Hot water boost on immersion tank

DFB-D

I have no idea if such a thing exists but I am looking for a electric shower or instant hot water unit to work in conjunction with a water tank with immersion/ hopefully solar inputs.

I can find instant hot water units for sinks but none for showers.

The alternative is a electric shower with hot/cold feeds and heating, again I cannot find anything.

kirk.

Instantaneous electric shower is as good as anything

Don't fully understand the question?

Hot water is either instantaneous or stored

DFB-D

https://www.boards.ie/discussion/comment/119890170#Comment_119890170

Say for example a electric shower uses 9kwh to run with feed tempature of 5 degrees.

If I can use solar or have other feeds already heated and want to utilise by showering, maybe I can supply this to the shower at 50 degrees, reducing the kwh for the shower to e.g. 3 kwh.

Obviously, this already heated water may not be sufficient for the length of shower or be hot enough to generate the required temperature. Hence I am looking to include an instant boost.

Problem is, electric showers are cold feed only.

Sleeper12

I think you are trying to fix a problem that doesn't exist. If you have water heated by solar but it's not quite hot enough then it will only take a few minutes to top up the temperature via the immersion, gas or oil.

To pass safely standards you would have to be able to guarantee that the water temperature will not exceed X degrees before you start heating the water. This would mean the instant heater will be only able to function in limited circumstances. You could build in the option of mixing in cold water if the water is too hot but now you are talking about a hot & cold feed shower.

I can't imagine anyone selling something so specialised that they would only sell a handful per year. Because it would be such a specialised item the retail price could be three or four times the cost of a mass produced electric shower. Obviously it will be far cheaper just to run the immersion, gas or oil for a few minutes to bring up the water temperature in the cylinder

DFB-D

https://www.boards.ie/discussion/comment/119891253#Comment_119891253

Hmm thanks for the comments, but I think for my use case, use of the immersion wouldn't be cheaper than the electric shower. It should be if managed correctly, but that is not realistic at the moment. The hot and cold feed shower would be an option if anyone was making them.

I was thinking if I can supply constant at 50/60 degrees constant to a mixer, job done, I don't think overheat would be a problem from solar and the boiler can be set to heat to a certain temp in the tank, so really it would be an appliance with coupling suitable for higher tempature than the usual cold feed with a power rating capable of hitting 50/60 degrees.

smuggler.ie

I thought they are called bath mixer taps and widely available....

As you intend to heat water, by means of solar/oil/immersion in the tank, why another electrical heating unit on top of it ? You might need to rise the pressure, but this done by shower pump.

Back to your idea... and i dont know if this would be OK by plumbing rules, regulations, etc. you could potentially feed el shower with hot water from the tank, but introduce temperature regulating valve thermostatic mixing valve in the line, just to keep temperature allowed to el shower, however, you need to ensure it does not create "water starvation" at the el shower.

Still not sure if this isn't crazy setup

DFB-D

https://www.boards.ie/discussion/comment/119892091#Comment_119892091

I actually have a thermostatic mixer and pressure pump already installed.

Issue is when water is a lower temperature than required, and I want to boost heat on demand rather than running immersion many times a day with a lot of wastage, if that makes sense? The pressure pump is brilliant, but obviously much more water is required.

Using a mains electric shower may be the only option but straight away, no warrenty and probably not a good idea to leave the pressure pump on the cheap looking fittings/pump, and the max supply temperature is the showering temperature which means tank does not last long 🙄

Sleeper12

Here's the thing. An electric shower is costs over €1000 supplied & fitted. The average life span of an electric shower is 10 years. A replacement electric shower is around €400 supplied & fitted. Out laying so much money just to top up warm water is pretty much "out there". You could never save this outlay over the lifespan of the shower.

It is far cheaper to top up the warm water with the electric immersion. The immersion is A energy rated, the same as the electric shower.

What would be far better value would be to install a timer or boost button for the immersion when needed. I have a boost button that can turn on the immersion for 30, 60 or 120 minutes at a time.

