Electric and gas shower?

[Mark Hewitt]

Having installed a combi boiler recently we no longer have the backup of the immersion heater in the cylinder. So we are thinking about installing an electric shower so that at least that will continue to work should the boiler not be working for any reason.

However since we are having to modify the bathroom to take the new shower I would like to make regular use of it, not just in emergencies, it would probably be best in that case for the shower to be able to run off the hot water supplied by the boiler.. but should hot water not be available it should be able to generate its own.

Is there such as thing as an electric shower which can use a hot water input when it's available?

Cheers

[Ed Sirett]

I may be wrong but the simplest way would be to install a normal thermostatic mixer over the bath or in a cubicle.

The cost of an electric shower is nearly all in the supply installation. I would install the backup electric shower near the 'normal' one but remove the outlet hose. When needed you move the hose from the mixer to the electric unit until the boiler is fixed, keeping the same shower head and riser rail.

[Christian McArdle]

Well, you could run the outlet of a flush mounted thermostatic mixer through one, but why would you?

Electric showers are ugly and seriously constrain the water flow.

If you really need a backup, consider using an inline electric water heater on the hot feed to a standard thermostatic mixer shower setup. This way you get nice looks, good combi performance and can just switch on the electric (and turn down the flow) when required. Careful choice of location should enable all the taps in the bathroom to benefit. You could even drive the kitchen off it, although I wouldn't advise it unless the bathroom and kitchen are close together, or you'll be waiting an age for the water to come through. Select a good thermostatic mixer that claims compatibility with combis, as these should be able to cope with the effect of varying temperature on the hot side.

could probably get away with the cheaper 7kW, as it is only an emergency backup. You won't mind the slighter drizzle if it is saving you from having to use the showers down the local swimming pool! On the other hand, if you're running new cable and 30 quid means nothing to you, go for the full

9.5kW.

Have an electric shower head available. These will work better on the low flow electric situation than a standard power shower head that you should use when on combi power.

Christian.

[IMM]

It is best to install a normal pressure balanced mixer for the shower fed from the combi. In the hot water line have an in-line instant electric water heater for backup. The hot water from the combi just runs through the heater. It will give a dribble of a shower in comparison, but get you wet and clean when the combi is down, which should not be very long.

You can pick up the in-line heater for around £80-100.

[Mark Hewitt]

> You could probably get away with the cheaper 7kW, as it is only an > emergency

Now that's interesting! So this can be used to provide hot water to any destination when the boiler is not functioning? Presumably such an arrangement can be used to fill a bath should the boiler fail?

In that case I might look at something like this, at present we only have a bath and installing a shower is going to take several hundred pounds worth of plastering and tiling work to get it fitted. If we can do without that, all the better. Even if it's going to take half an hour to fill the bath that's better than having no hot water at all.

The 9.5kW is just over £100, which is much less than we were looking at for a shower installation. I take it my central heating installer should be able to source and fit one of these units?

[Christian McArdle]

At 9.5kW, the bath will have gone cold before it has finished filling! You can get 24kW inline heaters, which have the same output as a small combi, but you'll need more than a single phase supply. They come in single phase

100A versions (which obviously need a phase to themselves) and 3 phase 33A versions (which take a nibble out of each). Such a device could fill a bath.

It would take about 45 minutes, if it stays hot enough.

Christian.

[Seri]

Out of curiousity, could you use on of these inline heaters to provide a tiny bit more oomph to a shower that runs from an existing combi hot feed? I'm presuming this wouldn't work as the inline would restrict the water flow too much but I'd be interested to find out.

Thanks

Seri

[Christian McArdle]

My guess is that the inline wouldn't actually produce significant pressure difference and could be left in line and would work as you indicate. I have no data to back this up, though.

However, even a diddy 24kW combi should have enough for all but the most powerful showers, such as panel types.

Christian.

[Mark Hewitt]

Ah bugger.. sounded like a good idea.. back to the drawing board :-(

[Seri]

Well, it's not a panel shower that I've been looking at but I am thinking about installing some body jets. I wanted to feed 6 body jets plus the shower head so I was wondering about ways of adding a bit more oomph. That said, the boiler I have at the moment is a Worcester Bosch Greenstar HE40+ and it's spec'd for 16 liters a minute so I don't know if I would actually need more hot or not...

Maybe something I'll ponder a bit more.

[John Stumbles]

I think you can get an electric in-line water heater. I haven't checked but presumably it will let water flow if no power is applied. If not a valve or 2 is all that's required.