Vitodens 100 central heating stuck on

[Wile]

I've searched for anything like this problem, both on the web in general and here at DIYnot in particular, without anything near it.
I noticed when I woke up this morning, that I could here the whisper of the central heating . When I checked the Honeywell controller it was still set to manual (which is how I use it) and 18 degrees (which equals off above that temperature) and the ambient was 21.5 but the heating was still on.
I’ve tried everything in descending order from fitting new batteries to the controller, turning down the temperature on the heating side of the boiler, switching the controller to off, until I have now turned the boiler heating control to the off position but the heating still comes on!!!

Although our boiler man has a call-centre answering system, as this isn’t in the same league as the previous problems – water leaking from the boiler pipework (the last problem), the boiler shutting down in the cold snap last winter (condensate pipe frozen, which we controlled with pouring boiling water over it), heat exchanger passing and, of course, our old friend the sticking flap valve, I’ll leave him to his Sunday and call him tomorrow.

Unless, of course anyone out there has an answer – if not, I’ll post the outcome here for all to see (and find).

When I was looking for a new boiler in 2006 this one came out tops and I have been having the “you said this was the Rolls-Royce of boilers” thrown at me by “The Management” ever since . All-in-all I think I made the right choice then and would seriously think of having another one if we moved.

Another hour or two of searching and the predicted Rolls-Royce of boilers dig when she got in from relly visiting and I've found a hijacked post here //www.diynot.com/forums/viewtopic.php?t=234831&start=0 on DIYnot which suggests a diverter valve problem?
Would that mean the heating side would only get fed while the water side was in use?

 

[D_Hailsham]

I've found a hijacked post here //www.diynot.com/forums/viewtopic.php?t=234831&start=0 on DIYnot which suggests a diverter valve problem?
Would that mean the heating side would only get fed while the water side was in use?

Only combi boilers have a diverter valve.

As a combi boiler only runs for hot water when a hot tap is opened and you say that you could hear the heating going when you woke up (i.e before any hot water had been drawn), I would assume that you do not have a combi boiler.

This means that there is probably a fault in a motorized valve. You will either have one (left pic) or two (right pic).

View media item 5946View media item 11762

 

[looneyfitter]

Could also be a stuck relay in the honeywell controller your using. What lights are on- on the front of the boiler\?

 

[Wile]

Thanks for your time.

It is a combi which is what puzzled me about first thing this morning as, as you say, no hot water was being drawn. What led me to think it might be similar to the hijacked thread was that "The management" had a shower when she came in from the gym and the heating came on.
But no hot water is being drawn now, and the system is running.

As to the boiler itself, no warning light is showing, only a temperature reading a the tap symbol now.

 

[looneyfitter]

Hard to say without being there mate. is the boiler running now? Nit had a propper look in the 40-50 ive fitted, but HW flow switch possibly.

 

[Wile]

Got hold of "The man" who took me through a reset procedure - don't ask, I've no idea - which, hopefully, has reset something. I'll let you know.

 

[Agile]

Its always nice for us to know exactly what any problem is.

Any one engineer only sees his own portfolio of repairs and hearing of other less common problems widens the experience.

Tony

 

[mysteryman]

It could be a stuck diverter valve and the boiler either in comfort [hot water preheat] or the domestic flowswitch also stuck on. The condensate pipe needs re-routing - it should not be installed so that it can freeze.

Ring Technical in the morning!

 

[Agile]

I dont see how any telephone instructed reset could unstick a diverter valve or a DHW flow switch from outside the boiler casing!

I like to get into these old boilers!

 

[looneyfitter]

So the reset worked then?

 

[Wile]

The "reset" seems to have done the trick.
The procedure was the same as in the installation manual of heating control fully clockwise then back in less than 2 seconds causing the display to show SERV.

As for the condensate pipe:-
The house is circa 1957 so when the previous owners had CH fitted they used the cupboard under the stairs to site the boiler. When we had the new boiler fitted, instead of the condensate pipe dropping to just above ground level, it was run to the drain which is a couple of metres away.
Last winter being exceptional the freezing problem has not occurred before and once we knew what to do, the occasional kettle of hot water was no hardship.

 

[looneyfitter]

External condensate pipework or pipework which is likely to freeze, should be either lagged or a minimum of 35mm in diameter.

 

[mysteryman]

It should still be lagged with the discharge beneath the water surface in a back inlet gully or a soakaway. Otherwise it will freeze from the outlet and still back up.