Help with my Y plan heating system please

[Davelouaz]

hi everyone
I’ve noticed a small issue with my heating and it’s bugging me because I can’t put my finger on what’s causing the radiators to randomly come on when our Nest therm is off.
I don’t think the Nest is at fault because the heat link is not showing “Heat on” lights when the boiler randomly fires up.
I don’t think the valve is at fault either as it’s brand new, replaced last summer.
My only thought is it must be a frost protection setting as we are in winter and this mostly happens at night, although it’s happened today when it’s 6 degrees.
Is it normal though for the rads to heat up when this happens? Also the temperature on my thermostat shows high in the mornings, so there has definitely been a lot of heat throughout the cold nights, again when I don’t have any heat scheduled at all on my Nest.
I’m quite good with electrics and have done some process of elimination tasks, I’m convinced it is something to do with frost protection, but don’t know how to fix this, also my heating bills are rising, which is why I need to find this fault.
Any help would be greatly appreciated.

 

[heatservice]

Dont you just love these energy saving devices

 

[Murdoch]

If your heating bills are rising, turn the room stat down?

The only way to tell if your consumption is falling is recording the usage, every month, over a long period.

Also, remember this winter has been colder than the last couple!

 

[Harvest Fields]

Unfortunately last summer is not new. A valve is only as good as long as it has been sat on someone’s van. (Could of been on there 18 months before he fitted it). It is the first place to start. Put the hot water only on and see if the pipe to the rads gets hot.

 

[dan_the_plumber]

Your Nest should be wired, Live and Neutral. Then also ports 2 & 3.
A lot of stats are ports 1&3