Can anyone diagnose what is wrong with my boiler before I have to call out the plumber who charges £60 just to come out on a weekend.

[WeAreEternal]

My boiler have been 'on' all day, as in firing, burning, making the noise that it makes when you run the hot water or have the heating on.
Except that no water is running and the heating is off.

occasionally when it is cold (so most nights) the boiler fires up for short periods, I assume this is to stop the pipes or whatever getting too cold and/or freezing.

However, today it has just been going none stop for no apparent reason. It isn't that cold here today, 3 degrees, so I don't see any reason for it to be on.

I have checked the heating, and all of the taps, all definitely off.

The display on the boiler says 'Pump Overrun', Although I'm not sure what it usually says when nothing (hot water/CH) is running.
I have checked the manuel and 'pump overrun' is listed in the display functions section under 'normal operation modes'
So it doesn't appear to be an error message, but it doesn't exactly sound right either.

The hot water and CH are both working fine but since I cant figure out why the boiler is running continuously I have switched it off.

Does anyone have any idea?

What make is it?
If its a worcester they have an excellent technilal help line, it could be any number of things, but to be honest they are best left to professionals remember Fizz in Corry?
Can you hang on till Monday and is call out cheaper then?
One simple thing you can do your self is to turn the electricity off to it, wait a few mins then turn it back on, it should then do a start up type self test thingy, it may reset its self

Is it a combination boiler, rather than a tank?
If it is a combination boiler when all taps are off and the thermostat is turned right down then the boiler should not fire up even if switched on.
Check the thermostat is working, it should click when you turn it up or down to switch off or on. The thermostat could be broken.
Is there a pressure gauge on the boiler? If that is at zero then you may need to charge up the system .
To charge it there should be some sort of valve below the boiler that you turn which allows mains water into the system to charge it up. Shut it back off when the pressure reaches 1.5 bar.

Personally, I don't think it's your actual boiler but something within your central heating system making your boiler think that hot water is being called for. My guess is a stuck/sticking motorised valve. Basically, they look like little metal/plastic boxes (mine is located in my airing cupboard). Google for typical pictures. Turn off your heating & hot water & if the metal box is vibrating, then it probably is that. There is a little lever on the box that you can manually move to open/close the valve - chances are, some water has leaked in the past or limescale has built up & made it stick.

Your hot water may feel hotter than usual if it is the valve.

When our boiler did this is was a problem with the diverter valve (ours was in the airing cupboard alongside the hot water tank). We put it on override until we could get it fixed/replaced during the week.

well?

is it a combi or have you got a hot water cylinder?

It sounds like a faulty/incorrectly located frost thermostat to me.. It is there to protect the boiler during very cold conditions.

With more information we could probably give you a better answer though! Along with the above questions, could you also let us know where the boiler is located? i.e garage, kitchen etc. And how long the boiler has been installed?

I think £60 is a reasonable amount to charge for a weekend and wouldn't hesitate to get a GasSafe registered engineer to ensure that everything is operating safely and correctly.

Hope that helps! Dennis

I'm assuming your thermostat/boiler has a standard frost setting of 5degrees C. So if it's 3deg then your boiler will automatically kick in and run until the temperatures rise above 5degrees.unless you lower the temp of the frost setting, if this temp adjustment is available. Otherwise you'd need to disable this. I wouldnt advise this though. When a boiler is running on frost settings it is quite economical and so it wouldn't be costly.
Pump overrun is a standard feature on most boilers. It's a safety measur and a normal operation. The pump runs for a short period after the heating is turned off, to take away any hot water from boiling and damaging your heat exchange. A normal operation. ??

I think, since January 2013, it has probably been mended by now
.

I have a keston Celsius 25 boiler the hot water thermostat is stuck between on and off so is on permanently even though I have turned boiler off cen. Heating is ok.how do I just turn hot water off.can anyone help.

I guess if the switch is broken physically, you need either a heating engineer or an electrician depending whether it's in the boiler itself or not.
Unless you feel competent to replace it yourself, which I'm guessing not.