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Author Topic: Stratification problem with Solar iBoost  (Read 408 times)
RussJ
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« on: May 08, 2018, 05:43:09 PM »

I decided it was better to start a new thread after all....
The old thread is just below this one if you need to look at the installation.

I'm resurrecting an old post of mine as I need some more advice please and there are pictures here of my handywork!
My system has been working fine but I am  finding that on a sunny day the hot water is very hot but there ain't much of it...
The iBoost switches off well before the tank is fully heated so lots of my generation is "wasted".
Reading up it seems that stratification is occurring so that the top of the tank is 75C or a bit more and the bottom is cool.
I need to install a small 12v  pump to circulate the water so I get a full tank of hot water.
I thought of putting the pump in the lower copper pipe and forcing water through the Willis heater and controlling the pump via a standard tankstat fitted at the top of the tank.
As the water gets too hot it will switch on the pump and then the temperature should fall switching the pump off. As it heats up again the pump will be triggered and the cycle repeats.
I'm no heating engineer (as you probably can guess) but would this work?
Any better solutions please?
Russ
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TheFairway
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« Reply #1 on: May 08, 2018, 09:20:27 PM »

Can you fit a longer immersion? Not perfect but...
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knighty
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« Reply #2 on: May 09, 2018, 09:43:00 AM »

the immersion is external to the tank (in a solar siphon thingie)

why a 12v pump?

you can get hot water circulation pumps, (mate for freshwater) that are 240v - all the big central heating companies make them


I'd fit it at the bottom, to the feed into the solar siphon

as you said, power it through a thermostat at the top of the tank

you could always add another thermostat to the solar siphon, so if either the top of the tank or the heater get up to temp the pump kicks in? - from the other thread you were struggling to get enough flow to get the most out of the heater?

thermostats are cheap so it's no big deal to fix an extra one... about a fiver on ebay and you'll have a nice digital read out of the temp too :-)


EDIT: they've gone up a bit in price since I last bought some
£12 delivered https://www.ebay.co.uk/itm/272449421127 (uk so faster delivery)
£7.30 delivered https://www.ebay.co.uk/itm/321876819736 (from china so a couple of weeks for delivery)
« Last Edit: May 09, 2018, 09:47:16 AM by knighty » Logged
brackwell
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« Reply #3 on: May 09, 2018, 10:14:09 AM »

I thought to do this back along but did not like the the complete overkill of a CH pump as it would only be on for seconds. When I tried to find a small pump, like a fish tank pump, i drew a blank because of the potential water temp.

Do you know what length the immersion heater element that you are using.?  You can always get longer.  In the end i concluded it was probably not worth while.  Capturing more heat for what purpose? just because you can?  In the shoulder months it may allow you to go from 1 days hot water to 2 days.  I think the problem only really exists in Summer. More hot water in a bigger tank also has more heat losses

Anyways best use of PV leccy is to charge a EV !

Ken
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Tinbum
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« Reply #4 on: May 09, 2018, 12:45:05 PM »

I thought to do this back along but did not like the the complete overkill of a CH pump as it would only be on for seconds. When I tried to find a small pump, like a fish tank pump, i drew a blank because of the potential water temp.
Ken

Webasto or Eberspächer pump would be ideal.

I have seen them cheaper but something like this;

https://www.ebay.co.uk/itm/600L-H-Water-Circulation-Pump-Stable-Thermo-Heater-12V-For-Eberspacher-Webasto/232641518475?epid=28018301223&hash=item362a83db8b:g:57MAAOSw4DJaaGbi
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sunandwindy
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« Reply #5 on: May 15, 2018, 12:53:49 PM »

What I did was to install a second heater at the base of the tank which is controlled by a thermostat with a remote probe, so when the tank reaches 'x' temp, the stat switches from the top heater to the bottom heater. The heat from the base of the tank is then drawn off for under floor heating in the bathroom.
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Pile-o-stone
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« Reply #6 on: May 15, 2018, 01:19:00 PM »

What I did was to install a second heater at the base of the tank which is controlled by a thermostat with a remote probe, so when the tank reaches 'x' temp, the stat switches from the top heater to the bottom heater. The heat from the base of the tank is then drawn off for under floor heating in the bathroom.

The latest version of the iBoost has something similar built in. Once the top immersion thermostat reaches temperature, it switches to a second immersion heater lower down.
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linesrg
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« Reply #7 on: May 15, 2018, 03:17:14 PM »

Good Afternoon All,

The Immersun can do the same thing with two immersion heaters - my system uses this.

Regards

Richard
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