Having previosly upset the better half by using all the hot water from the tank (heated by solar with the boiler switched off in the summer) is it possible to plumb an electric shower to the hot water feed from the tank so that it heats up the preheated water on demand. obviously, somewere in the system there needs to be a way to cool the water down when the solar is working properly.
Can you have a thermastic valve feeding the electric shower unit. do all electric showers work by just heating the water up and the temperature is controlled by flow, or is there a way of controlling the power into the shower? Thanks Glyn
Tony
posted on 12-04-06
You would need mains pressure hot water cylinder and an expansion vessel and blow outs. or a heat exchange unit to flow mains cold through getting its heat from the existing hot cylinder. Then before this water goes into the electric shower it would need to go through a thermal mixing valve. Even then the electric shower would need to be a thermostatic one and not a cheapo one.
That would work
fostertom
posted on 12-04-06
I'm told the fastest payback for any kind of eco-equipment is the heat-exchange waste pipe for use with electric showers. American, not sure if available here. 1m length of Cu waste pipe falling vertically from the shower waste, mcw pipe soldered spirally around it. A gd %age of the shower's waste-water heat is transfered into preheating the incoming mcw, effective because the incoming is so cold - gives big temp differential.
If incoming temp is 5o, showerhead temp is 40o, leaving the waste at say 30o and transfer rate is say 75% (don't know) then by my calcs 53.5% of the heat is recycled and you only use 46.5% as much electricity.
It works well for a single shower (or group of showers if you can bring all their wastes together) because the waste water goes out simultaneous with the hot water demand and incoming cold flow - for any other hot water use the waste goes out later.
It doesn't have to be an electric shower - it can preheat the mcw feed to a hw cyl feeding a shower or group of showers - the mcw flows whenever the shower(s) run(s), as well as at other, non-preheated times. Then your pv panel can take over, further preheating the tank - great way of storing irregular daytime solar energy for the evening or next morning.
Geoff
posted on 13-04-06
example of the heat recovery device that "fostertom" referred to.
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