Boiler Cutting Out After Short Period

[LynMc]

We have a Stelrad Elan Ideal Boiler (sorry don't know the model number) which is around 15 years old. Had a new Grundfos pump in the airing cupboard a year ago and all has worked well until recently.

Boiler comes on and heats the water all the time no problem. However, when you also want the CH on, the rads get warm but after around 30mins the boiler cuts out and will not come on again. Then when everything gets really cold we can get it to start it up again and if we then keep the heating on 30 deg it will stay on but if you put the thermostat down just a wee bit, it cuts off and does not work again until everything is cold.

We had a Landis & Gyr timer/programme switch which we thought was causing the problem as when we tried to switch off the CH to cool everything down the orange light for the CH only dimmed, we could not get the light to go firmly out. Once the light went out, this usually meant it had cooled down enough and we could usually get the boiler to work.

We changed the timer/programmer for the new Landis equivalent and this seemed to do the trick and for 2 weeks everything has been great. Now however the same thing is happening. The hot water works no problem but the heating only comes on for a short time and then nothing.

Hope someone can help

Thanks,
Lyn

 

[hi-spec plumbing heating]

sounds more like your wall stat if you have no control with it.

 

[bengasman]

Sounds like overheating. Does it happen when the radiators AND cylinder are on or with radiators only and cylinder off? As it sounds like an open vent system, my first guess would be corrosion or limescale. I doubt if more than 20 percent of open vent systems are clean, at least in my area.

 

[pannierstan]

Try checking the syncron motor in the mid position or zone valve depending on which you have.

Stan

 

[LynMc]

Thanks for the replies.

We can only have the CH with the Hot water - we cannot have CH only. But the boiler is OK when just the hot water switch is on the problem is only when we want the CH on as well.

If we knew what a syncron motor or zone valve was I suppose we could try !!!!!!

The boiler has two settings High and Low, for the moment we are trying it on the low setting and for now the CH is working but obviously not with a great deal of heat.

Lyn