Input water temperature for electric shower

jouleflow · May 4, 2019

I have a solar pv system that has an Iboost fitted to send excess generation to my hot water tank. Combined with my solid fuel back boilers we almost always have hot water.

I also have a cold mains fed 11kW shower - not a power shower. I would like to feed the shower with luke warm water via a preset mixing valve probably about 20 deg C. This will increase the input temperature of the input water & should allow me to use the lower setting on the shower unit. I'm told that this is feasable & I'm sure it has been done before. I can't find any info relating to a maxmum input temperature. The mains pressure works fine I want to use some of my free hot water. Any suggestions?

Spoon · May 4, 2019

Have you tried contacting the manufacturer and asking them?

davesparks · May 4, 2019

I would have a look at the specifications for your shower, it should hopefully tell you what is required of the incoming water supply.

Gary K · May 4, 2019

I would assume that the shower is designed to be fed with mains cold water. If you feed warm water through it, you will have to increase the volume of water going through the shower so that the output temperature of the water is as required. Most showers will cut off the power to the elements if the output temp is above a preset.
My 10.5 Kw shower is only used on low power through out the year- it just outputs less water at the required temperature during the colder months when the input temp is less.

Charlie_ · May 4, 2019

Do you still have a boiler?

jouleflow · May 4, 2019

Charlie_ said:
Do you still have a boiler?

Yes we have two log burners with back boilers that both feed the tank.

jouleflow · May 4, 2019

Gary K said:
I would assume that the shower is designed to be fed with mains cold water. If you feed warm water through it, you will have to increase the volume of water going through the shower so that the output temperature of the water is as required. Most showers will cut off the power to the elements if the output temp is above a preset.
My 10.5 Kw shower is only used on low power through out the year- it just outputs less water at the required temperature during the colder months when the input temp is less.

Yes that is fine, what I believe could happen is that we will have a very fast flow on the lowest setting. Win Win.

Charlie_ · May 4, 2019

Do you use your boiler as the primary heat source or just as back up for when the other 2 are not producing heat?

Gary K · May 4, 2019

jouleflow said:
Yes that is fine, what I believe could happen is that we will have a very fast flow on the lowest setting. Win Win.

If you could pre warm the water enough, you could turn the shower to cold and still have a warm shower.
Pressure would probably be an issue so you might need a pump.

jouleflow · May 4, 2019

Charlie_ said:
Do you use your boiler as the primary heat source or just as back up for when the other 2 are not producing heat?

The log burners are our primary source of heat, they heat the water in the energy storage tank which in turn feeds the radiators & supplies mains fed hot water via a coil. This tank is always being topped up by the solar excess generation that feeds two immersion heaters. This gives us hot water throughout the year. I don't have any other boiler as I have no gas.

jouleflow · May 4, 2019

Gary K said:
If you could pre warm the water enough, you could turn the shower to cold and still have a warm shower.
Pressure would probably be an issue so you might need a pump.

The shower is mains fed so we don't have a current pressure problem. If I fit a mixing valve to control the input temperature I think the pressure would remain the same.

Charlie_ · May 4, 2019

Sorry I read that wrong, thought you said you did have a boiler..
Well that’s a good set up you have then..
Does it cope all year round with heating and hot water? How many in your house and what type of heating do you have?

jouleflow · May 4, 2019

Charlie_ said:
Sorry I read that wrong, thought you said you did have a boiler..
Well that’s a good set up you have then..
Does it cope all year round with heating and hot water? How many in your house and what type of heating do you have?

We use the log burners to heat two rooms and 8 radiators. There are also 4 economy 7 radiators to take the chill off in the morning. These keep the house nice and warm all year. The solar iboost set up takes care of the hot water. This is for a house with 4 adults.

telectrix · May 4, 2019

be civilised and use the hot water for a bath. unlike a shower, it will not swamp your jack Daniels or extinguish your smoke. if you feel the urge to have a shower, go out in the rain.

Wilko · May 4, 2019

Hi - In theory, increasing the input water temp will mean the output water can be hotter for the same flow and power, or any combination of these depending on the heater controller’s capability. However, as has been said at some point it might just trigger the unit’s thermal protection and shut it down. If you can advise the make / model we might be able to be more specific.

This one lists max input water temp as 28C, for example.

[ElectriciansForums.net] Input water temperature for electric shower

PEG · May 5, 2019

Can i ask why you are not using the mains fed HW for a mixer shower set-up?

jouleflow · May 5, 2019

Wilko said:
Hi - In theory, increasing the input water temp will mean the output water can be hotter for the same flow and power, or any combination of these depending on the heater controller’s capability. However, as has been said at some point it might just trigger the unit’s thermal protection and shut it down. If you can advise the make / model we might be able to be more specific.

This one lists max input water temp as 28C, for example.

View attachment 49166

That is a brilliant answer to my post, it confirms that it is not impossible to do, providing the input temperature is not excessive. I will now try to find similar details for my unit a Triton T80 easy fit.

jouleflow · May 5, 2019

Wilko said:
Hi - In theory, increasing the input water temp will mean the output water can be hotter for the same flow and power, or any combination of these depending on the heater controller’s capability. However, as has been said at some point it might just trigger the unit’s thermal protection and shut it down. If you can advise the make / model we might be able to be more specific.

