Issues with thermostatic shower valve

[Elementour]

Hi Guy's,

Looking for some advice on an issue I have having with a recently installed thermostatic mixer shower in my ensuite. Everything was working fine for a coupe of months however now the valve has started misbehaving which is resulting in having to turn the temperature valve round further to get any heat but then once you get to the point that the water is warm turning even just a millimetre further means it can go from warm to almost scalding.

A couple of years ago we had a unvented cylinder installed and I have just checked it over and I dont think any of the cold outlets have been fed off the balanced supply as the valve that the cold mains comes into in the attached diagram does not have a balance supply coming from it and has just been capped off. I suspect that this may be the issue but im a bit confused as to how its not effected our other shower in our main bathroom or the old shower in my ensuite that i have recently replaced. Any advice welcome.

 

[Brambles]

Get the shower installer back. It is more likely to be a shower cartridge and / or inlet filter rather than the lack of a balanced cold supply.

If not balanced, the cold water flow rate will be equal or greater that the hot after a short period off running

 

[Elementour]

Get the shower installer back. It is more likely to be a shower cartridge and / or inlet filter rather than the lack of a balanced cold supply.

If not balanced, the cold water flow rate will be equal or greater that the hot after a short period off running

Unfortunately that would be me . My first thought was the shower cartridge but I read that they don't fail very often and its a brand new shower. I would swap it our to test but they cost almost as much as the whole shower did. I will take it out and give it a clean and see if that sorts it.