Vokera compact 24 heat exchanger gone - again

sandshoeharry · 17 Jan 2011

Less than a year after having this new boiler fitted the pressure rose, water started discharging on to the roof via the overflow pipe and then the system shut down. The engineer came and said the heat exchanger had gone so water from one part of the system was going into the other and causing the relief valve to pump it out on to the roof . Result new heat exchanger fitted.

Now about 12 months or so later the same sequence of events and again the boiler has stopped - if I turn off the mains supply the central heating works but no hot water at all.

I have 3 questions:

1.This seems to be an inherent fault does anyone know if Vokera have done anything to upgrade the part to avoid inconvenience/ expense for users.

2.As the heat exchanger has already been replaced under warranty I assume as the replacement has now gone the warranty period on it will run not from the time the boiler was bought but from the time the replacement part was fitted is this a correct assumption.

3.I read somewhere that the heat exchanger on this boiler was very easy to fit . I've got some limited plumbing experience eg fitted my own bathroom ie toilet, bath, sink and removed and fitted radiators is replacing the exchanger something I could do and if so can anyone post or point me to step by step instructions.

Oh one last question is there a Vokera users group I couldn't find one.

DP · 17 Jan 2011

Vokera users group is here and in combustion chamber.

sandshoeharry · 17 Jan 2011

DP said:
Vokera users group is here and in combustion chamber.

Thanks, where do I find combustion chamber you refer to

muggles · 17 Jan 2011

1) Not sure whether they have been upgraded to be honest, but you're right that there is a bit of an issue with them.

2) You are incorrect I'm afraid, the warranty is from the time the boiler was registered and not from the time the replacement part was fitted, unless the manufacturer specifically states otherwise.

3) It may well be but you need to break into the combustion chamber to do it, meaning you need to be competent in gas work. As we don't give advice on gas-related work on this forum beyond telling you to get a registered gas installer in, I can't give you instructions on how to do it. It's in the manual though if you really feel like taking the risk.

Ray84 · 18 Jan 2011

i wouldnt advise replacing it yourself due to the safety side of it, especially when you total the cost of the part itself labour wont be too much more expensive.
Its a compact ive got, came new when i moved into my house, i always thought when that goes ill swap it for another boiler as its bound to be either that or the pcb which will fail first and are quite pricey but i suppose thats how vokera make their money.
Id thought about putting a pressure reducing valve onto my mains comming in to reduce the pressure accross the house in the hope it might prevent possible damage but as yet havent bothered.

Ray

Agile · 18 Jan 2011

Vokera are the only boiler which seem to have problems with heat exchangers leaking so often!

Its just a wrong day for me as I wasted a lot of time today trying to help somebody who was not very grateful for my help with a Vokera boiler with a leaking heat exchanger.

Tony

BingoBongo · 20 Jan 2011

have seen many of these go,advise is to fit a pressure reducing valve and mini expansion vessel

sandshoeharry · 20 Jan 2011

Thanks to everyone for the replies.

The answer seems to be that I will have to get a Pressure Relief Valve fitted on the Domestic Hot Water input side in order to help ensure that another fragile heat exchanger doesn't go - have to say I won't be buying Vokera gain.

New Heat Exchanger required of course as well so facing a biggish bill hence my feelings towards Vokera. I do hope they don't make microlite or helicopter engines frankly it amazes me that in this day and age anyone should be making a unit with so few moving parts that seems to fail so often.

Am going to have a look and see if there are any Japanese manufactured boilers on the UK market - my experience with cars is that components hardly ever fail and the standard of their manufacturing sadly seems to be much higher than what we Europeans can produce . It pains me to say that because my son works for a UK manufacturer as a design engineer.

Ray84 · 21 Jan 2011

I understand what you mean its quite upsetting that they seem to be built so poorly(though i suppose it keeps us in a job)
Yesterday i had one that needed an ignition PCB. boiler was moved a few months ago leaving 2 leaking valves. The fans squeeling like mad and i suspect the expansion vessels nacked though didnt bother checking.
Basicly i wasnt sure to advise repair or replace and for a boiler thats 3 years old you'd be right to expect it to be in better shape.
Anyway guy wants it fixed (good for me) but im half expecting a phone call a few months down the line with your problem, bit of a headache!
Ray

arundel gas services · 31 Jan 2014

usually due to high water pressure in the main fit a pressure refusing valve at 3 bar and you will have no more problems

kevkdg · 24 Dec 2021

Apologies to bump this thread, but I am on my third heat exchanger since 2018.

The original one with the Vokera Compact 24 boiler lasted 13 years and then failed (separation between mains water for hot water and heating side was breached causing pressure to rise and PRV to activate).

So, replacement fitted in 2018 which failed in 2020. So another replacement fitted in 2020 which failed last week. Have now been advised to fit a Pressure Reducing Valve. Boiler instructions says max of 6 bar though for the hot water feed, so was wondering whether mains water pressure often exceeds this and why the original heat exchanger lasted 13 years under the same conditions that two replacement ones failed within 18 to 24 months each?

Will a pressure reducing valve affect my shower experience?

Can I simply fit this just before the hot water feed into the boiler. Looks easy enough as pushfit:

Reliance Valves Predator Compact 312 PRV 15mm x 15mm | Pressure Reducing Valves | Screwfix.com

Thanks

DP · 24 Dec 2021

Do you have a water meter? If yes, do you have a mini expansion vessel fitted to cold water pipe to the boiler.

kevkdg · 24 Dec 2021

DP said:
Do you have a water meter? If yes, do you have a mini expansion vessel fitted to cold water pipe to the boiler.

Hi, yes we have a water meter. No visible sign of a mini expansion vessel on cold feed to DHW. I know the boiler has an internal one for the central heating as the engineer re-pressurised it.

DP · 24 Dec 2021

It is a requirement that a mini vessel be fitted on the cold inlet if there is a pressure reducing valve or a water meter fitted. Water that passes through these components are locked in the pipes to the taps. Combi heats the water for the tap, tap is closed and residual heat continues to heat water in the boiler and pressure rises in the hot water loop.

Boilers like Vokera Flowmatic, RS Turbo, Vaillant Sine 18 and VCW compacpacts were already fitted with min vessel. Some later boilers had option to instal one, Some MI ( do not know if all ask for thus as I do very little installation work) as for a mini vessel to be fitted if there is a water meter or PRV fitted.

It is not the quality of the heat exchanger in your boiler but lack of essential component that is leeding to heat exchanger failure

Gasguru · 24 Dec 2021

+1
Maybe you didn't have a water meter with the original heat exchanger.

Consider the domestic water temperature perhaps set a little lower on the boiler and the heating is turned on.
The water sitting in the domestic loop inside the heat exchanger might reach 85 degrees and the subsequent expansion can rocket the pressure up within the domestic pipework.

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Vokera compact 24 heat exchanger gone - again

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