Solar Panel immersion heater automatic switch.

Discuss Solar Panel immersion heater automatic switch. in the Solar PV Forum | Solar Panels Forum area at ElectriciansForums.net

madmurg said:
There is an interesting thread at the
Solar Energy Management | OpenEnergyMonitor


The "OpenEnergyMonitor" thread is a bit too technical for me, with only a basic electrical knowledge, even though it might offer a solution to dumping excess solar power into an immersion heater.

I'd guess that for most of the time, there will not be enough power from say, a 4kW PV system to feed a 3kW immersion heater as well as all the other gadgets in the house, so some have suggested replacing a 3kW element with a 1kW element. The drawback with this is that it won't be much use if you need a supply of hot water quickly.

As a simple alternative, can anyone see a problem with using a dual-element immersion heater, with the 3kW elements operated individually for rapid heating and in series when powered by the PV system? If my maths is correct, this should give an effective load of 1.5kW, which is much more likely to fall within the PV system output.

I suppose the heater could be wired to some sort of relay, using a change over switch to select the mode of operation.
Click to expand...
 
Hi RS-232

I have two 3kW heaters in my tank so I use a 3.3kVA isolation transformer with the centre tap earth removed so I have use of 55V and 110V. I then use relays to switch between the two voltages to give me five different loads 160W, 320W 660W 820W and 1.320W. This works well and I have hot water by midday. I use a single Arduino to monitor the solar and house load and do the switching. Since January I have averaged 24% (272kWh) of all generation into hot water that would have gone back to the grid as surplus.

Regards, Trader9
 
An interesting set-up Trader9, but controlling such a system electronically would be beyond my capabilities! When you say that you have two 3kW heaters, are they combined, as in a dual-element heater, or are they separate units? Also, suppose that you need to heat your water quickly - can you run one or the other heater from 240V (i.e. 3kW)?
 
Hi RS-232

They are the normal 3kW immersion and the 3kW boost both wired separately. I could wire them in series but I normally rely on off peak heating overnight and then solar all day, so off peak is reduced. Also I don't suppose that 1.5kW will be available that often in the winter. I can always use the boost to heat water if needed.

Come the summer (if ever it stops raining) I hope to switch off the off-peak and run solar only. Did actually manage it for the last week of April when it was like summer. You do need a system that cuts in at a low wattage so you can use it in the winter.

The Arduino is only £22 and you would need two efergy sensors (CT's) four resistors and a capacitor for the sensor interface. I am working on a simpler version using the Arduino directly driving a solid state relay (SSR) and this could be a simple solution, but I am still waiting for the SSR from Hong Kong but all in would be a simple cheap solution if it works. About £70.00

Hell, if I am sixty-four years old and using microprocessors, SSR, Ct's and LED's then it can't be that difficult. I will keep you posted on how my new system progresses.

Regards, Trader9.
 
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RS-232 said:
madmurg said:
There is an interesting thread at the
Solar Energy Management | OpenEnergyMonitor


The "OpenEnergyMonitor" thread is a bit too technical for me, with only a basic electrical knowledge, even though it might offer a solution to dumping excess solar power into an immersion heater.

I'd guess that for most of the time, there will not be enough power from say, a 4kW PV system to feed a 3kW immersion heater as well as all the other gadgets in the house, so some have suggested replacing a 3kW element with a 1kW element. The drawback with this is that it won't be much use if you need a supply of hot water quickly.

As a simple alternative, can anyone see a problem with using a dual-element immersion heater, with the 3kW elements operated individually for rapid heating and in series when powered by the PV system? If my maths is correct, this should give an effective load of 1.5kW, which is much more likely to fall within the PV system output.

I suppose the heater could be wired to some sort of relay, using a change over switch to select the mode of operation.
Click to expand...
I too thought it would be difficult to achieve but after a week or 2 browsing the Internet forums I managed to build my own controller and it works great. It really is very easy.
you do not need high wattage from your solar panels as my system heats a full tank of water using just 400w of spare power, a 3kw element will work fine using low wattage. There is no need to change to a 1kw element.
Click to expand...
 
madmurg said:
There is an interesting thread at the
Solar Energy Management | OpenEnergyMonitor

Solar Energy Management | OpenEnergyMonitor
It looks like someone has built a fully controllable solar controller useing zero cross and burst firing. This removes the need to use expensive crydom or phase angle controllers, which cost £70 plus. So you should be able to build yourself a unit for under £50.
Click to expand...


That sounds great.

Do you mean the power controller based solution from kemo electronic? I'm struggling to find the actual circuit or component relates to zero cross & burst firing.Could you please help with a schematic or part no or a link please ?
 
madmurg said:
Not at £250
Click to expand...

People think they can make something similar for a lot less but the reality is often that after few false starts they have a box full of discarded or blown up parts that, together with the parts that do make their way into a working product, end up costing at least £250. So it is fun designing something yourself but often no cheaper.

Or you design something really simple and cheap that does not cost effectively heat much water.
 
What do you use in the way of an EMI filter? Outfits like EMMA, not to mention the DNOs, are very concerned about EMC, and I wouldn't want to ruin my computer!
 
