Worcester Highflow 400 BF

My Worcester Highflow 400 BF was installed 6 years ago in our new house and has broken down at least twice every year, the most common expensive item which fails being the DHW Heat Exchanger at over £200 to be replaced!
After the fourth time of having this replaced (the system has been charged with inhibitor each time) I have decided to replace the part myself as I am back to the boiler tripping out every time hot water is drawn off as the exchanger makes a 'kettling noise'.
Looking at the servicing instructions left with the boiler it seems you almost need to completely strip the boiler down, removing the diverter, the pump, the manifolds etc, which would take a considerable amount of time. After taking all the panels off the boiler it seems to me I should be able to remove the exchanger by removing four screws on the support bracket and one screw in the centre of the bottom manifold and easing the exchanger back off the o-ring seals, probably taking about ten minutes!!
My question is - am I missing something here, especially when in the past most heating engineers go white when I mention replacing it? Bearing in mind the boiler is floor mounted in the garage and I have access all round it. Surely it can't be that easy? Any comments from the professionals please.

Jimmyg

I have decided to replace the part myself

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You will regret it.

If you have had 4 in 6 years then maybe you have an underlying fault.

Its no good just adding loads of inhibitor to the system.

It needs cleaning out properly.

If the plate heat exchanger could be removed by undoing 4 screws don't you think worcester would have put that in the manual?

probably taking about ten minutes

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Instructions are written given minimum access to the boiler (Highflow - in effect only from the front).
If you can get in at the side AND remove all the fixings without harm AND there's room to get the HX off backwards - and then be able to refit it - all well and good.

No, it's not that easy. I've seen it done were the top manifold was left in place and the rest of the hydraulic assy removed...but that doesn't count cos it leaked afterwards!! I've done literaraly hundreds of them there 400 plates (I'm an ex WB engineer) and I still think the best way, is to remove all the hyd assy as per manual. That way you can clean it all thouroughly. I used to quite enjoy em actually...couple of cup's of tea...and just taking my time and using plenty of Molykote grease.
However, before doing all that you might want to check the primary filter because it might just be that this is partially blocked. This is situated in the top manifold. Remove PRV, stat out the pocket, then indo the screw and clamp holding the brass pocket in to the manifold. withdraw the pocket and there SHOULD be a filter inside.

Many thanks to all of you for the replies:

Scatmanjohn -

You will regret it.

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You could be right, I may well regret it, but without sounding boastful I do consider myself a competent DIYer having rewired houses (can't do that anymore without Part 4), fitted kitchens, bathrooms, showers, did most of the labouring when building my own house and used to earn extra money repairing cars for friends. It's not about doing a tradesman out of a job it's more about the challenge and the pride.

If you have had 4 in 6 years then maybe you have an underlying fault.

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Could be right about the underlying fault and I am contemplating calling in a BW engineer.

Its no good just adding loads of inhibitor to the system.

It needs cleaning out properly.

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I don't believe any was added when the system was first commissioned which may have contributed to the problem, we are in a hard water area, and the only inhibitor added after that is after each drain down. Heating Engineer friend doesn't think a powerflusher would work here as getting the fluid round the heating circuit is not that easy with this boiler??

Jiminblack-

you might want to check the primary filter

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thanks for the tip about the filter will try that first. Believe me I don't have anything aginst BW or their engineers, cos I have a second wall mounted Worcester 24i boiler which has run like a Swiss clock from day one (the original heating engineer said we needed two separate boilers on separate circuits to cope with the number of rads and bathroms - it's a big house).

I used to quite enjoy em actually...couple of cup's of tea...and just taking my time and using plenty of Molykote grease.

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I can make you as many cups of tea and bacon butties as you like if you are feeling bored or at a loose end!!

The last BW engineer replaced the part in about 40 minutes which means either he did it the way I am suggesting or he was trained by Formula One pit stop mechanics!!

Croydoncorgi-

Instructions are written given minimum access to the boiler

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That's what I was wondering, that these instructions apply more to units fitted in cupboards in kitchens, utility rooms etc where space is almost none existent.

One final salutory point about over-engineering and lots of instructions - NASA spent billions of taxpayers dollars developing a pen to go into outer space that would work upside down, in weighlessness, in very harsh conditions, never skip or blob and last for ages - the Russian just took pencils!

