Boiler Heat Exchanger

Golfmad25

Our Viessmann Vitodens W50 boiler was installed 7 years ago. Our service engineer has informed us that we need to replace the heat exchanger. This would be the third one. It is just three weeks out of the 7-year warranty. We suspect there is a design fault and have contacted the manufacturer who are refuting this and have indicated they will not replace it again. Has anyone experienced this issue?

WIAWSNB

Combi? If so, is this the main heat exchanger, or the secondary - or plate-to-plate - exchanger? 

For the former, summat seriously amiss. For the latter, sounds as tho' your system water has sludge in it.

Were you given any explanation? 

Golfmad25

It was the boiler plate heat exchanger that was replaced in February 2022. The boiler was serviced last Monday and magnetic filtration element showed little or no rubbish collected since the last service over 11 months ago. It is highly unlikely that sludge has caused this issue.

bjorn_toby_wilde

Our Worcester Bosch boiler is 21 years old and has never had anything major replaced. That sounds very suspect to me. Regardless of warranty period you should expect parts like that to last much longer.

WIAWSNB

Golfmad25 said:

It was the boiler plate heat exchanger that was replaced in February 2022. The boiler was serviced last Monday and magnetic filtration element showed little or no rubbish collected since the last service over 11 months ago. It is highly unlikely that sludge has caused this issue.

Thanks for the confirmation.
I'm afraid I can personally confirm that even small quantities of sludge can build up and cause a plate exchanger to block over a couple of years. And I suspect very much that this was the cause. Ie, not a 'fault' with the part.
Could you confirm the symptoms, please? I take it the part didn't leak in any sense (internally or externally)?
Did the DHW run cold after a short period of use? Did the delivery water temp fluctuate wildly, hot to cold and back?
Did the system pressure increase significantly at the time of the fault? (I'm assuming 'no')

WIAWSNB

What to do?
Assuming the symptoms do indicate a slow blockage of the plateX, and assuming your service engineer was also the Viessmann-approved installer, and assuming you had annual services in order to comply with the warranty terms, then I think you can safely conclude they didn't clean the system adequately at the time of installation.
In short - what other possible explanation could there be?
In which case, I think you'll have a valid claim against them. 
Do you have Legal Protection on your house insurance?

Golfmad25

Thanks for all the advice. 

plumb1_2

Remove it from the boiler and powerflush it.

Eldi_Dos

plumb1_2 said:

Remove it from the boiler and powerflush it.

Is there any chemical you could steep it in and rinse through if you do not have access to powerflush?

plumb1_2

Eldi_Dos said:

plumb1_2 said:

Remove it from the boiler and powerflush it.

Is there any chemical you could steep it in and rinse through if you do not have access to powerflush?

Not really as it’ll just sit there. I used to use sentinel X800  with a Kamco unit, with flow and reverse action. And connect a magnacleanse to it.
Happy passed on to young Plumb1 now, to much hard work doing powerflush in correctly.

WIAWSNB

Eldi_Dos said:

plumb1_2 said:

Remove it from the boiler and powerflush it.

Is there any chemical you could steep it in and rinse through if you do not have access to powerflush?

There are, but can't recall the best ones. The interweb has a lot of info.

P2P removed, drained, filled with the cleaner to the brim, and left. Then flushed through with a hose or pressure washer.

But, it's unlikely to be a thorough clean.

Latterly, I've bought 'reconditioned' exchangers on t'Bay - around £25, and literally as good as new. 

I think Golfmad has a case against the installer/service agent tho'. They should have sussed summat was amiss a while back.