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Heating bath water electrically...possible ??
NigeEss - 19/6/12 at 08:52 AM

Customer of mine has a very large house and at the very far end is a guest room with an ensuite.
The bathroom used to be supplied by it's own gas boiler which is still there but disconnected. The
gas was cut off during an extension build and hot water is now fed from the main house but as
the boiler is so far away there's nearly half a bathful before there's warm water coming through.

He's asked me to arrange an electric system instead but from what I can gather these all use a
tank, but he doesn't want that.

Other option is to re-jet the boiler and run it from a tank, which he's not too keen on.

Ant ideas from the forum that knows everything ?

scootz - 19/6/12 at 08:56 AM

Toprivetguns - 19/6/12 at 08:57 AM

Can you have a set-up similar to those electric showers ?

bartonp - 19/6/12 at 09:04 AM

Unvented electric water heater 10-12kW should do the trick:

http://www.cnmonline.co.uk/Hyco-Instantaneous-Inline-Water-Heater-pr-30698.html

Editted to say it will be slow, when you think the avg combi puts 25kW into the water....

[Edited on 19/6/12 by bartonp]

twybrow - 19/6/12 at 09:05 AM

But bloody slow to fill a bath with...

daviep - 19/6/12 at 09:18 AM

There is no easy answer, you could use something like Redring-Powerstream-Unvented-Instantaneous-Water -Heater
but you will need to run a new 10mm2 supply which is a pain.

OR

Something like Zip-Aquapoint-lll-Unvented-Water-Heater-100-Litres which you wouldn't need a seperate supply but it isn't small.

Davie

[Edited on 19/6/12 by daviep]

matt_gsxr - 19/6/12 at 09:24 AM

100 litres of water requires 420 kJoules to heat it 1 degree.

If the incoming water is at 10 and bath is at 35, then that is 25degree increase.

So, 25 * 420 = 10500 kJ

1kJ = 1kW * 1second.

So, 10500 kJ = 10500 kW * seconds.

so at 10kW this will take 1050 second (or 29minutes).


I was just interested.

owelly - 19/6/12 at 09:25 AM

Can you run a return for the hot water circuit? A microbore from the bath back to the boiler or main hot water circuit. With a bit of clever design you could probably get away without a pump.

Daddylonglegs - 19/6/12 at 10:15 AM

Saw a film once where the guy must have been trying to do the same.....

....he plopped a plugged-in toaster into the bath for his darling missus! Don't think it worked though

[Edited on 19/6/12 by Daddylonglegs]

NigeEss - 19/6/12 at 10:24 AM

quote:
Originally posted by scootz


Perfect

Matt-gsxr, your calcs indicate anything that heats on demand, that would include electric shower type device
would be far too slow for the bath side of things.
Running anything back to the new boiler system is a non starter, too far, solid floor in the extension and he
does not want cables etc on show.

However, DavieP may have the answer. There is no prob running a big cable as the en-suite in question is
in the old part of the house which has suspended floor deep enough to crawl through and the main meter is
there too. Which is why the electric option is being pursued.

I knew the collective would have the answer

Mr Whippy - 19/6/12 at 11:22 AM

My house is all electric heating, the bath has its own hot water tank large enough for the bath volume, I also have a much smaller heated tank for the sink etc that is very well insulated. It can take almost an hour though to heat the bath water up and I have a long immersion heater element to do that, I think instant heat is impractical due to the sheer power required. One alternative which I have tried myself is to have some solar panels (mine are home made using black painted radiators in glass and wooden boxes on the ground) heating bath water tank to boost the normal water temperature in the tank so the only needs to heated it a bit more, however unless the sun is actully shining you get zero extra heat.

Irony - 19/6/12 at 11:38 AM

When I installed my own electric shower I had to put in new cables and I think my shower is 12KW (Mira Sport Max). When the shower comes on at full power you can see the house lights flicker. It would take a age to fill a bath though.....

bobinspain - 19/6/12 at 02:13 PM

Lateral thinking:

1. Only put mucky guests in that room, so no shower req'd, (teenagers I'm thinking of here).

2. Tell the renters of the 'problem room' that if they want a bath they need to chat up one of the other guests and borrow their bathroom.

3. Advertise it as a trendy 'Nordic bathroom' with cold plunge pool and bang a second hand sauna in there.

rodgling - 19/6/12 at 04:01 PM

Whilst his hot water was not working, a friend once disassembled a kettle and dangled the element in the bath, then turned it on (while he was not in the bath). Fortunately this just tripped a breaker and no one was killed...

So don't try that.

[Edited on 19/6/12 by rodgling]

kenton - 19/6/12 at 04:56 PM

Tape an electric heater trace cable to the pipe and cover with pipe lagging. Thats what we have done, recomended by the plumber, standard practice he said.
Kenton

owelly - 19/6/12 at 05:04 PM

Standard practice to stop freezing perhaps but I don't think trace heating is there to heat the contents of the pipe to bath temperature!

Ninehigh - 19/6/12 at 06:37 PM

I've seen some "instant hot water" taps for kitchen sinks, don't think it would be good enough for a bath though.

Maybe an extra option would be to turn it into a jacuzzi, and have the vaguely warm water circulate around the bath with some extra heating in there (so it would be gas and electric, each doing half a job)
Actually while I think of it plumb the hot tap into an electric shower unit, so the unit near the bath is just finishing the job, as it were