Thanks for your all help guys will make a decision today - too much earache from indoors about cold water!

Cheers

jimmyg

Jiminblack - do you mean the filter that sits in the waterfilter housing between the mains cold water inlet valve and the flow switch body?

No, it's in the top white manifold were the temperature phials sit.

jiminblack -

No, it's in the top white manifold were the temperature phials sit.

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Thanks for the info, will try that first and let you know how I get on.

Cheers
Jimmyg

jiminblack

No, it's in the top white manifold were the temperature phials sit.

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Gave up in the end and called out WB. Very efficient came out the next day and it took him two and half hours to replace the exchanger (with lots of molykote! and he made it look so easy) plus he also replaced both the manifolds - and no there was no filter in the top manifold. It was completely blocked up with crud.
Cost me £245 for the repair so he recommended isolating the boiler, removing a rad, connecting a power flusher, running the chemicals through the system and then refilling with inhibitor - otherwise he reckons he will be back in less than a year.

What do you think about the flusher?

Cheers
Jimmyg

YES GET IT FLUSHED.

and maybe bang a magna clean on it.

Unfortunately, this is a very typical example of a DIYer thinking that just adding inhibitor is all thats needed. It is, but only if the system is shining clean.

Yet again the original installer did not power flush the system to get rid of dirt and the user had had problems with dirt twice a year.

Thats not the boiler's fault its the installer's. I understand the likely senario! He wants the work and knows that if he quotes for properly cleaning the system he will not get the job. So he joins the cowboys and quotes a price without power flushing and gets the job but the customer suffers for the rest of the boiler's life.

Tony Glazier

Jimmyg said:

My Worcester Highflow 400 BF was installed 6 years ago in our new house

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Do you mean brand new house or new to you? If brand new then non barrier plastic was used. You need it fully repiped.

If new to you, as stated cleanse the system and fit magnetic filter without fail.

If it is an estate of these things newbuild 6 years ago, allert the neighbours to take evasive action also.

Worst case scenario some of them will already have been sold new boilers but still underlying problem not addressed and no magnetic filter fitted in the plumbers' lack of conscience and profiteering intentions.

Thanks to all for the comments/advice.

Unfortunately, this is a very typical example of a DIYer thinking that just adding inhibitor is all thats needed. It is, but only if the system is shining clean.

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Agile - take exception to this comment, I realise it is not just a matter of slinging in more inhibitor - by the way that advice came from a Corgi registered heating engineer - so much for professionalism!

The house was brand new so all the fittings were new, and it was a one off we designed ourselves with an architect. We had some superb craftsmen work for us, but we also had some complete dorks who were very quickly found out and shown off the site. Unfortunately when we were not around we had to rely on the craftsmen to do the job properly and I think you are right he never flushed the system out properly.

I realise now that the original installer was an old guy who was probably on the limit of his knowledge with modern systems - he was more of a rag and solder man I think.

Off to hire a flusher - by the time I have finished you will be able to drink the water coming out of the system Oh - and off to buy a Magnaclean.

Once again thanks for all your input - all very useful info.
Cheers

Jimmyg

What I don't understand is how you got all this magnetight into a new system unless it's piped in non barrier plastic, and if it is you should repipe it in copper or barrier plastic in that order of preference.

Paul

What I don't understand is how you got all this magnetight into a new system unless it's piped in non barrier plastic, and if it is you should repipe it in copper or barrier plastic in that order of preference.

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Watching the plumber who installed the system he used 10mm pipe sheathed in a plastic coating, because he said we needed this as the ground floor was concrete flooring. I did ask him to box all the piping in wooden shuttering in case of a leak or we needed to replace any of it - even bought the wood - then found once the concrete had been poured that he had only boxed in where there were any joints!

Thanks for the advice but don't think her indoors would be pleased with the prospect of ripping up all that concrete to get at the pipes - that's assuming I can follow where they were laid!!

The other point is that we do live in a very hard water area - so on the advice of a heating engineer I fitted an electronic water descaler on the incoming mains - one where you wrap the wire around the pipe - not sure it's doing any good.

Cheers

jimmyg