topping up shower temp with instant water heater

[pt]

Has anyone used an inline electric heater to top up the temp of pre-heated water coming from a thermal store? I have a heat exchanger feeding mains pressure hot water to a mixer shower but often the water supplied is only at 20-30 degrees. It pains me to have to heat a whole tank with the immersion, just to get the top up to 60 degrees needed for a hot shower - (Yes there is a long pipe run to the shower ). The technical services dept of a supplier of instant water heaters informed me that these will not function if the incoming water is already hot.  Heating water from the cold supply seems a waste of available heat. Any suggestions?

[PEMTEK]

I would of thought a standard electric shower with a mixer on the input to limit the maximum input temperature would work well with the shower heat setting on low or off if the incoming water is too cold.

Phil

[rust]

Iv been looking @ this too.
You need to search Instantaneous & Tankless as well as inline.
Alot seem to have a set temperature increase rather than bringing any temp water upto a preset temperature.
Zip has one that will exespt pre heated water upto 50 degrees   http://www.zipheaters.co.uk/categories.asp?cat=18&subcat=28. there are lots of others to.

I do have a question though afer reading the PDF. An electric shower alters temperature by restriction flow rate, but it sounds as if this instantaneous unit varies its electrical input which sounds great... but I may well be dim... It sounds to good to be true!

Can somebody enlighten me?

[peewee]

You could try changing the plastic waste pipe from your shower with copper waste. Change the hot supply to the shower to soft copper. wrap and solder it to the waste pipe, and once it gets hot it should boost the temp.
Also you could put the 1 1/2" waste once you have wrapped it, inside a 110mm soil pipe and add some insulation.
Should do the trick if you get at least some temperature rise it will bring it up. Peewee

[pt]

Thanks for your contributions folks.
I've decided to bite the bullet and have ordered the Zip IXL9 in-line.
(http://www.tlc-direct.co.uk/Products/SOILX009.html?source=adwords&kw=ilx009&gclid=CKe1pOaaxZYCFRSO1QodSExeyQ)
It's electronically controlled and takes input water up to 50 degrees and the manufacturers say it's suitable for a solar set-up, so it's nice to know they are considering renewables at the design stage.
Rust - I don't know if the following quote from th handbook answers your question?
"The power is automatically adjusted by the electronics in line
with the water flow rate, in order to obtain the set temperature
and keep it virtually constant. The required temperature can
be set to within 1°C between 35°C and 55°C using the two
buttons and can be read off the digital display. If the full
power of the unit is insufficient to heat the water to the
required temperature, this is shown by the flashing ‘Power’
indicator. At high incoming water temperatures, the power is
automatically switched off to avoid producing excessively hot water. This is
shown by the ‘Overheat’ indicator."
I'll let you know how it goes.

[solar_cambridge]

That unit looks very interesting for situations where an immersion can't be installed. The price is not bad to pay for the  backup option so let us know how it goes. Pics would be good.

[dhaslam]

It is surprising how much energy it takes to heat the water instantly but it does seem the best solution in your situation.    I have gone a different route but then the problem is slightly.  In my case  the DHW cylinder has solar input but the separate buffer cylinder has heat pump and stove input. If the buffer tank is heated by heat pump only the water wouldn't be hot enough for showers on winter mornings.    I have ordered a difference controller from China  which will top up the temperature from the store but it also has a clock built in so it can raise  the temperature more using the immersion as necessary in the morning. 

[rust]

Rust - I don't know if the following quote from th handbook answers your question?
"The power is automatically adjusted by the electronics in line
with the water flow rate, in order to obtain the set temperature
and keep it virtually constant.

Yup - I think it does!

[pt]

OK . Just got an electrician in to finish connecting up and it works exactly as desired. Good flow rate and only adds heat as required to raise water temp to variable, pre-set value. Ignore the message on the unit that max input temp is 15 degrees, the paperwork specifies 50 degrees max for input. Also, the fitting instructions mention, in passing, a bag containing spare washers and screws. Ignore this bag at your peril  - it actually contains the plastic adaptors needed to connect the unit to 15mm pipes. If you don't use this you end up with a lash up of 4 brass fittings joined together. (Guess who didn't look in the bag early enough!). The electrician was well impressed with the unit and took all the details.

[rust]

Thank you for the update.

[KLD]

Sorry, I missed this discussion earlier.
We've got the ILX 9 installed in the kitchen (used to be too far away from the cylinder, hopefully all changed by next week).
As dhaslam noted, it takes a surprising amount of energy to heat water. The 9kW output power is OK if you have pre-heated water. With 30°C input you can get 42°C at 10 l/min. In our case, the incoming mains water in winter is about 5°C. Raising this to 42°C (could be hotter for washing up) lowers the maximum flow to just above 3 l/min. Duh.

The power is delivered by a two heaters, one is ON constantly, whereas the other is pulsed. 8.8kW at 240V are 37A: when the unit switches on, the lights in the house dim a little. In the pulsed mode the lights flicker at maybe 10Hz. --- Before I knew about this pulsing the flickering made me quite nervous (contact problems? earth problems? where did I put that fire extinguisher? )

Klaus

[Paulh_Boats]

Sorry to rain on the parade, but all this energy hungry hardware seems unnecessary.

Today our 30 tube solar panel heated a modest 120L tank to 39C at the top, which is just warm enough for our gravity shower. QED.

-Paul