Still got boiler problems

Since just before Xmas I've had an intermittent problem with my Viessmann Vitodens 200 system boiler. Basically, after heating the water cylinder at switch on it then trips when switching over to heating the house. A re-set sorts things. Most inconvenient as you wake up to a cold house. Doesn't happen every day, though. But more often than not. Can happen if you run off a lot of hot water like say for a bath, but less often than not.

The Viessmann engineer called twice under warranty and on the second visit (last Friday) replaced the main board with one which has later software. Saturday it worked fine - today back to its old tricks. The stored fault code he reckoned was a red herring (something to do with the burner).

I'll phone Viessmann technical who are very helpful on Monday and get the engineer in again - but anyone got any guesses as to a likely cause?

Reply to
Dave Plowman (News)
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"Dave Plowman (News)" wrote

Hot water cylinder thermostat not switching properly and allowing residual current through?

Reply to
Davey

What sort of plan is the system? Just wondering if there's some point where there's no flow path and the boiler is still firing.

Reply to
Andrew Gabriel

Doesn't use a thermostat - just a solid state sensor. Same as the room and outside one in principle. It measures ok and the display is giving the actual water temp just fine. They are usually pretty reliable devices - at least for several years. They're the same sort of thing as used to measure the coolant temp in your car for the engine management.

Reply to
Dave Plowman (News)

"Dave Plowman (News)" wrote

So its a thermistor then. It doesn't mean it isn't leaky though. Ask any Glow-Worm micron owner how reliable the thermistor has been in their boiler.

I would measure the voltage across the device when it's calling for heat for hot water, again when the demand has been met due to reaching temperature, and then once more after a system reset with just the heating calling for heat and compare. Could be nothing, but it's a good place to start, no?

If the mainboard has been changed, it's something auxiliary to it, so what's left? Heating 'stat (thermistor), hot water 'stat, diverter valve, what else? Bad earth?

Reply to
Davey

Glow-Worm micron owner how reliable the thermistor has

Of course it's "leaky", thats how thermistors work.

Reply to
Graham.

That could make your eyes water... ;-)

Reply to
John Rumm

If the sensor was faulty, wouldn't the temp readout be wrong? (you can call up all the various temperatures on the programmer. Inside, outside, boiler, hot water, etc.

I simply measured its resistance at cold and hot. Agreed with what I'd expect - although I don't have the actual figures for this one, only car ones.

The programmer has a second microprocessor which talks to the main one. I also have a zone programmer in the kitchen which talks to them both. Although that doesn't control the hot water - apart from switching it on or off.

Reply to
Dave Plowman (News)

;-) Guess he must be a plumber. Wouldn't suit them as there's more than just an on/off switch.

Reply to
Dave Plowman (News)

Some of the new WB models do not even have an on/off switch:-)

Adam

Reply to
ARWadsworth

"ARWadsworth" wrote

The only trouble free boiler currently in manufacture. One that you can't turn on in the first place :)

Phil

Reply to
TheScullster

Same as Rangers then. Or Celtic.

Reply to
Phil

I told this plantpot not to buy one of these boilers. I hope It breaks down every month now.

Reply to
Doctor Drivel

This plonker has a *very* short memory. They were his flavour of the month once as Google would easily show. However, I didn't let his 'recommendation' put me off buying a good product.

Do us all a favour dribble and go back to playing with yourself until the next election.

Reply to
Dave Plowman (News)

I told you not to buy THAT model!!!! A told you want to do, but you ignored it all. You deserve what you get you plantpot. Now eff off.

Reply to
Doctor Drivel

Of course you did - it's not one of your evil combis. Now tell your nurse to tuck you up again until the next election. If your liver hasn't given out by then.

Reply to
Dave Plowman (News)

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