Viessmann boiler failure

[ppppenguin]

Both Mark Hennessy and I are fond of claiming that Viessmann boilers are the best in the business. Mine has gone horribly wrong this morning.

I can downstairs at about 0630 this morning, house was nice and warm but then I heard some strange noises from the kitchen. At first I thought it was electrical arcing but then saw water dripping from the ceiling, just below where the boiler and airing cupboard are on the 1st floor.

Rush upstairs and find lots of water dripping from the bottom of the boiler. Switch off system, get boiler's documents, stored under the boiler out of the way. They're not too wet. Find I've got extended warrany until November this year. Don't yet know what this means.

Take case off boiler and find that flexible pipe that carries the flow from the main burner assembly has split.

Mop up as much as possible, get stuff in kitchen out of harms way.

Will phone Viessmann as soon as they open. If I can get the part from their local agent I'll probably just fit it myslef. hope there isn't any collateral damage. The electronics are well protected and seem to have stayed dry.

PS: Just phoned them and got a human being out of hours! Unfortuantely they can only take messages so i'll ring back at 0900 when they open. the out of hours person said they should be able to get somebody to me today.

[Radio Fixer]

Tough Jeffrey. But similar for me, a tap connector after 30 years has started to leak. Its hard to get at as well so that's my day sorted out. And doesn't even a tiny amount of water make a mess. Mine is upstairs with chipboard flooring which takes ages to dry out.

Gary

[Murphyv310]

HI.
Condensate drain on boiler has split. Common fault on just about every condensing boiler.
Mine did the very same on Christmas day, I made a temporary repair and all was well till the correct pipe was fitted.
It's a 10 year old Glow-worm.

[Mark Hennessy]

It's not the condensate pipe, Trevor, it's a pipe carrying the flow...

I've got the Vitodens 200, which is different to Jeffrey's 100, but I think I also have a flexible pipe in the same role. Will have to keep an eye on it. It wouldn't have rung any particular alarm bells with me as after all, car hoses are rubber, and they endure much higher temperatures than a domestic boiler.

Good job the boiler was upstairs, so the quantity of escaping water would have been minimised (unless you have a loft room or something?). Mine is the highest part of my system. Though how long would it have taken to realise something was wrong and turn the pump off? With mine, I've never worked out if the pressure gauge is linked in to the control electronics, but I'd hope it was. There isn't a separate low pressure sensor IIRC.

Mine has been in for nearly 5 years now, running 16 hours per day. So far, so good. I'll probably regret saying that now

[Radio Fixer]

Why not change the connector sometime Mark before it goes? 

Gary

[Yorkie]

Don't know if yours is a sealed system combi boiler (as opposed to an open vented) condensing boiler. If so, is it the metallic flexible filler loop hose, which is under mains pressure up to the re-pressurising filler tap, which you need to periodically turn on to re-pressurise the system then turn off when the dial indicates the correct pressure has been attained? It's unusual for then to fracture, but they're commonplace and the likes of Plumb Centre will have them and a simple task to replace. I'm puzzled when you say 'its coupled to the main burner' - the only think that goes to the burner is gas - not water. If the re-pressurising  pipe bursts, it doesn't stop the boiler from operating normally provided the re-pressurising valve isn't opened.  

Mains water pressure varies, but generally is about 75 PSI or in 'new money' 5 Bar. I would imagine that the test pressure of such hoses is at least double that. Most combi boilers operate on 1 - 1.5Bar and most pressurised systems leak slightly over time due to minute leaks on radiator valve,  and if the system pressure drops much below  1 Bar, the boiler will shut down.

There's a pic of a filler loop hose at this link:

https://www.youtube.com/watch?v=rr6k8eBqoOg


This video is a bit shouty, but useful:

https://www.youtube.com/watch?v=4meZgMAUecw&ebc=ANyPxKr_IPP-L3z2abA-I-PFYrYiTDNBYA80I7ogX0ewyPGqCqk5dl5dxHLxmVKQol1fLn64817L

Good luck with sorting it out!

[ppppenguin]

"Don't know if yours is a sealed system combi boiler (as opposed to an open vented) condensing boiler. ..."