This one lists max input water temp as 28C, for example.

View attachment 49166

That is a brilliant answer to my post, it confirms that it is not impossible to do, providing the input temperature is not excessive. I will now try to find similar details for my unit a Triton T80 easy fit.

jouleflow · May 5, 2019

PEG said:
Can i ask why you are not using the mains fed HW for a mixer shower set-up?

We don't have a gas boiler so I can't guarantee there will be sufficient hot water available 100% of the time, especially using solar.

Wilko · May 5, 2019

Hi - here’s the Triton T80 spec, if that’s your unit. It shows 28 C as the maximum input water temperature on page 4.
https://www.tlc-direct.co.uk/Technical/DataSheets/Triton/T80Z_FF_Instructions.pdf

Just to say - I’ve not seen this done before.
The mixer will be key to keeping within the shower manufacturers specs. Perhaps confirm all flows and temps with power to the heater properly switched off.

Let us know how you get on

jouleflow · May 5, 2019

Wilko said:
Hi - here’s the Triton T80 spec, if that’s your unit. It shows 28 C as the maximum input water temperature on page 4.
https://www.tlc-direct.co.uk/Technical/DataSheets/Triton/T80Z_FF_Instructions.pdf

Just to say - I’ve not seen this done before.
The mixer will be key to keeping within the shower manufacturers specs. Perhaps confirm all flows and temps with power to the heater properly switched off.

Let us know how you get on

Thanks Wilko. My plumber has a mixing valve that he uses for residential homes that is locked at 55 deg C. It is adjustable downwards & hopefully we can get it set to around 20/25 deg C. I expect this valve would not be affected by variations in flow as it is constantly adjusting to the conditions at the time. This lukewarm feed setup could also be used for other cold feed appliances such as dishwashers & washing machines. If you have excess hot water either from solar, gas or solid fuel then you could probably save money on these appliances too.

PEG · May 5, 2019

I do not know if you will gain any massive savings....the two inputs,to your mixer,will have to be the same pressure,to regulate accurately,at lower temperatures.
The element,for the higher setting,will still require the same usage,you will just get an increased flow,as it heats the warmer input,at a faster rate. You are then using more water,for the same length of shower.

You can calculate,the amount of energy required,to raise a known flow rate,at a known temperature,to the desired shower level. If the lower capacity element,can do this,then that may be worth it.

After a hard day's graft,i just want my standard flow and temperature,when in the shower,and i wouldn't be concerned about a saved penny.....in truth,i would not care,if the heat was generated,by two endangered species,being rubbed together...

sam400 · May 5, 2019

I am not a fan of electric showers I don’t find the temperature control very good and they look ugly.

Can’t you use the solar circuit to heat water indirectly in an unvented then boost the final water temp using an immersion heater?
That way you can supply a mixer shower which will have far better temperature control and possibly flow rate.

Zerax · May 6, 2019

Jouleflow... it sounds like your 'energy storage tank' is a thermal store type solution, which is fantastic ! The idea with these is that they hold a large amount of water (water has a high 'specific heat capacity' so is ideal for this) that stores heat energy from a number of sources (log burners, solar pv and tubes, off peak grid etc etc.) that is then used for whatever it needs to be used for. The tank is designed to 'stratify', i.e. very hot at the top and cooler as you go down. Therefore, heat is taken out at the appropriate height depending for the temperature required. E.g. underfloor heating uses low temperatures, so it takes heat low down, but traditional wall hung radiators need high temps, so they should take heat higher up.

A coil of pipe inside is used to input or extract heat.

Therefore... what you want is 'technically' achievable as you just want to run your shower supply from a very low level in the thermal store, with some temperature control attached to it, so as not to have water >28°C

This is really a plumbing question rather than an electrical...

jouleflow · May 6, 2019

Zerax said:
Jouleflow... it sounds like your 'energy storage tank' is a thermal store type solution, which is fantastic ! The idea with these is that they hold a large amount of water (water has a high 'specific heat capacity' so is ideal for this) that stores heat energy from a number of sources (log burners, solar pv and tubes, off peak grid etc etc.) that is then used for whatever it needs to be used for. The tank is designed to 'stratify', i.e. very hot at the top and cooler as you go down. Therefore, heat is taken out at the appropriate height depending for the temperature required. E.g. underfloor heating uses low temperatures, so it takes heat low down, but traditional wall hung radiators need high temps, so they should take heat higher up.

A coil of pipe inside is used to input or extract heat.

Therefore... what you want is 'technically' achievable as you just want to run your shower supply from a very low level in the thermal store, with some temperature control attached to it, so as not to have water >28°C

This is really a plumbing question rather than an electrical...

I agree that the post relates to plumbing but thought that solar pv users with free hot water would be more likely to have tried, researched or considered this, so I posted in the solar pv forum.

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