Worcester 24i RSF-L Combi boiler problem

CRANEPB

Worcester 24i RSF-L Combi boiler problem:
When I turn the hot water tap on the boiler fires up and hot water is dispensed from the tap. However after a minute or two the water goes cold. Is this a diverter valve problem? The boiler also makes a noise after I have turned the tap off that sounds like it is trying to fire up / reset or something, but it can't make its mind up. The heating function of the boiler works fine. Can anyone please advise.

Thank you.

Agile · Posted: Wed Oct 08, 2008 10:22 am Post Subject:

It sounds as if the heat exchanger may be scaled up and causing overheat protection to be activated.

What happens if you leave it running after it goes cold?

It could also be a PCB fault or another component. Some people find these faults difficult to identify.

Tony

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CRANEPB · Posted: Wed Oct 08, 2008 1:54 pm Post Subject:

Thanks for the reply. We do live in a hard water area so a scaled up heat exchanger could be the problem. If this is the problem what would be the remedy? I will try running it after it goes cold tonight to see if it heats up again.

Agile · Posted: Wed Oct 08, 2008 9:59 pm Post Subject:

We would use a power flushing pump and sulphamic acid to descale it.

Unfortunately only a very few gas engineers would do this messy and time consuming procedure. We would charge £180 !

Others would change the HE at a cost of perhaps £150 plus labour ( at £120 ? ).

Tony

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CRANEPB · Posted: Thu Oct 09, 2008 10:39 am Post Subject:

Was unable to repeat the problem last night and the system worked fine. Obviously a problem is evident and I will have to monitor it.

Best Regards.

magicmanalex · Posted: Sat Oct 24, 2009 11:56 am Post Subject:

Hi there,

Was just wondering if you managed to diagnose this fault as I'm having the same problem with the same model boiler.

I had a plumber come out and look at it. He thought it may have been the air pressure switch and swapped it out for a new one, but the problem was still there.

It also makes a very rapid clicking noise, like there's a solenoid valve open and closing very quickly.

Thanks in advance.

Alex

bengasman · Posted: Sat Oct 24, 2009 1:06 pm Post Subject:

How often do you have to re-pressurise the system?
What is the pressure cold and hot?
What setting do you keep the boiler stat on?

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magicmanalex · Posted: Sun Oct 25, 2009 1:17 pm Post Subject:

Thanks for the quick response.

When the boiler's on, the pressure sits at about 1.3 bar, when it's off, it's normally at about 0.9 - 1.0 bar.

I don't have to pressurise it that often - the last time I did was a couple of months ago when I put back a radiator I had removed when getting the wall re-plastered.

This fault has existed before the radiator was removed though.

At the moment, the CH is set to hot, but this issue occurs no matter what the setting.

holty · Posted: Sun Oct 25, 2009 1:39 pm Post Subject:

not uncommon for pcb issues on these.the rapid clicking does sound like the gas valve solenoid.a decent rgi would find the problem, and not just change pointless parts till it works.

bengasman · Posted: Sun Oct 25, 2009 1:43 pm Post Subject:

Without being able to measure things, I would guess limescale to be the culprit; do you have hard water?

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magicmanalex · Posted: Sun Oct 25, 2009 1:51 pm Post Subject:

According to Northumbrian Water's website, the water is 'SLIGHTLY HARD'.

The measurement comes in at: 54 (Hardness in mg/l as calcium).

If limescale build-up is the problem, what's the recommended solution?

bengasman · Posted: Sun Oct 25, 2009 1:54 pm Post Subject:

magicmanalex wrote:

If limescale build-up is the problem, what's the recommended solution?

Fixed price repair.

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magicmanalex · Posted: Sun Oct 25, 2009 2:04 pm Post Subject:

Oh yes, sorry - somebody did mention a powerflush/acidic descale above. I forgot.

I don't know much about boilers, but would the engineer be able to check for limescale before proceeding with a power flush?

I'd hate to have to fork out something like 180 pounds for it to be flushed only to find out it's just the same and I then have to pay for a new PCB.

bengasman · Posted: Sun Oct 25, 2009 2:29 pm Post Subject:

magicmanalex wrote:

...but would the engineer be able to check for limescale before proceeding with a power flush?

I'd hate to have to fork out something like 180 pounds for it to be flushed only to find out it's just the same and I then have to pay for a new PCB.

That is why I mentioned a fixed price repair.

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magicmanalex · Posted: Wed Oct 28, 2009 5:34 pm Post Subject:

OK, so I took your advice and went for a fixed-price repair.

Called British Gas this morning who said £167.42 all-in, guaranteed for 12 months (existing customer). I was expecting them to say at least a couple of days. They were out within about 6 hours.

Turned out to be the PCB (£120 part online). The engineer didn't have one, but sent a text to all of the engineers in the local area to see if they had one available. No luck so he said he'd have to come back tomorrow. His line manager then called and authorised him to go and purchase one from a nearby seller (apparently BG have a 70% same-day fix target that they need to reach).

An hour later, here I am typing this in a really warm living room with a really quiet boiler. One happy chappy.

Just wanted to thank everyone here for their input. It was greatly appreciated.