There's a common confusion here.

All modern boilers are condensing, whether combi or otherwise. All combi systems are sealed and pressurised. Other systems can be pressurised or with header tank, depending on how you wish to design the system. It's recommended to pressurise a new system as it gives cleaner water conditions. No area of water exposed to air in the header tank. Also if, like me, you have a loft conversion, getting the header tank high enough isn't easy. I managed it on the original installation but it was a pretty fine margin between working OK and overpumping into the header tank. That was a very good reason to change to pressurised when I changed the boiler.

When I fitted my boiler in 2011 I changed the system from header tank to pressurised. I bought a so-called system boiler which has all the necessary bits built in. Pump, pressure gauge, bypass, expansion vessel etc. Except for the filler loop which I had to buy separately and fit externally. I'm glad I did pressurise it, as a system with header tank has an unlimited amount of water available. Mind you, a system with header tnak runs at much lower pressure so the hose might not have split in the first place.

The part that has failed on my system is item 002 on p94 of this document. It connects the primary flow from the main combustion unit to the rest of the water system.

http://www.viessmann-us.com/content/dam/...1bc_is.pdf

It looks like a bit of rather thin car radiator hose. IMHO it's not up to the job and should be replaced by something with a flexible metal jacket. Just like the hose used to connect the expansion vessel to the rest of the system.

I pressurise my system to 1 bar when cold. It goes up to about 2 bar when hot. The overpressure valve should open at about 3 bar.

[Mark Hennessy]

Why not change the connector sometime Mark before it goes? 

Gary

To be honest, I've no reason to think these are a weak point - it's the first instance I've heard of, and it's probably a random failure. And mine is different to Jeffrey's.

Don't know if yours is a sealed system combi boiler (as opposed to an open vented) condensing boiler. If so, is it the metallic flexible filler loop hose, which is under mains pressure up to the re-pressurising filler tap, which you need to periodically turn on to re-pressurise the system then turn off when the dial indicates the correct pressure has been attained? It's unusual for then to fracture, but they're commonplace and the likes of Plumb Centre will have them and a simple task to replace. I'm puzzled when you say 'its coupled to the main burner' - the only think that goes to the burner is gas - not water. If the re-pressurising  pipe bursts, it doesn't stop the boiler from operating normally provided the re-pressurising valve isn't opened.

He's not talking about the filling loop hose...

The "main burner assembly" includes the heat exchanger, and one of the water pipes is rubber.

I've just dug out some photos of mine, which is different to Jeffrey's, and I have a copper pipe leading from the heat exchanger. I can't see what brings in the return as that is behind and comes from the pump/diverter valve assembly. The condensate collection pipe is rubber, but that's not what Jeffrey is talking about...

The heat exchanger on these is a lovely stainless-steel affair - a rectangular tube section that is coiled up leaving minimal gaps between layers to ensure maximum contact with the flame. I really can't understand why manufacturers continue to use aluminium, which is eaten away by the acidic condensate...

Note also how the expansion vessel is at the side, and is easy to change (just two screws from above, and unclipping the hose). Most boilers hide these behind the heat exchanger and require a major strip-down to get at - which is why most just add an external expansion vessel rather than replacing the failed one...

All the best,

Mark

[Mark Hennessy]

I pressurise my system to 1 bar when cold. It goes up to about 2 bar when hot. The overpressure valve should open at about 3 bar.

Mine hardly changes from hot to cold. Perhaps a quarter of a bar at most.

With my previous system - also sealed - the only time I got big hot/cold swings was when the diaphragm in the expansion vessel failed.

I wonder if the expansion vessel needs to be re-pressured?

[ppppenguin]

Mine has always had a big swing between cold and hot.  I've got quite a large house with lots of rads and I think the expansion vessel is only just about big enough for the system.

Mark, your boiler has a nice solid bit of copper for the flow from the main burner assembly. Rather better than a hose. The return to the main burner is a hose too on mine. The hose is probably quieter than the copper pipe as it will damp vibrations from the burner. Though the main source of noise is the fan.