Boiler trouble. What should I do to fix it before calling an engineer?

[ihatethecold]

I have a combi boiler that had a new timer fitted in summer.
Last night the hot water was only lukewarm and the heating wouldn't go off.

The house was really warm at 10pm.
The heating is set to go off at 8.30.
My DH manually switched the timer to off so in theory no heating should be on.
This morning the house is like a sauna.
It's saying it's 23deg.
I don't even set the temp that high ever.
How is the heating on when I switched the timer off?

Plus the hot water is still lukewarm.
On the boiler the dials haven't moved for the water/boiler temperature.

What can I do?

Find the manual or Google the model for online user guide. There's usually a trouble shooting guide...

You could try the reset button?

I think I would get plumber in though really.

Depending on type of boiler, it could be the valve in the airing cupboard, if you have one.

Valve is a solenoid and might be stuck, just need to manually switch it over.

It has a small lever on top of it, next to hot water tank

If that has gone, needs replacing and a plumber job I.e. Drain system to below level of valve etc

What Hoof said above

We don't have an airing cupboard. The boiler is a combi one so there is no tank.

EngTech is probably right. I've just had the same but with my hot water.
Everything shut down but the boiler kept kicking in and hot water was ridiculously hot. The valve had got stuck, had to be replaced in the end.

I've cut the power to the boiler and timer for a few mins then started it up again.
Water is still lukewarm.
I'm taking my dogs out now. Hopefully the radiators will have cooled a bit so I know they are not constantly heating when the timer is off.

You mention a timer.

Is there a wall thermostat?

Do any of the radiators have thermostatic valves?

In the middle of the night, when you have not run a tap for a couple of hours, are the radiators still hot?

Do the radiators get particularly hot when you run a bath or shower?

Yes there is a wall thermostat on the timer. Ive had to switch the boiler off at the mains to cool the rads down

The rads all have valves on them. they are not fully open so the heat distributes evenly though the house.

Ive just switched the boiler back on and the timer is off. my rads have got very hot again.

is it a wireless thermostat?

if you can post a photo of the timer, and any control on and around your boiler, that may help.

no its not wireless, Ive called the heating engineers to come and take a look sometime, hopefully today.
They fitted the timer about 6 months ago

Photos

Honeywell CM907 programmable thermostat, very good device.

You mention the hot water being lukewarm, so I suspect the diverter valve, but behaviour is odd. If yours is an oil boiler they are not so common and I don't know what it might be.

ok thanks, yes its oil, the engineer will come tomorrow morning and take a look.