Baxi Duo Tec

17 Aug 2015
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United Kingdom
Baxi Duo Tec Boiler with thermostat
Hot Water kicks in OK

Dont want the rads on at all - so have turned all the dials on all the radiators to "0"/off and set the boiler dial to the lowest temp.
at around 5am I can hear the pump and boiler kicking in, so i go downstairs to look at the boiler and yes it is on, the radiator light is green and the boiler is working, but the pilot light isnt on...
so i decided to twist the nearest radiator dial to 5 and it filled up really quickly and was hot.
I took a morning off work and the boiler continued to kick in all morning...I wonder if it has been doing this every morning?!!

How do I stop this boiler trying to heat up radiators that a thermostat has not told it to do..
Last edited:
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Have you actually turned the clock to boiler off or the room stat down ?
erm... the dial on the boiler for the CH (its a radiator sign) is turned down to minimum - the hot water dial is around 3/4 round think that's 50.
The thermostat has a sitting temperature at 20 degrees. The thermostat is not telling the CH to come on (as it doesn't have that fire sign on it) it just appears that the boiler is warming up the water to heat the radiators (although the pilot light isnt on) I can just hear it for hours in a morning.
I turned it off all day yesterday (at the switch on the wall - so no power) - got home, turned it on, ran some water to wash up - and it was doing it again, the radiator side was lit and the fan/pump whatever it is, was on - its like its ready to go all the time?!

What should the thermostat be set at? to come off and on anyway?
I dont think the duotec has preheat (could be wrong) so maybe faulty frost stat ( thermistor gone out of range ?)
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thermostat doesnt have an off. It has 5 interval timings - which i have set but obviously cos its summer I have put the temps right down.

1 05:00 14'C
2 10:00 5'C
3 12:00 5'C
4 14:00 5'C
5 17:00 14'C
6 23:00 5'C

Infact i've just had a thought - if it sits 20'C (thermostat reading) and i dont want it to come on at all - should i be setting every time interval to 5'C for the whole lot?

I wonder if the boiler is kicking in because its trying to warm it to the thermostat 14'c ??? (never even occurred to me this might happen)
but if the sitting temperature on the thermostat is 20'C would it not tell the boiler to kick in when it dropped to 14'C ? (or is that not the way they work?!)
That is how it should work (ie, if it reads 20 and is set to 14 it should remain off). Maybe it is duff, but it could be valve protection feature if the stat has one. What model of thermostat is it?
If you have the central heating temp dial turned right down on the front of the boiler I doubt its your stat bringing the boiler on.
Why ? right down isnt off it will still fire for short periods if there is a demand
Right down is 25c flow or thereabouts, the op said the rads get hot when she turned the valve on.
Is it a wireless stat/programmer ? Turn it on and off to make sure its still synced and the batteries are ok.
Yes it would feel hotter than it did without the valve being turned on how hot is another question .The fault if any is external to the boiler
yeah got a salus wireless (radio frequency one) This morning I resynced it and reset the thermostat - tested it by putting the temp up and yes the boiler kicked in as it should with the Radiator sign illuminated on the boiler - put the temp down and it turned off...So far so good.
Will check it again tomorrow at 5am when I can (normally) hear it starting up!

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