combi boiler not kicking in

[Trampy]

Hi all,
i'm relatively new to the world of plumbing and bathroom fitting.
I've recently fitted a bathroom and the new basin tap (Bristan Orta Mixer) wont kick in the boiler when the hot is turned on. The new bath mixer and the existing kitchen tap work fine although the hot has to be turned fully on to kick the boiler in.
Is this likely to be a flow issue as the pressure in the new basin tap is pretty poor. I've not changed any of the existing pipework, I've used full bore isolating valves and have ensured that the tap tails aren't twisted or kinked. I also dismantled the tap and made sure the filters were clear.
Or could it be an issue with the boiler?
cheers

 

[Old Account]

What type of boiler is it?

 

[Trampy]

What type of boiler is it?

It's a combi boiler

 

[Sharp Point]

It's a combi boiler

😛.... yes we gathered that from the title, I think matchless means make and model.

 

[Trampy]

😛.. yes we gathered that from the title, I think matchless means make and model.

not sure, I’ll find out tomorrow

 

[Sharp Point]

You say filters, have you cleaned the aerating insert on the tap outlet spout?

 

[Trampy]

You say filters, have you cleaned the aerating insert on the tap outlet spout?

Yes, I cleaned that too

 

[Gasmk1]

Try it without the spout insert see if it works as some do really restrict the flow

 

[Trampy]

Try it without the spout insert see if it works as some do really restrict the flow

Ok thanks, I’ll try that

 

[Stu-B]

Sounds like a boiler problem to me if you need to open the hot fully in the other taps to get it to fire, what’s the cold flow rate like?

 

[Millsy 82]

What's the flow rate like out of the taps?

 

[Burger]

Have you checked that you opened the stopcock fully? As everyone else, check your flow rates.

 

[Trampy]

Try it without the spout insert see if it works as some do really restrict the flow

So I removed the spout insert and the water came gushing out and the boiler kicked in!! But water now splashes all over the bathroom I’ve seen online you can get an adjustable aerator spout insert, are these any good? Or am I just going to get the same problems of either too low flow or water splashing everywhere?

 

[Trampy]

Have you checked that you opened the stopcock fully? As everyone else, check your flow rates.

Yes, stopcock is fully open

 

[Trampy]

Sounds like a boiler problem to me if you need to open the hot fully in the other taps to get it to fire, what’s the cold flow rate like?

Yes, I was thinking the same. The cold flow is good on the kitchen tap. It’s a messed up system though because the colds in the bathroom are tank fed.

 

[antoine irving]

You need to install check valve. The reason why the boiler doesn't "kick in" is because not enough water (hot leg) is flowing to activate the flow switch and its due to the fact cold water is pushing hot water inside the body of the mixer as cold water has more pressure , installing a nrv ideally on both hot and cold under the basin should solve your problem

 

[Sharp Point]

You need to install check valve. The reason why the boiler doesn't "kick in" is because not enough water (hot leg) is flowing to activate the flow switch and its due to the fact cold water is pushing hot water inside the body of the mixer as cold water has more pressure , installing a nrv ideally on both hot and cold under the basin should solve your problem

Sorry, that holds no weight. There’s millions of mixer taps on combi’s with no check valves that operate the boiler fine.

 

[Sharp Point]

Sorry, that holds no weight. There’s millions of mixer taps on combi’s with no check valves that operate the boiler fine.

And also, I’m sure he would’ve tried just hot water only..

 

[Zippymark]

ALSO a check valve will only slow the flow down further. The combi will need a certain amount of flow through it to activate it and fire it up. If it's a fairly old boiler with a diaphragm that detects flow, as these get old/scaled up they need more and more flow to kick in. Sorting that out would be a job for a gas safe engineer though. Or maybe the flow is terrible everywhere and you're fighting a losing battle.

 

[Trampy]

Thanks for all of your help on this matter. Eventually I discovered that Bristan supply different spout outlets for their taps. The one supplied with this tap was the lowest flow available so I changed it to the highest flow possible and it worked! The flow rate was increased considerably and the boiler now fires up.