A week or two ago my daughter asked me to have a look at her CH.
The heating was very intermittent. She had a Siemens thermostat in the sitting room with a wireless receiver in the airing cupboard upstairs alongside the combi. No heating.

On checking on the web I found that it was suggested that the the Siemens receiver might have a known problem with a "sticky - relay" that could be corrected with a rap of a knuckle.

This simple & temporary fix worked & I suggested that she had a word with the Co. that did her CH about 2-3 years ago to see if this is a known problem & could be subject to a warranty fix.

The fitter called & confirmed that it was probably a "sticky relay" & said that since Siemens don't sell the receiver unit alone he would have to replace to thermostat & receiver. He charged over £100 for this wisdom.

He went on to say that it could be possible to "clean the relay" (see below *) but it would be better if she re-installed with Honeywell kit, which is better!

Two days ago my son called me to say that his partner's property had problems with its CH. Yes, another Siemens system installed at a similar time. Similar symptoms. Same installer/fitters.

So I replaced my daughter's kit with a Honeywell ChronoTherm system. It is now totally OK as the fitter had suggested.

Amused by the fitter's observation that the relay is the failing unit & could have some dust in it, I took the failing Siemens receiver apart. The relay is a sealed component and I suppose I could unsolder it & replace, fixing it seems a bit extreme. He was talking ********, unless, of course he knew that Siemens were buying sealed relays from dusty Chinese Cos.

BTW: A neighbour had two Siemens receivers fail - allegedly due to a power outage - he has a big house with an upstairs/d9ownstairs system.

Coincidence: Possibly but it may be that Siemens is selling something that ain't fit for purpose.

Thoughts ????