3 phase installation for power shower

[mickbristol]

Hi all,
I describe my plans, but i could be really wrong so please stop and advise me...
i live in a bungalow and got a standard electrical shower which i would love to change to a power shower.

i dont have any gas and got an old vented boiler installed, so i was looking for an instantaneous instant electric water heater as i wouldnt like to heat a full boiler for just a shower/tap, as the heating is electric..
i found very good ones from Stiebel Eltron, but they require a 3 phase 400v. which i am not sure i have.
first question, how to find out ? i got access to my meter and electric box but not 100% sure how to identify it...
if i dont have it, then what could be the cost to buy a single phase to 3 phase inverter? i had a rough idea on ebay, and to deliver up to 27kW to the Stiebel instant boiler...it would cost me ... 2 000 pounds !! ???

i am not looking to spend 200 pounds in total as i know it will be more expensive than that. but am i looking for something out of my league ? should i give up the idea of a power shower with instantaneous heating ?

thanks for your help

 

[Brightspark2]

You dont need a 3phase water heater!!! lol


If you dont want an electric boiler, you could get an electric power shower and a water heater for the tap you only need a small one though, nothing industrial size...

 

[mickbristol]

hiya, thanks for your reply
yes i have already installed a small undersink boiler as the pressure for the hot water was too low, so i could do the same for the other tap in the bathroom.
but the electrical shower i have is taking 10k and the water flow is nowhere near a power shower, so i thought i had to get around 15kW at least to have a power shower.

have you got any sugestions for power electrical shower ? which flow rate, what pressure ?

thanks again

 

[Deleted member 26818]

There are some instantaneous water heaters, that are supposedly designed for two-three sinks or one sink and a shower.
Redring is one company that springs to mind.

 

[kingeri]

Don't go installing anything, you're not qualified! Your supply and main fuse need checking to see if they can handle a 15kW appliance. Get an electrician in! (please)

 

[UNG]

Do you have low mains water pressure, if you are looking for a more powerful shower then you would need a cold header tank and a shower pump to supply the water pressure needed for your existing 10kw shower

 

[mickbristol]

oh yes dont worry i will get a professional to install this. i have done an undersink boiler as it was only from a 13 amps socket wiring.
other problem i have with electrical shower is that they look "cheap" in yout shower, i would rather have something which looks like a normal shower... lol
i am giving up the idea of a 3 phase, i have seen my mains supply and can see only 2 big cable so...

so you think 10kw would be enough to heat water at 7 or 8 liters per minute ? mmm sounds a bit just for me, but im not expert at all

 

[mickbristol]

the pressure is around 6 bars, as i had to fit a High pressure relief for my undersink boiler, i think that shoudl be more than enough?
im new owner of this house and the old ones said the electric shower is not very old... but sure there must be something better on the market for 10kw ?
what kind of flow shall i expect for 10kw for let's say heating from 15 degC to 35 ?

 

[UNG]

Sounds to me that the shower is faulty what make is it

 

[mickbristol]

it's a mira zest
just done a few measurments, i have 4 liters per minutes heated from 15 to 35 deg C for 9.3kW
...

does it sounds ok ?

 

[BroadReach]

Hi

4l/min = .07l/s which with a 20 deg C rise would be about 5.8kW. Sounds like the heater is up the chute.

Or another way 4l/min with 9.3kW should give a delta T of about 32 deg C

 

[mickbristol]

oh i see, i dint know the formula...
i shall have a look at the shower heater then, is there any particular maintenance to do ?
thanks very much

 

[BroadReach]

The formula is:

kW = water volume (m3/sec) x density of water (kg/m3) x specific heat capacity of water (kJ/kg K) x Delta T (K)

Density of water is 1000kg/m3 and specific heat capacity of water is about 4.1813kJ/kg K

Better and easier to clamp the supply cable.

Better still get a sparky in?

 

[mickbristol]

i got it,
so for the same temp rise of 20 degC, if i buy this Redring 12Kw instantaneous water heater, it should give me about 8.6 liter/minutes ... that should be ok for a power shower ?
i would have thought the heating transfer from the resistive load to the water depended a lot about the conductive surface between those 2 ?

 

[Knobhead]

Thanks for the formula. Another one to add to the library.