Strange Radiator/Boiler problem


Hi all
We have a glow-worm space saver Mk11 Balanced Flue Boiler in the kitchen, which is used to heat the water and supply the radiators when heating is required. Upstairs in the 2nd bedroom there is a cold water tank and hot water tank with an electric emersion heater.(never used).Also a motorised Mid Position valve (V4073a). Today on returning home from work, the hot water has come on via the combi boiler(no heating on) but the radiators downstairs were all red hot, even though the timer was set to hot water only and the thermostat in the hallway was on minimum.
The Boiler setup is a Y PLAN according to this site, if this helps..
http://content.honeywell.com/uk/homes/systems.htm
Any ideas???
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In an earlier contribution to this discussion,

I don't understand the reference to a 'combi' boiler. Surely, it's a conventional boiler providing CH and stored HW rather than 'instant' HW, isn't it?
When did you last consciously use the heating?
The most likely cause of your problem is that the mid-position valve has stuck, and isn't returning to the HW-only position - but that begs the question as to why it ever moved away from this position in mid-summer. In addition, I would have expected the upstairs radiators to be hot at the same time - unless they're all turned off, or are all fitted with TRVs which have been turned down.
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Cheers,
Roger
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Not too sure of how your system is set up. Is the combi connected as part of the heating circuit with the glow worm or are the two separate? Sounds like could be a problem with the cross connection bettween the two.
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wrote:

Hi sorry No combi just the standard Glowworm boiler.. HTH
Tony
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Tony & Debs wrote:

One possibility that fits the symptoms is the mid position valve is stuck, and you have thermostatic rad valves upstairs but not down.
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Cheers,

John.

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