On demand heater problem

[VerityP]

Hi, thanks for reading this, hope you can help!

Basically we've had a bit of a nightmare with the plumber we chose and have had to rip out all the work he did because he used the wrong pipes etc.

We now think he may have given us the wrong info about the hot water heater he was going to fit as well.

We asked for an on demand water heater instead of a boiler because we live in a one bed flat (in which we are re-doing all the plumbing) and only have an electric shower and no bath. So we only need hot water supplied to the kitchen and bathroom taps to wash up and wash hands.

The plumber told us he would by the heater and that it would draw 3kw. We have had a 3kw feed fitted as we are also re-doing the electrics. It has now been rendered and plastered over completely a couple of weeks ago.

The problem is that my boyfriend and I have looked online and can't find an on demand heater with such a low feed - we can only find what seem to be mini boilers which hold about 20 litres and have a heat up time of about 7 mins. That's not what we actually wanted and we're really worried because if we have to rewire to allow 9 or 10kw we have to rip out loads of the plastering etc.

Is there any way to overcome this?

Thanks in advance,

V

 

[Agile]

There may be an on demand electric heater ( I have not heard of one ) or it might be possible to use an electric shower however those are all about 10 kW.

There are only two kinds of 3 kW heater, a 15 litre under sink unit and a little over sink that gives a dribble of hot water.

It seems that you have employed a plumber who was unable to understand what you wanted. Now you have to sort it out as best you can.

Tony

 

[VerityP]

That's what I was worried about. But doesn't fifteen litres storage mean it's going to have to be on, heating water all day, just so people can wash their hands when they want? Isn't that going to be really energy inefficient?

 

[Agile]

It only heats the water until its hot!

Sure there is a small heat loss but probably less than one kWH per day.

Tony

 

[nickthesafe]

You say he wired up for 3Kw, what size twin & earth cable was fitted?, is there any scope to go up to 4.2Kw?. you may have already seen these.....

http://www.tanklesswaterheater.com/products1.php

 

[Agile]

I dont believe those specs!

A 24 kW combi gives 9 li/min.

A 1/6 of that or 4 kW will therefore give 1.5 li/min yet they claim 1 ( US ) gallon which is about 4 li/min.

Even a 2.5 mm² cable buried in plaster cannot give 4.2 amp.

Tony

 

[simond]

Agreed.

A closer look at the specs will reveal that they do not specify the input water temperature or state that it is 'temperature rise' they are measuring.

 

[nickthesafe]

Looks pretty neato...if it works, has anyone thought of contacting them for detailed specs, temp rise etc??.

 

[Agile]

I would trust the laws of physics and not waste my time!

Tony