Ariston Genus 27 BFFI Plus Boiler - Hot water issue

[jamesswallow89]

I moved in to my house 2 years ago and changed the taps in the kitchen to a mixer tap. Since then I can't get hot water out of the mixer tap. I believe it is due to the mixer tap not allowing as much flow as the original tap. However this has now started happening in the bathrooms. What I have discovered is that if I run two hot water taps at the same time I can get hot water, but just one at a time doesn't seem enough flow to get hot water.

I therefore believe my Ariston Genus 27 BFFI Plus Boiler is requiring more flow than usual to trigger the hot water, as time goes on this seems to be getting worse. Any recommendations on what the issue could be and what part of the boiler might be causing this issue?

 

[JohnD]

Two years without hot water?

Gosh!

Do you mean water comes out but the boiler does not fire up?

Please post a photo of this tap

And the pipework under the sink that connects to it.

Fill a bucket. Time it. Calculate litres per minute.

 

[DP]

Run a cold tap elsewhere when asking for hot water. See if that makes a difference.
What is the flow rate of hot water and also cold water out of the tap

I woukd also check the charge in the small expansion vessel on that boiler.

 

[jamesswallow89]

 

[jamesswallow89]

From the tap set to hot I get 4.6 Litres per minute
From the tap set to cold I get 5.5 Litres per minute

Running a cold tap elsewhere didn't make any difference.

At first I thought the new tap was at fault but as mentioned this is now happening elsewhere in the house, for example I can only get hot water from the shower if I run the nearby sink hot tap at the same time.

I have a bike tyre pump with a gauge and the expansion vessel has the same connection on top. Can I check and increase the pressure with this?

Also is it best to check this when the boiler is not running?

 

[jamesswallow89]

Okay so I checked the pressure of the small expansion vessel with a bicycle pump and it's at 1.1Bar. Can't seem to increase the pressure with the bicycle pump though

 

[jamesswallow89]

Also the boiler does not fire up when I run the hot tap, however this boiler has a storage tank inside so i'm not sure it would always fire up straight away

 

[DP]

I am familiar with the boiler
Fitted one many years ago and looked after clutch of these

You close the cold water stop valve till there is no water flowing from the hot tap. Then pressurise the expansion vessel

The cylinder has a sacrificial anode that should be changed if it not.

Cold water flow is very poor. Is this off the mains?

Boiler is badged to provide over 19 l per minute

 

[jamesswallow89]

Yes the flow is off the mains.

Looks like the expansion vessel should be pressurised to 3.5 Bar??

With the expansion vessel pressurised correctly, am I still likely to struggle to get hot water if the flow no where near 19l/m?

 

[DP]

Yes the flow is off the mains.

Looks like the expansion vessel should be pressurised to 3.5 Bar??

With the expansion vessel pressurised correctly, am I still likely to struggle to get hot water if the flow no where near 19l/m?

Boiler is like having a Ferrari ( not that that heap of a boiler can ever be regarded as the best out there) and a road to drive on is limited to 10 MPH

 

[jamesswallow89]

Re pressurised the DHW expansion vessel from 1.1 Bar to 3.5 Bar, still no change

Any other ideas please?

 

[DP]

Re pressurised the DHW expansion vessel from 1.1 Bar to 3.5 Bar, still no change

Any other ideas please?

The vessel ( while it can cause discharge) has little to do with your problem.
You need to look at the cold water supply pressure. Is the cold water off the mains or cold water cistern

 

[jamesswallow89]

The cold water is off the mains, however I don’t think this is the issue as I got hot water from the other taps before and this has slowly deteriorated. Could there be another element of the boiler causing this? I feel the boiler is wanting to see too much flow before it triggers the hot water