Boiler & heating coming on at night

[FlySwimmer]

Our heating has 4 settings: On, Off, Auto & All Day. At night we set it to Off, and then turn it on manually in the morning. I’ve just woken up to notice that the radiators are warm & the boiler has kicked in! Why?! We have Frost Guard on the boiler, but I didn’t think this was meant to circulate in the central heating? Just a bit worried about the bill if it’s been regularly coming on at night. How do I stop it, aside from just switching off the power to the boiler, which I’m reluctant to do because of the Frost Guard. Is the Frost Guard a bit faulty? Something to do with the thermostat?

What number is the thermostat on? Probably it’s dipped below that in the house. Just put your thermostat on a very low number at night

Just put the timer on! Nobody wants to get up to a freezing cold house if it can be avoided.

This.

All boilers have a thermostat and it’s been really cold so it’s probably hit the anti frost setting. You might be able to turn the thermostat down. We have ours set to 10 degrees. (And then turn the heating on / up as we need to).

If it is a frost guard probably better that it goes on rather than water pipes bursting and needing a plumber. Even if you are renting it is probably your responsibility to keep it at a certain temperature.

Our thermostat is set to 19, but even when it’s been really cold during the day, but the heating has been set to Off, the boiler hasn’t kicked in iyswim? Frost Guard is set to 5 degrees, but I thought Frost Guard wasn’t meant to heat the entire system, just the boiler itself?

Frostguard is for the whole system. How would it stop pipes bursting if it didn’t send the hot water through them?

I suspect it’s the frost guard. That’s how it protects the system by circulating hot water to the rads.
The frost guard shouldn’t be set lower than 5 degrees C.
Burst pipes etc will be more expensive than the heating to prevent it.

It might be that your pump is stuck, if you have a less modern boiler/system. We had this a few times where the heating was stuck on.

@Thelondonone @Orangesare Maybe you’re right. The couple of articles I looked up on it though suggested it shouldn’t heat the whole system - the rads shouldn’t come on, etc. But while not absolutely ancient, our boiler is on the older side so it could be a different system to newer ones.

My boiler kept doing this, I suspected our control panel as boiler serviced. I’ve just had Hive installed and not happened since.

Do you have a hot water cylinder? Does your control panel have a timer for hot water as well?

@Droven Yes, the hot water has the same settings as the heat. It’s set to Auto, and usually kicks in around 8am for morning showers. So it can’t have been that as it was too early (plus the red light indicating it’s on on the control panel wasn’t lit - but neither was the heating one).

I don’t know if it varies between boilers, but when our frost stat setting comes on, the boiler kicks in and starts the central heating going to get the temperature above the set point.
I’d presumed that the intention with that was to protect the piping outside the boiler too.

The temperature sensor for our frost stat also used to be in the loft, which is the coldest part of our house.

Have a look near the hot water cylinder. Doe you have a brass valve with a plastic or metal box attached to it? Google three port valve to get an idea of what I’m talking about. What boiler do you have?

The anti frost settings definitely do circulate water around the system. In fact, on our boiler, the first thing the antifrost feature does is to start the pump to circulate water round the radiators.

If the boiler is in a cold area like a loft or garage then just pumping to bring in water from the radiators in a warmer area could well raise the temperature of the boiler. Only if this doesn't raise the temperature does the boiler actually fire up.