Can you use a mixer sideways?

[PCPaul]

Daft question, probably..

I've been tracing the pipework on our cowboy-installed 'solar preheat' system.

It would appear that they fed the cold inlet pipe to the solar panel, then took the warmed output into the 'mix' *output* of a thermostatic mixer valve. The 'cold' and 'hot' inlets to the mixer are, naturally enough, connected to the cold inlet to the boiler and the hot *outlet* from the boiler.

So, a couple of Qs...

- can a mixer be used sideways/backwards like this? (I suspect no)

- How come it seems to work anyway, although without any noticeable solar benefit?

For extra credit: why is there an expansion tank tee'd onto the pipe from the hot side of the panel to the 'mix' side of the mixer?

hmm.

[dennis]

No idea but it can't work properly unless there are sensors on the panel and where the preheated water is stored. What do these connect to?

[PCPaul]

Ha. You're so far ahead of this system it's unreal.

This is the one I mentioned a week or so back - appears to have been installed by numpties who had heard of solar but never seen it.

There's a decent evacuated tube panel. A thermostatic mixer (not externally controlled, just a plain thermostatic mixer like you'd use to limit tap temperature in an old folks home). A modulating combi boiler. And that's it.

No sensors, no preheat tank, no controls.

AFAICS the plan was to instantaneously preheat cold mains water before it went into the combi, using the thermostatic mixer to limit the temperature (It's a Vokera - they say it can't take more than 20C on the input...). But even that hasn't been done right.

I'll draw a diagram and post it somewhere for you all to marvel at...

[meow2222]

I reckon thats needed - and suspect the system may need a replumb to work.

Consider how a mixer valve works: it adjusts the relative resistance of hot in to output and cold in to output, according to the temp on the output terminal. So it should be poss to figure out what its doing in your setup, and thus whether what its doing is functional in any useful sense. Will wait and see what you've got, no storage sounds pretty useless though.

NT