Instant electric water heater for shower and sink

[oldbutnotdead]

Okay thanks.
I'm surprised 9kw showers are only seen as tolerable or limited. I've never had any complaints with those I have used - including the one currently installed in my house.

They're OK UNTIL you experience a proper high volume shower (15 litres/minute) either from a pump setup or a good mains pressure setup. After that they feel a bit lame- OK in the summer (when ground temperatures are relatively high) but in the winter the flow rate dips massively. Well it does on mine (but it has just occured to me that the chancers who put the supply pipe in only buried it 6" below the path, if I bury it properly supply temperature will come up a bit)

 

[just pumps]

Really? Even with no storage vessel?

Opps, my error for failing to open the links.

 

[benwatkins]

I stumbled across this whilst looking for something else and thought I'd update it in case it's of benefit to someone else looking to do the same.

I installed an Ariston Aures 9.5kw in the end and haven't looked back. It's been faultless. The water here is (literally!) freezing at the moment and I'm still getting 3.5-4 L/minute. Perfectly adequate in my opinion. I use less than 40L per 10 minute shower instead of 150L. Not to mention the savings from only heating water when I need it.

The mixer valve was a bigger issue than I thought. Most are thermostatic now which is normally a good thing. The problem is that they adjust both hot and cold flow at the same time - so if the water is too hot they turn the hot flow down and cold flow up. Obviously, if you turn the hot flow down it makes the water hotter! I knew this before I started but I thought the mixer would sort it out. I found in practice that the temperature always gently fluctuates but never too hot and never too cold. I eventually switched to a manual mixer which solved the problem. If I did this again I'd be inclined to try a single hot water pipe with a single tap. The wider you open the tap the colder it gets. I'd obviously have to make sure the flow isn't restricted too much so the water runs cool with the tap wide open.

A flow restrictor is essential. Factory fitted flow restrictors/aerators on taps and shower heads are nowhere near restrictive enough. Open the tap wide and the water is stone cold. With a flow restrictor and a bit of patience it can be adjusted so that the water is always piping hot when the tap is wide open. Yes, if you want the temperature to always be the same you have to adjust the flow throughout the year to account for incoming water temperature but in practice I haven't had a problem with this. I think I've tweaked it two or three times in two years (one of those occasions was today!)

The heater has a minimum flow rate so you have to open the tap quite a way to get warm water - you can't have a trickle of warm water. And if you only open it just enough for the heater to cut in the chances are the flow will drop slightly and it will cut back out. So you basically get used to opening the tap wide every time and if it's just handwashing you find yourself watching gallons of water blasting down the drain whilst waiting for it to run hot. In practice I find I only use the hot water for showering and filling the sink.

Re warmup times I think it's about the same, possibly slightly quicker, than a gas combi. But as I mentioned above I think you waste more water because the flow is higher.

Overall it works fine. I didn't go down this route entirely out of choice - I don't have space for a tank and a combi boiler is impossible/impractical for a few reasons. I would recommend it to someone else in my position but you need to be prepared to understand the foibles.

 

[winston1]

Then I thought as the shower needs replacing why not replace it with a bigger instant hot water heater and use it to supply both the shower and bathroom sink?

Is this a stupid idea or am I on to something?

I have exactly that system in my garden room and it is perfect.

 

[Bohobee]

I stumbled across this whilst looking for something else and thought I'd update it in case it's of benefit to someone else looking to do the same.

I installed an Ariston Aures 9.5kw in the end and haven't looked back. It's been faultless. The water here is (literally!) freezing at the moment and I'm still getting 3.5-4 L/minute. Perfectly adequate in my opinion. I use less than 40L per 10 minute shower instead of 150L. Not to mention the savings from only heating water when I need it.

The mixer valve was a bigger issue than I thought. Most are thermostatic now which is normally a good thing. The problem is that they adjust both hot and cold flow at the same time - so if the water is too hot they turn the hot flow down and cold flow up. Obviously, if you turn the hot flow down it makes the water hotter! I knew this before I started but I thought the mixer would sort it out. I found in practice that the temperature always gently fluctuates but never too hot and never too cold. I eventually switched to a manual mixer which solved the problem. If I did this again I'd be inclined to try a single hot water pipe with a single tap. The wider you open the tap the colder it gets. I'd obviously have to make sure the flow isn't restricted too much so the water runs cool with the tap wide open.

A flow restrictor is essential. Factory fitted flow restrictors/aerators on taps and shower heads are nowhere near restrictive enough. Open the tap wide and the water is stone cold. With a flow restrictor and a bit of patience it can be adjusted so that the water is always piping hot when the tap is wide open. Yes, if you want the temperature to always be the same you have to adjust the flow throughout the year to account for incoming water temperature but in practice I haven't had a problem with this. I think I've tweaked it two or three times in two years (one of those occasions was today!)

The heater has a minimum flow rate so you have to open the tap quite a way to get warm water - you can't have a trickle of warm water. And if you only open it just enough for the heater to cut in the chances are the flow will drop slightly and it will cut back out. So you basically get used to opening the tap wide every time and if it's just handwashing you find yourself watching gallons of water blasting down the drain whilst waiting for it to run hot. In practice I find I only use the hot water for showering and filling the sink.

Re warmup times I think it's about the same, possibly slightly quicker, than a gas combi. But as I mentioned above I think you waste more water because the flow is higher.

Overall it works fine. I didn't go down this route entirely out of choice - I don't have space for a tank and a combi boiler is impossible/impractical for a few reasons. I would recommend it to someone else in my position but you need to be prepared to understand the foibles.

Hi @benwatkins - I've currently got a post on the go regarding this exact same thing!! I had actually seen your original post when researching but obviously hadn't followed it to the end as I've only just seen this update. So this is exactly what I want to do in my outbuilding - except feeding to 2 sinks as well as the shower (not anticipating ever needing to use more that one item at a time). The first thing I have already learned from my post answers is that If I want to do it I will need to switch the thermostatic mixer for manual .... so I am already prepared for that... can you just give me a bit more info on what a flow restrictor is please??
On the whole most of the replies I'm getting seem to think it won't work - like you were, I'm confused as can't understand why the instant heater is any different to an electric shower!
Only thing that maybe concerns me is that the shower I have bought is a double head shower.... potentially with the low flow rate this may be competely pointless as the top head may literally end up a trickle...
My other option is to install a storage type boiler. I do have the space for this - the bonus's would be that I wouldn't need to swap my thermostatic mixer out for a manual (saving £30) and would get a better flow rate, but the negatives are that it would cost approx £200 more for the boiler and I wouldn't have instant heat so would have no instant hot water for hand washing unless I turned it on everytime we went out there.
Given your experience what would you say?? should I stick with my original plan and go with it or spend the extra and forego the instant heat?
Also - honest comparison - does the electric boiler heated shower work as well as your previous electric shower or do you think an electric shower is actually better?
THanks!

 

[Bohobee]

I have exactly that system in my garden room and it is perfect.

Hi! how do you find the flow rate for the shower? and do you think it would work with a double headed shower?
THanks!