It occasionally just fired up and started heating the radiators ... then went off on its own. in fact it still does.
However, I now know what (apparently) is causing it.
The installer looked at it but didn't know what was causing it (and it wasn't doing it when he called so tricky to diagnose).
Ideal sent an engineer who immediately said the problem is caused by the wireless Halo head unit/thermostat not being able to send a strong enough signal to reach the boiler (sited in an attached garage). The boiler is on the wall between the house and the garage so not all that distant, but the head unit shows a red signal instead of a green one unless you put it within a few feet of the dividing wall. The Ideal engineer said either mount the unit wherever it is capable of sending a signal capable of reaching the boiler - or fit an Ideal Halo Zigbee Booster (Part no. 221132). He said the boiler fires up, for a short time, when the signal completely disappears .... it has happened four times to my knowledge with the rads getting warm then going cold again. I only know it has happened if I happen to hear the boiler fire for no apparent reason - or I happen to feel a rad and it's become warm to the touch.
No-one has them in stock, not even Ideal. They say it will be in stock in 10 days time. We've ordered one (£24 plus VAT)
If it works I'll be happy enough to cough up the extra for the booster. If it doesn't then a bit more investigation will be required. But I would imagine it will. The engineer seemed confident. He did say it's not a warranty issue and he doesn't keep them on his van.
I post this primarily as a matter of interest and, maybe, it might be of some help to anyone with the same sort of problem.
However, I now know what (apparently) is causing it.
The installer looked at it but didn't know what was causing it (and it wasn't doing it when he called so tricky to diagnose).
Ideal sent an engineer who immediately said the problem is caused by the wireless Halo head unit/thermostat not being able to send a strong enough signal to reach the boiler (sited in an attached garage). The boiler is on the wall between the house and the garage so not all that distant, but the head unit shows a red signal instead of a green one unless you put it within a few feet of the dividing wall. The Ideal engineer said either mount the unit wherever it is capable of sending a signal capable of reaching the boiler - or fit an Ideal Halo Zigbee Booster (Part no. 221132). He said the boiler fires up, for a short time, when the signal completely disappears .... it has happened four times to my knowledge with the rads getting warm then going cold again. I only know it has happened if I happen to hear the boiler fire for no apparent reason - or I happen to feel a rad and it's become warm to the touch.
No-one has them in stock, not even Ideal. They say it will be in stock in 10 days time. We've ordered one (£24 plus VAT)
If it works I'll be happy enough to cough up the extra for the booster. If it doesn't then a bit more investigation will be required. But I would imagine it will. The engineer seemed confident. He did say it's not a warranty issue and he doesn't keep them on his van.
I post this primarily as a matter of interest and, maybe, it might be of some help to anyone with the same sort of problem.