Viessmann 222F banging

[Holgs]

Hello

I have had a new 222F with WC installed about 9 month ago and only recently noticed a banging. I seems that when the burner fires up all is ok and modulation (according to the VI app) is going from 60% to 9%. Once the burner turns off I can hear 3 banging noises in the pipework, bang followed by a bang bang noise. The system is operating ok but the noise wakes is up from time to time. I know the system only started doing this a month or so ago which is weird. Anyone seen such phenomenon before?

thanks upfront for any advice.

 

[ashtonc333]

I also have a Viessmann 222 and ever since installed have had a really loud bang from the boiler periodically which rattles through the pipework in the house. This turned out to be a faulty diverter valve which has been replaced a couple of times by Viessmann. It seems like an inherent manufacturing problem as it only last about 6-12 months before it goes again and was like this since first installation. Viessmann have said that the problem is due to a dirty water in the pipes, this was an assumption from the engineer. I had a plumber flush the full system as advised and he said that the water wasn't an issue, it didn't need flushing and was no different to 90% of UK houses. Viessmann seem to have a poor quality issue if their valves won't cope with standard UK water systems. The valve has just gone again and Viessmann have refused to honour the warranty as they say it's my problem. They said they will charge me around £120 for a call out and not fix the issue. I'm very sorry I had a Viessmann boiler installed, poor quality and terrible customer service.

 

[omph]

This post is for future end users looking for solutions to this problem (diverter banging/replacement).

Viessmann is a German made product and Germans have very high standards with regards to water purity/quality i.e. VDI 2035. Unfortunately, similar standards are only a recent thing in the UK and the UK industry is far behind.

The boilers are exceptional IF installed properly - This includes a full system power flush before installation - and that includes flushing the radiators individually too. The water needs to be clean - getting 80% out is not enough, it needs to be 98-99%. Most plumbers do a half baked job and this can cause issues. When powerflushing, make sure the plumber sets the diverter valve to mid-position - This means the boiler is not in heating-only or hot water-only, both "heating circuits" are accessible so the water can clean the system properly. This is usually done by setting the boiler into the "filling program" which is setting C.1. to ON in the commissioning assistant (page 33).

The second component is limescale. These boilers should NOT be filled with tap water, they must be filled with distilled or dimineralised water. The limescale build up and/or sludge can cause the diverter to "stick" hence the banging when switching from heating to hot water. Viessmann do sell rebranded Purotap filters for this: https://viessmanndirect.co.uk/Catalogue/Water-Treatment/Technical-Water/PUROTAP-micro

The limescale issue is both a blessing and curse. Limescale in general is not good for boilers as it can significantly reduce a boiler's efficiency by creating a thin insulating layer between the water and the heat exchanger.

The other great thing about using demineralised/distilled water is you do not need any inhibitor and the system shouldn't have any corrosion issues so sludge will not be a problem for the duration of the system's lifetime.

If you currently have diverter banging issues, get your system power flushed thoroughly, then replace the diverter valve and re-fill the system with dimineralised water.

There is a chance the boiler itself still has small amounts of gunk in it and in such cases, it will need to be cleaned out manually by removing the hydraulic block, and the exhanger. Viessmann will not cover this since the installation was done incorrectly and you will have to pocket it yourself.

If the system water is clean the valve will not stick and bang - if it does, that means the water still has impurities.

 

[Rageyboy91]

I have the same issue diverter valve breaks every 12 months. They originally designed the diverter with no filter, then they added a mesh filter to the new ones but it still breaks, obviously they have a serious problem with the quality.

 

[omph]

when you say breaks, what do you mean ?