Baxi HE 80 plus intermittent CH timing problem

[Chris]

Hi,

I have a Baxi 80 HE plus which firstly works fine for the hot water system.

However for the central heating several times a week, the Central heating does not come on as per timer controls. Although the lights on the timer control light up as expected when the timer is set to swich the heating on, the boiler does not fire.

However with several goes at switching the timer control on and off e.g. clicking advance or boost and pressing the reset button on the boiler , the Central heating will eventually fire up ( 2 green lights) and stay on until the timer control switches it off later in the evening.

There are no red fault lights showing on the boiler when it doesn't fire- in fact when it doesn't fire up there are no green lights either showing on the boiler.

The pressurised system is just over 1 bar.

Any ideas if this is more likely to be a timing control (Drayton Tempus

7) which I could easily get replaced or a boiler problem ( lots of money)!

Thanks for any help

Chris

[Mr Pounder]

My pressure is 1.5 bar. Worth a go?

[Rick Hughes]

You can download a Baxi HE diagnostic chart, it will tell you if red, green. flashing or no lights has a reason. I used it to find out one of temp sensor faulty ...

If you can't find it on Baxi ... ping me a PM and I'll email you a copy ... at least it may tell what is at fault Boiler or timer.

If it were me and it was due to com on and hadn't I check across timer contacts ... but that depends how you feel about testing such things.

[Andrew May]

Are you sure that the boiler doesn't fire or does it fire but then go out. The later might indicate that the flame sensor is not working as it should.

[Chris]

Thanks for the replies it's given me somehwere to start

Cheers

[ss]

Not that I understand these things but my previous boiler (not sure which name) had a problem of not coming on and I traced it to a kink in the condensate tube, I believe there is a pressure switch on some models and this kept the boiler from firing intermittently when it had water in it.

[Brian Gaff]

If you are saying that even a manual start will not start it and there are no errors, then assuming you are attempting to start it from the control, surely this means the control is not telling the boiler to start hence no errors, or did I miss something, its been a funny weekend.

Brian

[Roger Mills]

Are there any motorised valves in the system? If so, you could have a problem with one of those. Assuming that your boiler isn't a combi (I'm not familiar with the model, so I don't know) you may have a motorised valve for each heating and hot water zone. If it's an S-Plan system, the timer/room stat will control the valve and the valve will switch the boiler on when it's open. So if the valve doesn't open, or if it does open but its auxiliary switches don't work, you'll get no heating.

Could this be your problem?

[ARW]

I'll raise your 2 port valve with a faulty mid position valve:-)

[Roger Mills]

Yes, indeed. If it's a Y-Plan system, an intermittent problem with the

3-port mid-position valve could well cause the OP's symptoms.

[Big Les Wade]

I'm having exactly the same problem and I have come to the exact same conclusion. It seems the valve itself has become sticky, and the actuator motor cannot manage to shift it to the fully open position after a whole night switched off. (It opens and shuts it OK during the day, just as the OP's does.)

I haven't yet replaced it because it'll mean draining down the system etc, and then there's the worry that the valve has been on 20 years and may not come off very easily :(

But soon ...