As far as electric showers are concerned they must be connected to the cold water supply only. Electric showers have to pass certain safety standards such as BEAB. They are only certified as safe when connected to the cold water supply

Connecting they to warm water can be very dangerous

OP I don't think you realise how little difference there is in price of topping up the warm water with immersion and electric shower.

smuggler.ie

@Sleeper12 Out of curiosity, what are the dangers there ? Genuine question.

Supply temp will vary during seasons , i guess from 5 to 20 C. Is there technological limitation to el shower itself, per say, temp above 40 might melt fittings. Other?

I guess that there might be scalding risk should, if fitted, thermostatic mixing valve fail.

Sleeper12

Very real risk of scalding.

Electric shower hasn't passed safely test's when connected to the hot water supply. Connecting to the hot water supply voids everything to do with the shower from warranty to possibly insurance payout in the case of a disaster. The Showers BEAB, CE etc certs become redundant.

DFB-D

https://www.boards.ie/discussion/comment/119893183#Comment_119893183

It is the cold cost I am worried about and given the tank size (limited space for an upgrade), 1 shower with the pressure boost drains the tank.

I can fit myself and I already have a priority unit and need to spend money anyway, so the outlay is probably not concerning.

Obviously the risk of scalding is a concern, is that from the electrical element malfunctioning or from the supply water?

Sleeper12

Only a REC is permitted to install an electric shower.

You plan makes absolutely no financial sense. If you want an electric shower with a cold feed then I understand that. Instant hot water & all of that. Installing an electric shower just to top up the warm water makes no sense. A complete waste of money compared to modifying your existing setup. Make your existing setup more efficient and save more money than installing an electric shower.

There are far cheaper options that will give better results. Simplist thing is to reduce the flow of your existing shower. This way you will get more showers from a tank of water. Reducing the flow by 50% gives a double the amount of showers you get from a tank of water. As mentioned earlier installing a 30 minute boost button will top up a warm tank of water.

DFB-D

https://www.boards.ie/discussion/comment/119893985#Comment_119893985

The electrical work would come under replacement, so I think that is OK and eitherway if not, I can get it overseen by a friend for no cost. The fall back is to reconnect a simple electric shower with no solar and no pressure pump.

Look you make good points, but the flow rate is kinda nice, etc. But yes, I can see that would save money.

I think with solar, what I am proposing would make sense in the future, the main reason immersions have survived is that only 1 electric shower can be running at 1 time. Other than that they are wasteful in a modern application. So how will electric showers adapt to solar water in the future?

For example -

https://www.boards.ie/discussion/2055676990/solar-panels-and-showers

Sleeper12

Only a REC can replace an electric shower. Your friend can't cert your work.

I can't imagine anyone here giving you advice on how to install an electric shower for using warm water. As pointed out in the first reply (I think) we have stored hot water or instant hot water. You aren't the first to suggest connecting an electric shower to warm water. There is a very good reason why Triton, Mira etc don't make such an item. There isn't a hybrid for safety reasons.

I'd suggest keeping the setup you have & also install an electric shower.

DFB-D

https://www.boards.ie/discussion/comment/119894185#Comment_119894185

Like for like is permitted as far as I was aware, but look I'll take advice from him either way. He wouldn't charge to connect the unit anyway.

Point was to ask for a unit designed to work! I don't think it is technologically impossible, a motorised valve, temp sensor and controller can control scald risk, but maybe triton etc don't like dealing with uncertainty in the supply temp and the extra cost to deal with potentially variable pressures. It used to be a thing on washing machines where there was a hot and cold feed, but I'd say the parts were much more durable back then.

Looks like solar wouldn't deliver any cost savings really for me. I'll leave the plumbing in place behind the wall for the hot feed and probably use the cold for mains for gravity tank depending on the shower.

meercat

https://www.boards.ie/discussion/comment/119894322#Comment_119894322

Sleeper12 is correct when he says only a rec is permitted to do this. Like for like replacement doesn’t apply to special locations which bathrooms are. When the shower is installed it has to be tested and certified to ensure proper operation.

most older shower installations are wired with 6mm cable. The new shower should be 10mm.

some older showers don’t have rcd protection and it’s a regulation.

also some older houses haven’t got sufficient main cable sizing and earthing that would take the additional load of modern instant showers

this is why a like for like replacement is not permitted