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Discuss Power flush before blocked heat exchanger renewal ? in the Plumbing Forum | Plumbing Advice area at PlumbersForums.net

Graham Humber

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5
Evening All

We are having a new heat exchanger fitted to a Veissmann boiler, the boiler is only six months old, the installers carried out a power flush but only after the boiler had been running for about a fortnight, then after six months it failed to heat radiators to temperature. Viessmann came out identified the problem as a blocked heat exchanger supplied by Viessmann as a good will gesture. Should the installers power flush the system before fitting the new heat exchanger ? I don't think the first power flush which cost us £600 cleared the system properly
 

scott_d

Plumber
Gas Engineer
Messages
5,963
Is it a one pipe system?
Do you have a magnetic filter filter?
 

gmartine

Esteemed
Gas Engineer
Messages
1,784
That's really not good, were they approved installers? Viessmann are rather hot on their water quality so that really was a gesture of goodwill on their behalf as the system should've been cleaned just prior to the boiler being installed or included as part of the installation.
 

Graham Humber

Messages
5
That's really not good, were they approved installers? Viessmann are rather hot on their water quality so that really was a gesture of goodwill on their behalf as the system should've been cleaned just prior to the boiler being installed or included as part of the installation.
They are approved installers but they haven't covered themselves in glory, multiple visits by different engineers. Started by leaving it as an open vented system, got it running for a couple of weeks then it failed, told us we would have to go to a closed system. Cut off our solid fuel range which was on the system, because they had no idea how to get the two systems working in conjunction. We had to engage another independent Heating Engineer to separate the solid fuel from the gas system with the only integrated part being a twin coil tank - Gas is now closed system, Solid fuel vented system, this extra work has been at additional cost to us. The worry now is they are saying the system doesn't need flushing before fitting the new heat exchanger, common sense says there must be debris/sludge in the system otherwise it wouldn't have blocked in the first place. removing the heat exchanger will only remove what in it not any residue in the system.
 

ShaunCorbs

Staff member
S. Mod
Plumber
Gas Engineer
Messages
30,322
Solutions
1
They are approved installers but they haven't covered themselves in glory, multiple visits by different engineers. Started by leaving it as an open vented system, got it running for a couple of weeks then it failed, told us we would have to go to a closed system. Cut off our solid fuel range which was on the system, because they had no idea how to get the two systems working in conjunction. We had to engage another independent Heating Engineer to separate the solid fuel from the gas system with the only integrated part being a twin coil tank - Gas is now closed system, Solid fuel vented system, this extra work has been at additional cost to us. The worry now is they are saying the system doesn't need flushing before fitting the new heat exchanger, common sense says there must be debris/sludge in the system otherwise it wouldn't have blocked in the first place. removing the heat exchanger will only remove what in it not any residue in the system.

get it in writing and make the md sign it saying they will warranty it if it fails due to system / water quality and there liable for all costs
 

king of pipes

Esteemed
Plumber
Gas Engineer
Messages
5,551
As above theres a case for hydraulic seperation here ? but a through cleaning of the system chemically and then using the appropriate method to remove a high percentage of the debris should protect the new heat exchanger, using a dirt seperator mag filter and inhibitor will add further protection and keep the boiler manufacturer happy . Kop
 

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Graham Humber

Messages
5
Do you know why it wasn’t flushed straight away?
They only allowed for a chemical flush in the initial install, power flush was done after about a fortnight of them messing around trying to get the system to flow. Power flush was done when they change it from the original open vent system to closed system to get the flow so they said. Previous oil boiler although old and in need of replacing was still able to get flow round the system fine
 

king of pipes

Esteemed
Plumber
Gas Engineer
Messages
5,551
The damage was done in that 2 week window in my opinion ,open vented systems can be notoriously dirty add in the fact it was a oil boiler then converted to gas more protection and care was need. Kop
 

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