Baxi thermostat...driving me crackers

johannis

Either I have lost the plot or our thermostat is knackered.
We can't seem to stop the boiler coming on, even though it was turned to a setting where it should only come on if the temp dropped below 10dgrees it was happily pumping out heat...26!
I can find no sensible guide to working modern thermostats online and while I thought I understood the principle I'm obviously wrong.
Can someone give me basic advice on setting a thermostat for summer so I can ensure Ive not done something stupid before assuming something is broke?

StopIt

Which thermostat have you got?


I have a Baxi Wireless thermostat and while it took some getting used to, it works very well, with night and day temperature targets, holiday mode, the mode you're seeking works too as we tested it. It's now firmly set to off.


Take a picture if you can and I'm sure someone here can help figure it out.

molerat

May not be the thermostat at all. Stuck valves can call for heat irrespective of what the controls ask.

matelodave

Do you get hot radiators when the you should only be getting hot water, if so then it could be a stuck diverter valve.

You need to be a bit methodical with trying to diagnose a fault. Find the pipes that feed the heating and hot water tank and check that the correct ones get hot when the appropriate thermostat calls for heat (tank or room).

You need to understand how the system is wired and configured to check what should be happening before you can decide what's gone wrong.

Cardew

molerat wrote: »

May not be the thermostat at all. Stuck valves can call for heat irrespective of what the controls ask.

I don't think a stuck valve will call for heat. As matelodave states above if hot water for tank is switched on, a stuck diverter valve could incorrectly divert that hot water to radiators. Switching off Hot water should eliminate that issue.

However my understanding of the OP's post is that Central Heating is being demanded even though the thermostat is turned down to 10C.

If it is not 'finger trouble' it seems more likely to be an electrical problem.

Are there reset buttons on the boiler/remote thermostat? You can also try switching off power to boiler and remove batteries from thermostat, then install batteries and try again.

StopIt

If the OP has the thermostat I have it's easy to eliminate it from the consideration.


It has a nice indicator to tell you if it is actively telling the boiler to turn on. if that's not coming on and the boiler is still firing, it's something else.


It may still be operator error at this point, depending on the thermostat! I think I know what MAY be the issue, but will hold fire until we get the OP back.

EachPenny

Cardew wrote: »

I don't think a stuck valve will call for heat.

I think what molerat was saying is if the diverter valve has auxiliary contacts used to call for heat then if the valve is stuck the call will be made regardless of what the thermostat(s) are doing. My system is set up that way, the thermostats control the valve, the valve controls the boiler.

Although obviously only applicable if this is what the OP has too.

StopIt

EachPenny wrote: »

I think what molerat was saying is if the diverter valve has auxiliary contacts used to call for heat then if the valve is stuck the call will be made regardless of what the thermostat(s) are doing. My system is set up that way, the thermostats control the valve, the valve controls the boiler.

Although obviously only applicable if this is what the OP has too.

Yep, because my Baxi may not be controlled that way.


My Thermostat talks to a radio receiver connected to the boiler. When it calls for the heating to be turned on, it turns on the boiler electronically, and tells it to turn the central heating on.


It even has a time lag which at first confused us! It tells the boiler to turn on, but the boiler wakes up, waits for the thermostat to stay on for long enough, then fires up the gas.


Where-as if I turn the hot water on, the boiler detects this differently and switches the gas on instantly.