Electricity

**Missismiggins** · 05-09-2009, 08:32 PM

Any sparks out there can answer a question?

For instance, I have a 10KW water heater, it has 3 settings, 3KW, 6KW and 10KW.

Now, suppose I select 10KW, and the water is piping hot - i reduce the hot water flow by closing the hot water supply and increasing the cold water supply. Is it still running 10KW?

So, now the hot water at 10KW and is running at 50% (I turn on the mixer tap) flow rate 50%, and the cold water is running at 50% - am I using 10KW or 5KW - If I am using the full 10KW where does the extra power ...go? (I am looking at efficiency - whether it is better to set a shower to 6KW and be able to run two showers, or is it just wasting the electric?

Thanks

**daveboy** · 05-09-2009, 08:38 PM

Ask a plummer

**Thetyim** · 05-09-2009, 08:53 PM

I presume it is controlled by a thermostat.

It will be consuming 10KW all the time the thermostat has it turned on

**Missismiggins** · 05-09-2009, 08:55 PM

Its not a plumber I need just a spark! - besides, what equates to a plumber here? -someone capable of flushing the bog?

And a spark??? someone that can put a plug into a socket without frying himself?

**Missismiggins** · 05-09-2009, 09:02 PM

Originally Posted by Thetyim

I presume it is controlled by a thermostat.

It will be consuming 10KW all the time the thermostat has it turned on

Yes, Understand that but the 10KW light never goes off.

OK, lets go back a step - if the water is supplied by a mixer tap- the power is set as 10KW, I mix the water to get a warm mix ( about 50% load) what is happening with the electric?

Is the shower running at 10KW or not? and if it is running at 10KW - where is the excess heat being wasted?

There must be a bit of logic to this somewhere ! (There are no lights that dim or go off to indicate that 10KW is disengaged - so what happens to the excess heat?)

**woodenshoe** · 05-09-2009, 09:06 PM

The settings set the required power. NOT the waterflow. If less power is needed to heat as a result of reduced waterflow, the thing will most likely switch on/off one or all heating elements. So there is no "extra power" to go anywhere...

Most efficient is lowest temperature of the heater. (heat loss) But that will also give you the shortest shower time depending the water volume in the heater.

Any setting you pick will not waste energy, it will just make your heater heat up next batch of water slower or faster. Mind you 10 KW may require high Amps.

O, keep the temperature above 65 C.

**Thetyim** · 05-09-2009, 09:07 PM

On my shower at home the power light stays on all the time but the heating element is only being used when the thermostat turns it on

**Thetyim** · 05-09-2009, 09:09 PM

Originally Posted by woodenshoe

Most efficient is lowest temperature of the heater. (heat loss) But that will also give you the shortest shower time depending the water volume in the heater.

You are assuming a tank heater I was assuming an instant hot water shower.

Which is it MM ?

**woodenshoe** · 05-09-2009, 09:10 PM

"the 10KW light never goes off."

the light may be indicating power selection and not on/off...

**woodenshoe** · 05-09-2009, 09:12 PM

yes i do assume a tank heater...

10 KW flow thru? Never heard of it...

**Thetyim** · 05-09-2009, 09:21 PM

Originally Posted by woodenshoe

10 KW flow thru?

Triton T80XR 10.5KW

**dirtydog** · 05-09-2009, 09:25 PM

I've never heard of a 10kw shower heater, can't imagine it getting cold enough in Thailand to warrant that sort of power for a shower.

**woodenshoe** · 05-09-2009, 09:41 PM

ok, now i have..

**DrAndy** · 05-09-2009, 09:41 PM

Yes, Miggins. you are right

**woodenshoe** · 05-09-2009, 09:44 PM

in my book a 10.5 KW electric device would require 1 ph 220v 25 amp or 3ph 380v 16 amps. i run my entire home on that..

**lom** · 05-09-2009, 10:01 PM

Originally Posted by woodenshoe

in my book a 10.5 KW electric device would require 1 ph 220v 25 amp or 3ph 380v 16 amps.

10500/220 = 47.5 amps. One needs a 10 sqmm cable for that..

**Thetyim** · 05-09-2009, 10:34 PM

Originally Posted by woodenshoe

the light may be indicating power selection and not on/off...

Whatever sort of shower it is, I think this is the correct answer

**Missismiggins** · 06-09-2009, 03:37 AM

It's a direct flow heater - Panasonic 10XXX something - it is not really a shower as such, it is a "multi Point" water heater - and yes, you do not need 10KW for a shower - in fact it would probably cook me if I could bare to stay in the water on this setting.

The "heat" lights do not go off!, regardless of water flow - unless you slow the hot water flow to virtually a trickle, then the overheat cuts in. What I am trying to understand is - is it burning 10KW as long as the heaters are on?

For example - 100% hot water flow gives you for instance boiling water - using 10KW.

Then, I reduce the hot water flow by half - by switching the mixer tap to half hot and half cold (the flow rate doesn't change it's already at maximum) Where does the other half of the heat go? The machine still indicates that all three heaters are on - nothing switches off, so if it is still running at 10KW, with the same water flow, at half the temperature - where has the other 5KW gone? - or am I going mad? (I see no sign of a thermostat as this thing just gets hotter and hotter - the only thing that cuts it out is a severely reduced water flow)

**Missismiggins** · 06-09-2009, 03:48 AM

Originally Posted by lom

Originally Posted by woodenshoe

in my book a 10.5 KW electric device would require 1 ph 220v 25 amp or 3ph 380v 16 amps.

10500/220 = 47.5 amps. One needs a 10 sqmm cable for that..

If the cables from the mains are not securely tightened at the "SAFE T CUT Box" then they begin to melt and smoke, (I never run it at 10KW, the most is 6KW in the Winter).

The thing was we were a bit short of voltage here - until we got hooked up to the new supply - i.e. my main supply was about 216Volt, and if I switched the shower on at 10KW we were at 175Volt, so the water never actually got any hotter - the lights just got dimmer and all the computers and flourescent tubes would switch off.

Now, we have 232 Volts, and the 10KW actually works - it is enough to poach a small child.

**Loombucket** · 06-09-2009, 04:51 AM

Originally Posted by Missismiggins

is it burning 10KW as long as the heaters are on?

Probably, yes.

Originally Posted by Missismiggins

I see no sign of a thermostat

I should have thought that there would be one somewhere but I am not that well versed in Panasonic water heaters.

**lysander** · 06-09-2009, 06:00 AM

If you're using a mixer tap it's inserting cold water from your ordinary water supply into the heated water from your boiler. Your boiler is working at whatever wattage you set it at. It has no knowledge of the cold water that's being inserted into the water flow coming out of your shower/tap/brain

**Marmite the Dog** · 06-09-2009, 08:00 AM

Sounds like a bath heater rather than a shower heater.

**crippen** · 06-09-2009, 09:24 AM

A lot of water heaters now have full electronic control of the water temperature.A device in the output water measures the temp.electronically,and sends a signal to an electronic current regulator to keep the water at the heat setting required.Forget all the names of the bits now:- its been a long time---

**lom** · 06-09-2009, 09:33 AM

Originally Posted by crippen

Forget all the names of the bits now

Thyristor, triac

**crippen** · 06-09-2009, 09:34 AM

Thermo-couple !

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