Cosy wireless star new boiler issue

[singled5678]

I had a new Worcester boiler fitted and ever since had an issue with my Cosy wireless stat, that's always worked fine.

It fires up the heating and water, but when the temperature drops below what is set on the stat it doesn't fire the boiler/heating back up.

Does anybody have any ideas?

The person who fitted the boiler has been a couple of times and I've had no luck as yet. He's changed the 3 port valve as at first I couldn't get hot water, without the heating on. Now I can just this issue with temperature drop.

Thanks for your help.

 

[stem]

When the problem occurs, i.e. the temperature falls and the heating doesn't come on, what colour light is showing on the Cosy display? It should be magenta. [A green light = up to temperature, a magenta light = heating 'on' and a blue light = 'off'.] If it isn't showing magenta, then there is a problem with the Cosy not switching.

I assume the installer has checked the various Cosy components are all communicating with each other.

From your original post my understanding is that only the boiler is new, and that the rest of the system including the Cosy was already there and working OK. But there is something a little bit odd about this though because you say that...

He's changed the 3 port valve as at first I couldn't get hot water, without the heating on.

The 3 port valves default setting is 'hot water only' which it is pulled to by a strong spring (the motor winds it to the other positions) and for hot water, the boiler is controlled by the thermostat on the hot water cylinder, so if the valve failed you would still be able to get hot water. In fact that is all that you would get.

OK you say this is resolved now, but I suspect that there may be something wrong with the wiring / installation, but without being able to physically able to check it's difficult to say what.

The 'Cosy Switch' has a control button that allows you to revert to the original controls, can yours do this? and if so, what happens when you override the existing controls, does the heating come on now?