Boiler question

[Sabatinitennis]

I happened to be up at 4am today.
The thermostats in my six year old house are set at 21° and they showed a temperature of 17° in the house. Not a problem as the central heating system is set to come on only between 6am-8an, noon-1pm and 6pm-11pm.
But my new Worcester boiler started purring as was the water tank upstairs and on checking the green "on" light was illuminated on the boiler.
Any ideas why?? Because as a far as I know the thermostat next to the water tank upstairs is also set to the same times.

 

[Mottie]

Frost protection kicking in?

 

[dilalio]

Did the rads warm up or just the cylinder?
Could be weather comp or smart stat ensuring the room temp "IS" 21 @ 6am and not "starts" warming to 21 @ 6am.

If cylinder only, could be anti legionella program running.

What controls do you have?

 

[Sabatinitennis]

The rads stayed cold.
As I understand the system was pre-set when installed to come on between the hours shown. If I knew how to load up a photo on this website I could load one up of the thermostat next to the water tank and the boiler.

 

[ianmcd]

Bottom right hand corner, select "upload a file" then select your pic then "post reply"

 

[durhamplumber]

I happened to be up at 4am today.
The thermostats in my six year old house are set at 21° and they showed a temperature of 17° in the house. Not a problem as the central heating system is set to come on only between 6am-8an, noon-1pm and 6pm-11pm.
But my new Worcester boiler started purring as was the water tank upstairs and on checking the green "on" light was illuminated on the boiler.
Any ideas why?? Because as a far as I know the thermostat next to the water tank upstairs is also set to the same times.

Some boilers start up regularly to prevent pump seizing up.

 

[Sabatinitennis]

Thanks. I'm told too that when the setting reads 6am-8am, the 6am is not the time the boiler starts heating the radiators, but that the boiler comes on earlier to ensure that between 6am-8am the radiators are at the requested temperature. Quite amazing.

 

[dilalio]

Thanks. I'm told too that when the setting reads 6am-8am, the 6am is not the time the boiler starts heating the radiators, but that the boiler comes on earlier to ensure that between 6am-8am the radiators are at the requested temperature. Quite amazing.

That's what I was referring to in my post above about smart stats.

 

[Madrab]

You have a CM907, which has an 'optimum start' feature.

As @dilalio suggests it's has smart tech, it monitors the temperature and will start the central heating early to ensure the space is up to the required temp by the required time.