electic shower + preheated water

[sm_jamieson]

Yes, before we start, I know electic showers are not designed to take a "hot" input. I would like to pre-heat the input water to an electric shower, such that it's performance is a little better than in the summer. Input temp of, say 18 C ? It should not nick too much capacity from the combi, as this is designed to get 2 shower working at once to reasonable performance. Anyone know about DIY heat exchangers, water blending etc ? The system should be fail-safe, i.e. so the input water temp cannot exceed a level and damage the electric shower. I think this could be a very useful solution. TIA, Simon.

[PeTe33]

Surely you would want to improve performace in the winter i.e. when cold water is at it's coldest?

In which case, some form of heat exchanger from the C/H return pipe may prove beneficial to take the "chill" off the water whilst cooling the return water to the combi. assuming it is a condening bolier.

then again, I may be talking crap!

:¬)

See my home made heat exchanger on the "pipes under floor question" thread. I chanelled and boxed the final item in a cellotex surround, but for a hower I guess you would need a much more efficient heat exchanger.

[Alex]

If your shower doesn't heat the water to a "hot" state, them maybe it needs fixing?

alex

[Dave Plowman (News)]

If you've already got a (presumably) gas combi why do you want to pre-heat water with gas then spend much more money heating it the rest of the way with electricity?

[sm_jamieson]

What ? What is "hot" ? Elect shower performance depends on input water temp. It is well known that they are pathetic in the winter. Simon.

[sm_jamieson]

Yep. The thing is, if someone uses the other shower (combi), the central heating switches off. But I suppose there is still a bit of heat in the system to be used. I suppose a thermostatic mixer set to a very low temp, that takes a very low flow from the combi would work. I think it would be hard to regulate. I know. A small multipoint. But then - why not get 2 combis ? Simon.

[isthatthetime]

You can get thermostatic mixing valves that I think are used for the hot taps in childrens nursery basins and care homes etc to stop the hot water being too hot...

[isthatthetime]

That link to scewfix shows one with a preset temperature - don't know if you can get a variable one?

[sm_jamieson]

Oh, I didn't explain v. well. Average combi is not good at suppying 2 mixer showers together (e.g. bathroom + en-suite). A common solution to tthis is to have thermostatic mixer in bathroom, electric shower in en-suite. Now, combi for bathroom, a little of combi power + electric shower for en-suite. Seemed like at good idea to me ...(!) Simon.

[Alex]

My electric shower takes in cold water, and at the highest setting the water would give you nasty burns!

alex

[sm_jamieson]

Does it do that even in winter ? If so, what make and power is it ? Also, why have I read loads of posts about how feeble electric showers are compared to combi boiler / mixers ? If your shower can give you good pressure at a very hot temperature even in winter, what are the previous posters going on about ? If such a shower as you describe can be obtained, I want one. Cheers, Simon.

[Lurch]

On or around Fri, 04 Nov 2005 16:16:04 +0000, Alex mused:

That's answered that question then. Well done for trying, nice to see the special people are allowed access to computers as well.

[Dave Plowman (News)]

Get it fixed, then. The maximum temperature should be well below that - regardless of how low the flow.

[Jeff]

and to me , another reason for an electric shower is so you can still shower when your combi packs up

Regards Jeff

[Matt]

Probably, but then it sound like it is faulty. Water coming out of a shower many degrees above blood temperature can be painful.

Take your pick from any number

Because 99% of the posts will originate from Combi fascists (usually just one) who wouldn't know a good electric shower, nor a bad combi fed one, from a tin of baked beans. Hot water storage and a decent shower pump is the only sensible answer.

The mythical "qualities" of a combi boiler to raise a dribble of water by a number of degrees C so that the subsequent discharge doesn't freeze before the shower head. They don't exist outside the confines of a warped mind of a part time plumbing counter assistant.

[Peter]

Something of a rare device in the UK but I have a Stiebel Eltron DHE

1. Its a 27kW three phase electric water heater and a great shower heater.

[DMac]

Sounds interesting. I take it you've installed this in a house. How much did it cost you to get three-phase installed We had a quote for about £800 to run cables about 10m across a pavement , new meters etc for a lathe I wanted to get..

What is the flow rate like - how quick will it fill a bath?

And given the cost of having 3 phase installed - and the high price of electric surely it its more cost effective to use a modern gas boiler and heat store

Something like the Keston.would do your heating as well

DM

[meow2222]

if youve got gas CH, you can either add a HW tank or an electric heater, or buy an XL gas boiler. With the secondary leccy optione, youve got enough combined power input to get sensible HW with no storage. Why secondary electric? Cheaper than a huge gas boiler, and only used at peak demand times, ie baths and showers.

Havent costed it up, but it sounds like a possibly reasonable approach in principle. Secondary benefit is no loss of HW if either system goes down, just wont be as good heating temporarily.

NT

[Peter]

A standard bath filled deep is 10 minutes. Not so fast but tolerable. I am toying with the idea of automating this (flow rate sensor on cold inlet) so the bath will fill to a preset volume and then stop.

Yes, I would not recommend it as cost efficient, though after the

3-phase installation it is a low maintenance system. The duty cycle required of hot water supply for baths and showers is low so it doesn't add much to the overall energy bill.

I know, I plan to fit one for the central heating when I can figure how to route its flue. It will only have to be switched on in the cold months, in theory!