Electric shower heater mechanism for sale?

[ocset]

Hi
I’ve searched the web for offtheshelf electric shower  water heater coils but cant find one. Do you know of any I can buy?
I wish to re-make my  electric shower so that I can keep the flow rate the same and yet adjust the water temperature….so I need to be able to pwm the heater electric current, so that  heater power can be finely adjusted rather than just have three fixed power  settings like it does now.
I would also like to try simply using a current regulator to  finely reduce the heater  current.
Do you know where I can buy an electric shower water heater thingy?

[Gyro]

You would probably be well advised not to tamper with the internals of an electric shower. It doesn't sound as if it would end well with regard to human life - your own or others in your household, or the validity of your house insurance.

There isn't usually an issue with finding spare parts for main brand showers on the web though.

[ocset]

Thanks, ive searched the web widely, but i cant find  out how the electric showers sense the water temperature.... ie,  do they have a thermistor in the water flow itself, and somehow get wires to it, or do they sense the water temperature by simply sensing the temperature of the outer case of the element?
Also, is the element just a small water tank with a heating element in it....or is the element a tube of hollow , heated metal through which the water flows so as to get heated up?
These  things i cannot find on the web..please assist?

[Gyro]

It's a simple constant output heater (normally with two elements for two power levels) running 100% duty. The way they vary the temperature is to vary the flow rate, as you indicated in your OP.

The only sensors are safety ones for minimum water flow/pressure and/or an overheat thermostat. They are almost certainly electromechanical.

If you try to keep the flow rate constant and PWM the heater then you are always going to end up with less flow rate capability for the same temperature than you have at the moment. EDIT: The control knob is also a water valve rather than a pot too.

As I said previously, trying to mess with the electrics and add electronics ito a relatively primitive (not well sealed) water and naked human exposed appliance like this is dodgy as hell.

[MosherIV]

You will probably have to use Triacs to control the power. Basically a light dimmer for electric shower. The problem you are going to face is that >1KWatt is going to cause so much conducted noise by switch large current on/off that it will cause other electronic equipement huge problems.

Oh and did Gyro mention that it is incredibly dangerous mixing electricity, water and humans!?!

[Gyro]

More like 8 - 10kW from a quick look at Screwfix. It takes an awful lot of power to flash heat flowing cold water! 

PS. Oh and did I mention that it is incredibly dangerous mixing electricity, water and humans!?!  I think I might have!

[mariush]

maybe these help

[SteveyG]

You would probably be well advised not to tamper with the internals of an electric shower. It doesn't sound as if it would end well with regard to human life - your own or others in your household, or the validity of your house insurance.

You'd do well to cause a serious danger - the boiler unit and outlet are tied to the CPC. Most shower circuits should be covered by an RCD of some description by now too.

If you want to do this, I would not advise trying to switch mid-cycle. Just employ valley switching and cycle skipping to adjust the output power. Bear in mind that if you keep the flow rate at maxmium, the shower will never be able to get hotter than the coldest setting with both elements turned on.

[ocset]

https://www.youtube.com/watch?v=jiErqUkw690&feature=youtu.be
...thanks for this video...in this video, the author  gets under a shower which is no  more than  a resistive wire heater across live and neutral, which is in a water pipe which sprays directly on the shower user........he even holds an earthed bit of metal, but still he is not electrocuted. He does this having disconnected the earth from the incoming mains cable.
Even when he puts his hand right under the shower head, he is getting a shock but mild enough for him to be able to keep his hand there....it shows that the resistance of water is quite considerable.

If the water would have had  high mineral content, i suspect the chap may  not have survived, tragically.

it does beq the question...in a "normal" shower, the heating element is obviously directly connected to live mains......and the  water must flow over the conductive element....so effectively the shower water is connecting the shower user to live mains? Is there any insulation layer there...i doubt it....i believe that showers just rely on the fact that users will have an RCD installed and also rely on the high resistance of water to avoid electrocution.

[IanB]

Do you know where I can buy an electric shower water heater thingy?

They are commonly found inside electric showers. So an electric shower would be a promising place to start looking for one.

Thanks, ive searched the web widely, but i cant find  out how the electric showers sense the water temperature.... ie,  do they have a thermistor in the water flow itself, and somehow get wires to it, or do they sense the water temperature by simply sensing the temperature of the outer case of the element?

A good way to find out how things work is to get a sample of the thing and look inside it. Everyone else in this thread with knowledge of how such showers work probably got that knowledge by looking inside one of them. They are very modular, with a few components arranged inside the outer housing. It's not hard to figure out the operating principles.

[LeonR]

Electric showers use elements like these:





There's a lever to switch between "warm" and "hot" that controls the current between a single segment and the whole element (there's also "cold", which just disengages the element). There's not a lot into it aside from basic physics and electrical application - no sensors, etc.

