case off this boiler, without being gas safe registered.

Not sure I'll get involved with that as beyond my understanding and it's got cover anyway.
But thanks for the tip.

 

[king of pipes]

More likely to be partial blockage in the plate heat exchanger on the heating side, is the system clean ?, have a mag filter fitted , chemical inhibitors added ??, i have quite a few of these i service and work on and very rarely have issues if you service e properly. Kop

 

[ShaunCorbs]

Looks like new kop

 

[king of pipes]

Looks like new kop

6 years old Shaun stripped every year