Intermittent fault on central heating on baxi duotec

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Hi, wondering if anyone can give any thoughts as to what is going on here.

We have a Baxi Duotec boiler, with a wireless Siemens thermostat attached, from memory I think that's the RDJ10 RF. They worked fine together for a number of years.

In the past few months we have had a few occasions where the heating will not come on, although hot water is being supplied on demand as normal. What I see is that when we turn the thermostat to the daytime setting, and the temp is low enough that the thermostat calls for heat (we see a little triangle on the display to show that it is calling the boiler), the boiler does not respond.

There are no error codes on the boiler. It doesn't have a manual switch so unfortunately I can't press that to try to get the boiler to produce heat without the thermostat. The first time this happened, we waited several hours (we were out of the house so left the heating as it was), and then tried to put the thermostat on again, and the boiler fired up as normal.

The only way I seem to be able to get the heating to work again when it stops, is to turn the thermostat to the Off setting and wait 2-3 hours. It then usually comes back on.

What I've tried so far:
I've turned the boiler off and reset it completely, to no effect.
I've reset the thermostat to factory settings and re-paired it with the boiler, to no effect. When the boiler refuses to work, I've checked the cconnection to the wireless receiver from the thermostat and the little light shows that it is connected correctly. We get no errors on the thermostat, the display is working fine, so i don't think it's a battery issue on that either.

We have called an engineer out several times, but due to the waiting times, by the time they come out all they have to do is flick the thermostat and it comes on. They then announce that they can't do anything if it's working, and leave. It's getting quite annoying now as the problem is becoming more frequent, at it would seem that we aren't going to get any resolution at all with an engineer until whatever is at fault packs up completely.

I'm finding it hard to determine if it's the thermostat itself at fault, the connection from the receiver to the boiler, or the boiler itself. The only thing I can think to try is to get the thermostat replaced first as I guess that's the cheapest thing to try, but I would rather get to the bottom of the issue first if possible.

Any help would be greatly appreciated, cheers!
 
Why dent you link out the receiver that way you can prove if its the boiler or external controls
 
Hi Algas, thanks for your reply. I'm sorry I'm not quite sure what you mean, I haven't got a lot of experience in boilers. I've had a search of the site and couldn't find any instructions on what you're suggesting.

Is there any info you could point me to so I could follow your suggestion? Thanks again.
 
which company does the engineer work for? or is he an independant?

the guys who work for the big companies have schedules to stick to. if its an independant, ring someone who comes recommended.
 
Exactly call an independent!

I expect its a receiver fault.

But what make of batteries in the transmitter unit and how old are they?

Tony
 
Not sure of the company he worked for as my parents arranged it, but it was through our house insurance (the home emergency cover), so I assume he was working to a schedule and probably pretty tight guidelines on what they can do.

We had the boiler installed by an independent engineer a few years ago, he was reliable and good but not cheap. I think he might be our next port of call, but I'll have a look at the batteries when I get home incase that's a cheap fix. I was assuming the batteries couldn't be at fault as there's no warning on the thermostat and it seems to be working fine, but still worth a try.
 
Well, I have replaced the batteries on the thermostat because the battery sign flashed this morning, and re-paired the thermostat to the receiver again and no joy.

The heating refused to come on again this morning even though I've been turning it off overnight, and replacing the batteries hasn't fixed the issue. I'm thinking I'm going to have to call out the engineer who fitted the system in the first place.
 
What make/type of batteries did you fit?

The current demand is very high on transmit and only alkaline types usually work. That generally means Duracell.

It could well be a faulty power supply capacitor in the receiver. They lose capacitance and dont provide enough voltage to reliably operate the relay.

If thats the case the capacitor can be changed by a keen person with electronics skill. But most heating engineers would not be doing that and would need to replace the receiver.

Usually a wireless stat pair has to be bought which gives the opportunity to change to a more suitable type if further facilities are needed.

Tony
 
Thanks Tony, the new batteries are indeed Duracell.

I'll let my other half know your thoughts as he has done some electrical work before, failing that we will suggest it to the engineer and see if there's anything he can do.
 
I suggest putting linkwire back into chock block if other half up to it. This I think will prove its a faulty receiver. See manual for details. No gas work involved
 

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