They are very common in my country (I'd say at least 50+ million people use them on a daily basis, considering the number of houses that use gas heaters) and lethal accidents with them are very rare occurences.

If you're testing one of those make sure you meet the basic requirements - 10mm cable for live/neutral and a suitable breaker. Power usage tends to run into 5000~8000W depending on the model.

There are also "electronic" models with finer temps adjustments but I've yet to take a look what's inside them.

I suggest you use the search terms "chuveiro lorenzetti" (chuveiro = shower, Lorenzetti = a reputable shower/electric stuff brand here) if you want to get into more detail.

They even have an english site: http://www.lorenzetti.com.br/en/

Another brand: https://hydra-corona.com.br/

Found someone selling them into ebay:

https://www.ebay.com/itm/LORENZETTI-RESISTANCE-SPARE-ELEMENT-PART-Jet-Set-Maxi-220-v-4400-w/283567169978

[Jeroen3]

If it isn't for showering, just get a tankless water heaters and thermostatic mixing valve.
Also for showering it's nice, but it requires hot and cold pipe at the shower.

[DenzilPenberthy]

This seems like a very bad idea from a safety point of view. And an absolute nightmare for EMC!

It also seems a bit dodgy from a conceptual point of view.  You can vary the shower from tepid to scalding by controlling the flow rate from waterfall to trickle.  Your options are on a spectrum from tepid waterfall to scalding dribble.  I get that it's a bit annoying to work that way but if you change to continuous flow rate and variable temperature then this is going to leave you much worse off.

Your heater won't be capable of producing any more power than before. It will only be capable of running at reduced power.  That means your flow rate will have to be fixed at dribble, while your temperature will be adjustable from tepid to scalding.  So your options will be on a spectrum from tepid dribble to scalding dribble.  This is worse than the original setup. No one wants a dribbly shower.

Your other option is go for a high fixed flow rate which leaves your options even worse: on a spectrum from tepid waterfall at best to icy cold waterfall at worst!


If you're embarking on this project because you want super hot water at high flow rate, this won't be possible.

[SiliconWizard]

[ocset]

Thanks,
All the electric showers that i've ever used have about three fixed temperature settings,
and then as you discuss, the fine adjustment in temperature is made by adjusting the flow rate.
However, if one inadvertently reduces the flow too much, then the water gets scalding and the
high temperature cut-out acts, and you end up getting freezing cold water spewing all
over you. Its easy to reduce the flow rate too much like this, because of the long-time
thermal time constant of the overall  system....so really, fine adjusting the temperature by adjusting the
flow rate is not a good way.
I have a "Aqualisa Vitalise S " shower at the moment, and the flow rate adjustor has broken, so instead of fixing
it, i  want to modify the  whole thing.
Strangely, with my fixed flow rate, funny things happen when i adjust between temperature setting 1 and 2....
(1 is colder than 2). When i go from 2 to 1, then at first, for some reason,  the temperature goes scalding hot, and then the temperature
gets to temperature setting 1.
I have lived in about 20 different flats over the last 15 years, and this kind of shenanigans, with whatever electric
shower has been installed, is very usual.


And regarding all the above great videos, i wouldnt mind betting that all electric showers are simply a stream of water flowing over a bare wire connected to live mains, which then gushes this water over the user.....its obviously safe, as the above showers are used by 50 Million people  as Leon kindly says....even if there is no earth connection, its still safe...look at the  above videos where they are just incapable of killing themselves....it appears that water isnt as conductive as many think it is.
Not having insulation over the heater wire, obviously makes it more efficient...more energy saving....water flows over live mains, then over the human body, as in the above videos. He even removes the earth wire from the shower, and then directly connects himself to an earthed metal plate, and then gets under the shower, and he is not electrocuted.

---------------------------------
I would put forward that some parts of this video  need  more clarification…
https://www.youtube.com/watch?v=jiErqUkw690&feature=youtu.be

….This is because, in the bit where he  earths himself and steps under a shower that is not earthed , (and the shower  is  just a stream of water across a bare live mains conductor)…….the resistance of his “earth” connection,  to the “earth” at the   relevant substation transformer, is not known….we need to know this resistance in order to evaluate this video…sadly, this data is not provided.
I mean, for all we know, he could be in a  very dry country where the soil  is clay, and even though he is connected to the “earth” soil at his house, this soil may not be well connected to the “earth” soil at the relevant substation transformer.
Maybe he would have so very tragically died if he had been in a country where its low and wet, and the earth is like a very low resistance connection back to the substation transformer.

Do you agree?

[LeonR]

@treez, I just forgot to add that I was talking about the simplest models (that curiously they tend to be the more reliable... one of the "if it works, don't bother trying to fix" cases?).

There are some models that work with finer temp control, just like the ones the OP seem to learn more about. I found out Lorenzetti have a series (Ultra) that seem to fit your needs... although I found out about it on a video where something went bad enough to blow a hole on the PCB and carbonize a good amount of the internal components