Solar panel, thermal store and electric showers...

[brackwell]

pt,
When the thermal is too hot how are you cooling this and is this satisfactory ?  I can see that a conventional shower mixer tap would significantly reduce pressure further.
Ken

[pt]

Ken, I do use a thermostatic mixer which was already in situ. The Zip literature says not to do this, but use a single supply and let the Zip itself take care of the temp regulation. Using a mixer unit does have the advantage of coping with the situation you envisage, ie water that is too hot coming from the solar store, so I haven't given any thought to how else to deal with that . However using a mixer valve has downsides such as restricting the flow, which to be honest I didn't realise, and the difference betwen the shower and the basin tap doesn't seem obvious. The other problem is that although I opened the mixer valve and moved the controller round as far as was physically possible, it still allows through a significant amount of cold water even when the temp  setting is on max. Presumably this is part of the anti-scald safety feature that the thermostatic control incorporates. What it does mean is that I have to run the ZIP unit at a higher temp to compensate for adding cold water at the mixer and this is obviously wasteful. On the other hand, cutting off the cold supply completely would isolate the sink as well, so at some point I have to go back in behind the wall and put an isolater valve in the shower cold supply. I've already turned the cold feed pressure to sink and shower down so you don't get luke-warm water when the Zip is having to cope with low temp input. The Zip does have an overheat temp cut-out but it is electronic, not mechanical, so only switches off the heater element not the water supply. Isn't your supply temp regulated at the tank end?  My mains pressure coil has a built in thermostic valve to prevent over-hot water being supplied.

[brackwell]

pt,
My DIY navitron system does not have a control on the hot water as my thermal tank is just a feeder for my real hot water tank which i was thinking of bypassing. There must be a easy solution to the mixing but i am not a plumber. In the old days there used to be seperate hot and cold taps which you mixed manually but not sure how they connected up.  I guess one way would be to feed the hot water to the shower head direct but T in a cold water supply controlled with a tap or perhaps the mixer
Ken

[KLD]

Ken,

A thermostatic mixing valve at the tank outlet is certainly a very good idea.  Your solar panels can then heat the tank during summer to higher temperatures, say 85°C, and that way you can store more heat for the subsequent two dull days. If you the were to feed 85°C hot water towards the taps  . On the downside, the TMV will always mix-in some cold water, even when the store supplies water below the set temperature. This is to allow for the safety shut-off in case of cold mains failure. Whether thermostatic shower mixer are the same in this respect, I dunno.

So, in short, if you install a TMV on the tank outlet and set that to, say, 45°C. then you could do away with the thermostatic shower mixer. The TMVs are available in larger DN, so you don't loose too much flow.

Klaus