Electric water heating

lstar337

Smiley_Dan wrote: »

If it's just for a basin can't you just use one of those small hand wash units like http://www.plumbworld.co.uk/triton-t30i-hand-wash-unit-3kw-576-21962 ?

For hotter water such as instant boiling water you need a buffer under the sink.

Those are absolutely useless. Water just dribbles out of them and even then it is only warm.

We ripped them all out of our work building. It would take about 15 mins to fill a basin with water and it would be cold too as the porcelain sucks the heat out faster than the pathetic unit can supply.

Total waste of money.

Smiley_Dan

Richie-from-the-Boro wrote: »

The standing heat loss of a Part L - E7 water cylinder [how effectively it can store energy per insulation] was very good even before the 2010 regs changes. A standing loss per 24 hour cycle of about 2.5kWh even on a big 150 litre domestic tank.

[...]

It's my understanding that those regs apply to a theoretical cylinder with no inputs, no outputs, and filled with the water at the target temp.

In such a theoretical cylinder I would hope those figures would be easily achieved.

Pipes add an enormous amount of heat loss. So does mixing of water, when stratification is otherwise sought in the heating period.

Correct me if I'm wrong.

Smiley_Dan

lstar337 wrote: »

Those are absolutely useless. Water just dribbles out of them and even then it is only warm.

We ripped them all out of our work building. It would take about 15 mins to fill a basin with water and it would be cold too as the porcelain sucks the heat out faster than the pathetic unit can supply.

Total waste of money.

Ok, I haven't used them. We actually have one in our garage but I've never bothered turning it on

lstar337

Smiley_Dan wrote: »

Ok, I haven't used them. We actually have one in our garage but I've never bothered turning it on

Lol, don't bother.

They are one of those things that does such a pathetic job, you wonder why the manufacturer even bothered to mass produce them!

They are totally laughable, literally in our office they were a running joke!

Not so many laughs now we had them removed.:(

amtrakuk

If its for one skink then I'd suggest an under skink water heater like

http://www.tlc-direct.co.uk/Products/SOAP3slash10.html?source=shopping.com

They sit in the cupboard under the sink and and have a 10 litres of hot water ready to use.

Smiley_Dan

lstar337 wrote: »

Lol, don't bother.
...

Does raise the question though... if they were sized like a shower, saw 12kW, wouldn't that work fine on the grounds a shower certainly provides hot enough water, at a reasonable, if not surging, speed? Is it a question of space?

amtrakuk

Smiley_Dan wrote: »

Does raise the question though... if they were sized like a shower, saw 12kW, wouldn't that work fine on the grounds a shower certainly provides hot enough water, at a reasonable, if not surging, speed? Is it a question of space?

I have had first hand experience of these and believe you me their is better options out there.

I had 1 x (http://www.redring.co.uk/powerstream-12kw-water-heater-1990-current-spares.html)

I though 12 kW was ample for a whole house solution with the same train of thought as yourself - a shower is 9 so 12 would be ample.

Picture this;

My water heater Is still in the cupboard (disconnected) next to the kitchen sink, (2 meters) of pipe - When I was using it the water came out only 20c higher than the cold with the tap fully open

My bathroom above (7 meters of pipe) the water came out 13 degrees higher when fully open than the cold. Meant a luke warm shower.

These instant/on demand water heaters are designed to be used very close to the point of use AND designed for the hot taps to have a spray nozzle (like a mini shower head) to restrict the flow.

As they are designed for a "slow" rate of flow - basically a hand wash, the heat in the water is lost rapidly if the hot water has to travel though pipes any distance - its a catch 22.

If I cranked down the taps then yes I would get a high temp but the flow rate was about 1-1.5 litres a minute. Took about 10 minutes to fill a sink and then would have lost most its heat by the time it was full

My old combi boiler I think was rated at about 30kW for a reason.

I asked the sparky if I could use 2 x 12 kW in series but unfortunately 12kW (50 Amp) is the maximum a single phase domestic supply can safely supply. If you want to go higher I was told I will need to convert to a 3 phase supply (unrealistic)

From experience if you want a reliable sink full of hot water for hand washing or filling a bucket for mopping a "Stored water" solution is the answer. I chose a 210 litre Thermal store but you can get under sink 10 litre water heaters.

Richie-from-the-Boro

Smiley_Dan wrote: »

It's my understanding that those regs apply to a theoretical cylinder with no inputs, no outputs, and filled with the water at the target temp.

In such a theoretical cylinder I would hope those figures would be easily achieved.

Pipes add an enormous amount of heat loss. So does mixing of water, when stratification is otherwise sought in the heating period.

Correct me if I'm wrong.

- I'm not interested in that debate Smiley Dan, the figures I gave are about right [ish] for this debate
- this MSE is about ordinary people ordinary dwellings and ordinary problems
- once you get into heat loss from a surface as a function of BTU/hr/ft lost to surface temperature
- most people eyes would glaze over ........ and its a sterile debate anyway, all dwellings are different

All we can do in a forum is give a well intended and practicable opinion - the O/P is gonna do what they're gonna do anyway, everyone makes loads of wonka out of the 'mother' especially the plumber with a bonus of a hundredweight of redundant copper pipe and water cylinder.

Smiley_Dan

- this MSE is about ordinary people ordinary dwellings and ordinary problems
- once you get into heat loss from a surface as a function of BTU/hr/ft lost to surface temperature
- most people eyes would glaze over ........ and its a sterile debate anyway, all dwellings are different

All of these points are exactly why I raised my point.

AFAIK building regs in this regard are partly academic. Real life very different.

matelodave

If all she wants is a couple of pints of hot water then it's easier & cheaper to boil a kettle when required rather than replumbing and rewiring.
You don't need hot water just to rinse your hands - cold water is just as effective.