Tankless instant electric water heater recommendation, no wet radiators

[babaisrock]

Hello friends, my immersion water heater is dying, and I'm looking for a tankless instant electric water heater. My main goal is to have unlimited hot water flow for the family, and to reclaim the space that the tank had took up in the boiler room.

My apartment only has electricity (single phase), and I don't have a wet radiator system, instead I have an electric air conditioner machine.

After extensive research and some plumbing consultation, I am convinced that my only option is a water heater (something like an electric shower), and currently looking at Stiebel Eltron DCE-X 10/12 Premium. While Stiebel Eltron claims that the DCE-X does not need a pressure release valve, a plumber told me I cannot install the DCE-X because my boiler room does not have an extra pipe for pressure release or overflow escape, leaving me super confused.

I wonder if a water heater is my only option, and whether or not installing a water heater requires an escape pipe or pressure release pipe? Any comments are much appreciated.

 

[ianmcd]

The Stiebel Eltron DCE-X 10/12 Premium does not require a pressure releif valve or assosciated pipe, that unit is just exactly the same as an electric shower, I wouldnt recommend it for what you require though

 

[big-all]

no expert at all but what you want is not possible with out capacity or storage you would probably need a 3 phase supply drawing a massive amount off energy so live with a large amount off hot water storage or spend possibly 10s of thousands upgrading your electrics

but purely a guess

 

[babaisrock]

Thanks both, why wouldn't you recommend the DCE-X or other electric showers? I understand that the flow rate may be slower, Stiebel Eltron says if I run it on 14.3kw settings, I can get a 7.5 liters per min, is that good enough for a shower?

Not sure if I really can get a 3 phase and no idea it will cost tens of thousands... originally I thought it would be something around 3000-5000. My apartment is inside a building with a lift.

 

[big-all]

i simply dont know but iff you look at average setups thats what is practical
iff you look at people with zero hot water storage and instant fairly unlimited hot water supply you will find there is a disproportionate cost for the set up you require so a more normal set up will tend to appear as the extra cost far exceeds the value of space you think you can save

 

[oldbutnotdead]

If you use the contents of your existing cylinder every day, your better investment might be in a new cylinder, larger if you have the room, fitted with a 2nd immersion heater for rapid recovery if you feel the need.
Tankless electric water heaters in a standard UK house are a massive compromise. Consider- a small gas combi boiler can deliver 20kw of instant heat- that's enough for a decent shower or will fill a bath in a reasonable time. Your electric thing can deliver 2/3rds of the power considered adequate for a decent shower. Not much of a selling point.

 

[stem]

7.5 litres / min should just about be ok for just a shower. You could try the shower you have now, run it for a minute collect the water and see how much you have. That would give you an idea.

There could be the risk that whilst showering another family member uses a hot tap elsewhere that steals most of the hot water flow. Where I have (albeit rarely) seen this type of heating device installed before, there has been one unit installed to supply the bathroom and another unit installed under the sink in the kitchen.

You don't mention a bath, but if you do have one I seem to think they hold about 200 litres, and at 7.5 litres / min that would take about half an hour to fill, and a washing up bowl would probably take somewhere between one to two minutes to fill.

The big benefit of a hot water cylinder with an immersion heater is that you have the option to heat it during the night using one of the off peak tariffs that provide half price electricity.

 

[ericmark]

As said, problem is speed, I have used a vented under sink water heater 7 litre 1 Kw which worked well, and not that big, in a caravan where I had limited space. The problem is filling a bath, with a 19 kW gas boiler it took around ½ hour, and the problem is we would forget it, and over fill the bath.

Most combi boilers look at 28 kW not for central heating but for the DHW, and 28 kW = 121 amp and supply is never over 100 amp, so can't do that with electric. at 12 kW that's 50 amp and many consumer units will not allow use of a RCBO or MCB over 45 amp, for a shower where the time used is limited you may get away with the slight overload, but to fill a bath no, so 10 kW for a 45 amp MCB, 9 kW for 40 amp, and 7.5 kW for 32 amp. As wanted for a long time, in real terms the 7.5 kW is the limit.

So 14.3 kW is 62 amp, over half the total supply to the home, and some consumer units will take a 63 amp RCBO, like Protek, but fusebox for example only goes to 50 amp RCBO's. As you go for the consumer units which will take 63 amp you also see the price rise for the SPD, and other components, so looking at a lot of money.

I am an electrician not a plumber, but to get enough hot water to fill a bath in a reasonable time with an instant heat device your looking at gas or oil, and even oil since it will not modulate very well it will likely have a small reservoir inside, unless gas is banned where you live, then LPG is likely an option.

I have never really looked into batteries, with the advent of electric vehicles the same technology can be now used to store power, but what the difference in storing power as chemical in a battery or as hot water, you are still storing the energy.

As to storing outside of the house, that may be an option, as I hunted for a new house, I found many with the oil/solid fuel boiler outside, so in a suitably insulated box outside with lagged trace heated pipes, no reason why the storage tank can't be outside. I note in warmer countries it is common to have the air conditioning unit hanging out of a window or wall. I have noted in the UK often a large lump of the heat pump is outside, on the wall or roof, so that could be an option, move the storage tank outside?

 

[flameport]

my immersion water heater is dying,

Have it repaired or replaced.

tankless instant electric water heater.

The worst possible choice. Massive power requirements to deliver a pathetic trickle of hot water.

Stiebel Eltron says if I run it on 14.3kw settings, I can get a 7.5 liters per min, is that good enough for a shower?

Not going to happen, that's a 60A load just for the heater. Many properties have a 60A supply for everything.
Installing a gigantic load like that on a domestic supply also requires DNO approval which you are unlikely to get.
Upgrading the supply won't be happening either.

That 7.5 l/min is for a temperature rise of about 27C, which at absolute best with incoming water at 10C, gives you a flow temperature of only 37C. In the winter it will be lower.