Vaillant Primary Heat Exchangers & Blockages

[Plumb Logic Ltd]

Are any other Gas/Heating engineers having problems with blocked primary heat exchangers on Vaillant boilers, even on new installations that have been chemically flushed and have filters/dirt seperators protecting the new boiler/s ?

We are prodominantly a mechanical installation company specializing in large domestic new builds that require light commercial plumbing and heating installations.
The specifications for these developments regularly require us to install pairs of Vaillant Ecotec 46 or 65 commercial boilers or Vaillant Ecotec 637 domestic system boilers as part of a sealed, pressurised system.
The boilers are installed in a designated plant room where we also install a bespoke low loss header allowing us to seperate each heating cicuit (UFH, Radiators, Towel Rails, HW)
As each heating circuit is installed, we carry out a full chemical power flush on that individual circuit, so we know that the system is being flushed thouroughly. The newly installed radiators and towel rails are included in this flush.
We install a magnetic filtration device on each return pipe between the boilers and low loss header.
The system is then correctly dosed with the required Sentinel products before the boilers are switched on and the system is tested and commissioned.

So...In a new build development, with a brand new central heating system that has been flushed to remove installation deposits, fluxes etc. and magnetic filtration devices installed protecting the boilers...we are STILL getting blocked heat exchangers on some of our jobs, approx. 2yrs after the boilers are installed.

Is there a fundemental problem with the Vaillant heat exchangers ?
Do other boiler manufactures have better designed heat exchangers ?

 

[chris watkins]

We have had one or two as you described. What is the fault code ? How are Vaillant responding? they were not to helpful on site claiming it was the U/F & some other twaddle.
I do know someone who can clean the heat exchangers, if you need.

 

[rsr]

Are you in a hard water area and if so are you using limescale protection?

 

[stevetheplumber]

when i was at vailants for training they did stress the importance of removing certain flushing chemicals from the systems before they were run ive always found vailants to be quite good if you are having ongoing problems but like all big organisations it will depend who you speak to

 

[FD Powerflow]

This is second hand info so take from it what you will but Sentinel X100 contains phosphate, this naturally combines with Calcium Carbonate (hard water) and becomes Calcium Phosphate, (almost bone like in appearance). This forms primarily on the primary heat exchanger and shows itself as scale in the shape of the coil of the heat exchanger. Its definitely NOT only Vaillant suffering. I heard the Sentinel issue from the SIME rep, they now only recommend Fernox F1 as it doesnt contain phosphate. Only real cure is to dissolve the scale using DS40 or FX2 and then protect with F1. Check the SIME boiler manual online and it explains the above.

 

[Roger Welton]

Interesting info.

 

[chris watkins]

OK, but if filled once or twice how much can form ? would it effect the boiler in this way ?

 

[gassafe]

This is second hand info so take from it what you will but Sentinel X100 contains phosphate, this naturally combines with Calcium Carbonate (hard water) and becomes Calcium Phosphate, (almost bone like in appearance). This forms primarily on the primary heat exchanger and shows itself as scale in the shape of the coil of the heat exchanger. Its definitely NOT only Vaillant suffering. I heard the Sentinel issue from the SIME rep, they now only recommend Fernox F1 as it doesnt contain phosphate. Only real cure is to dissolve the scale using DS40 or FX2 and then protect with F1. Check the SIME boiler manual online and it explains the above.

interesting to see if vaillant stop recommending Sentinel for this reason!

I always thought sentinel were the best products available so if interesting if its true!

 

[Plumb Logic Ltd]

If the boiler gives a fault code it is usually F75, but generally the boilers just become noisey (banging) and they won't heat the water to the required temp or go into full burn. We usually try to put the boilers into "Chimney Sweep" mode as a test, and if the boiler doesn't respond it is a good indication that the heat exchangers are blocked.
Vaillant have stood firm and said that the boilers don't have any blockages in the water ways of the heat exchanger when the boiler comes out of the box, so it must be a system issue and they are not prepared to do anymore than that. It is very frustrating because as I mentioned in my post, we have done everything that we can to install and protect the boilers in the best possible way and feel that we are now being left stranded to sort out the situation.

 

[Plumb Logic Ltd]

Are you in a hard water area and if so are you using limescale protection?

Yes we are in a hard water area but I have spoken to the rep from "Sentinel" who has said that this shouldn't matter as long as the water is correctly dosed with chemicals ?