Moira Niedzwiecka Posted October 13, 2017 Share Posted October 13, 2017 Please help. We are building a 2 bed chalet style house with a bathroom and a shower room. There are only two of us and we rarely have anyone stay as all friends & family are local. The house is built to passive standard but not going for certificate. We have 3.9kw of PV going on the roof. We are not having a boiler or heat pump. In our present house we just use an immersion to heat the water & we are all electric. We pay £41pcm for all our electricity at the moment. I do not really understand the difference between a thermal store & a UVC & what would work best for our new build for the DHW. Any suggestions? Link to comment Share on other sites More sharing options...
ProDave Posted October 13, 2017 Share Posted October 13, 2017 The key difference is how they store the heat. With a UVC the water stored in the tank is the water that comes out of the tap. Of you heat it to say 55 degrees, then when you turn on a tap, water comes out at 55 degrees and continues to do so almost until all the hot water is used up then goes cold very quickly A thermal store stores it's heat in a static volume of water that never changes. You draw water via a heat exchange coil. So as soon a you start removing heat it starts to cool down. So if that wa heated to 55 degrees, the hot water would start at that, then start reducing in temperature. So you will in practice have to heat a thermal store hotter to get the same amount of usable hot water from it. The advantage of a thermal store over an UVC is the lack of requirement for over pressure valves etc and need for discharge pipework, and in theory at least you need a qualified plumber to install a UVC. Link to comment Share on other sites More sharing options...
PeterW Posted October 13, 2017 Share Posted October 13, 2017 The issue you will have is size - a small UVC will be 180 litres and the equivalent TS you would want 250 litres to get anything like reasonable storage in it. TS is useful to run UFH too as a buffer - if you’re not having any wet heating then I can’t see any benefit to a TS other than you tend to heat them hotter which means more PV capacity. In in your instance I would very seriously consider the SunAmp - check out @JSHarris and @TerryE blogs as that will give you everything you need in something the size of an undercounted fridge with low losses. Link to comment Share on other sites More sharing options...
Moira Niedzwiecka Posted October 14, 2017 Author Share Posted October 14, 2017 Thank you for the info chaps. What is proposed at the moment is a UVC with a back up immersion & an 'I Boost' to send any excess PV to the UVC. I have looked at the Sunamp as suggested & basically do not know what it all means. Sorry to be so dim. Does the sunamp replace the UVC? Would I still need some sort of a cylinder & the PV 'I boost'? Link to comment Share on other sites More sharing options...
PeterW Posted October 14, 2017 Share Posted October 14, 2017 The SunAmp replaces the UVC and the PV diverter. It basically uses the PV or E7 electricity to heat a phase change salt - bit like a heat pad with the clicker in that you normally redo in hot water ..? very efficient, and very low losses to the building. Link to comment Share on other sites More sharing options...
Moira Niedzwiecka Posted October 14, 2017 Author Share Posted October 14, 2017 Peter, Thank you for explaining that. One of the reasons we were considering a UVC was because of mains pressure hot water to the showers. How does it work with a sunamp? Sorry to keep bothering you but you explain it in terms I can understand. Moira Link to comment Share on other sites More sharing options...
Barney12 Posted October 14, 2017 Share Posted October 14, 2017 Have a watch of this. Provides a good basic intro: Link to comment Share on other sites More sharing options...
Moira Niedzwiecka Posted October 16, 2017 Author Share Posted October 16, 2017 Hi guys I have just spoken to Sunamp. Interesting stuff. They are sending me further info. Thanks again. Moira Link to comment Share on other sites More sharing options...
SteamyTea Posted October 16, 2017 Share Posted October 16, 2017 On 10/13/2017 at 17:41, PeterW said: a small UVC will be 180 litres and the equivalent TS you would want 250 litres I beg to differ. My Economy 7 vented cylinder is 200 lt, I only heat it to 50°C and did two of us no problems. If I had heated it higher, it could have coped with more. Did I not hear (on here) that an unvented store also needs an annual check from a qualified person as well as being installed and certified by a proper plumber. An ordinary vented cylinder does not need that, though it does need a feed and expansion tank above it (a UVC needs a pressure vessel to do the same I think). You can easily get a decent shower by fitting a small, twin impeller pump. Mine delivers 10 lt a min to the shower and double that to the bath. Been in over 10 years now and has not given problems. My vented E7 cylinder is 30 years old and the bottom element has finally given up the ghost, so just using the top element (so built in redundancy as standard). All in all, I think the easy and simplicity of a vented system and the fact you can DIY it is a big advantage. Link to comment Share on other sites More sharing options...
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