Here is a fully compliant system running 9 (yes 9) immersion heaters only using PV power. 3 phase system with house on one phase (so EMMA was not going to work). The power is from 27kw array and heating 3000 litre store for swimming pool and then surplus into house DHW. Not one for the purists but it was a project I had to accept.
The pool house is 70 metres from the inverters and the CT clamps measuring all three phases for PV and house loads. The system runs via RF to the sockets.
We have it running but are now fine tuning. I have got them to install 3 x 1.5kw elements in the first switches so as to get it working virtually all the time with the rest 3kw elements.
We can set the time of operation per day/ the time delay of switching from 0 minutes upwards (to allow for brief interruptions) / balance of power switching point in watts. Stepped switching so as power changes the immersions switch on or off to keep it all positive.
Key is getting the programme correct so as to minimise the export potential. As customer is getting paid for production and deemed export so a little bit of export is allowable! Import is a no, no.

IMG_0255.jpg
 
Why wait, Immmersun already does it :) fully proportional and more:, cascade, additonal boiler / timer (see legionella) Plus more yet to come ...
 
I agree also that it is quite expensive but as I since electrical knowledge is needed making on your own is really in need. If you want to save more then solar panel could really help you.
 
Gavin, I was just reading your link on your website - you mention that this could also be used to divert power to the dishwasher or washing machine. Can it really work that way? Surely as soon as the washing machine starts, you need it to complete the whole cycle? What am I missing?
 
The Immersun only works on a resitive load, anything with motors/electronic controllers will not work, may even damage them, so washing machines/dishwashers are not suitable - and generally they are plugged into the ring main.

Resistive loads include immersions and storage heaters (as long as these don't have a fan) and should be on their own dedicated circuit.
 
As well as the standard proportional output functions, it can also be daisy chained for higher output (or consuming) systems, the proprtional output can be 'rolled' over to a second resistive load if the immersion is up to temperature, it has a built in relay that can be controlled by various functions and features to control any load that you like, resistive or inductive.

How you can use and configure the controller is really down to your imagination - that relay for example can be used to trigger the normal boiler (you next least cost heating option of your choice) to come on at the end of the day to ensure that the hot water is up to temperature say during winterm, or on an overclouded rainy sunny day (like today for us:))

In our case (oil) we use the timer to to trigger the immersion on at 7:30pm for an hour, if it doesn't need it, eben though it's on. the immersion of course won't draw the power ..

Imagination is more important than knowledge (Einstein)
 
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Worcester said:
How you can use and configure the controller is really down to your imagination - that relay for example can be used to trigger the normal boiler (you next least cost heating option of your choice) to come on at the end of the day to ensure that the hot water is up to temperature say during winterm, or on an overclouded rainy sunny day (like today for us:))
Click to expand...
I can see what you're saying but wouldn't it be easier to just have your oil boiler programmed as normal, if the tank temp is low then the tank stat will call for heat from the boiler anyway.
 
Worcester
I've had a look at your link and some of your news articles, can you explain fiurther on the following:

'so once the water is hot, it will then send the excess power to a storage radiator, whilst still constantly monitoring the immersion to ensure a full tank of hot water'

How does it monitor the immersion in such a way?
 
Aha, it knows if it is drawing power on not - it also monitors when trying to send power to the proportionally controlled circuit wether any is going there, if it isn't it will then send it to the second load, and then every minute go back and check to see if the immersion needs it - so if the immersion (or primary load doesn;t need it) it could either send a proportionally controlled power to another resitive load, or switch on a de-stratification pump, then send the power back to the immersion when it is ready.


Simples as Sergei would say :)
 
yellowvanman said:
I can see what you're saying but wouldn't it be easier to just have your oil boiler programmed as normal, if the tank temp is low then the tank stat will call for heat from the boiler anyway.
Click to expand...

Yes that would work fine as well.
 
Hello Everyone, new to the forum,my first post.
I have recently had a 4kw PV array fitted to my roof and want some kind of immersion heater switch to use up the "spare" power rather than let it go back, unpaid for, to the grid. I have read about various ones that use 1 and 1.5 Kw immersion heaters but a recent one called SolarImmersion (mark 3) seems far superior. This lets you keep the 3Kw immersion heater and diverts ALL the unused power. Does anyone have one fitted or know anything about them, they are £250 which seems a lot but compared with the PV array on the roof it seems quite cheap. Thanks for reading.
Glynn.
 
Hi Glynn

Welcome to the forum. I have built my own diverter and you can to for less than £100. Last year I diverted more than 1MWh into my 3kW immersion heater. Go to the Talking Solar web site for construction details and links to the OpenEnergyMoniter site where the system came from. Only a handfull of components are required and PCB's are available.

Regards, Trader9.
 
Hello, I have recently installed a SolarImmersion mark III and very pleased with its operation. It works with my existing 3kW heater and simply uses all power that would otherwise been exported. Have not done the sums, no real data on how much hot water costs me, to figure out how long/short the payback period is but hate wasting free energy. Regards Bob
 
Hi, thanks very much trader9, I've read all about your "invention" and am very impressed. The thing is, although I am quite OK with wiring a 13 amp plug the equipment you describe may as well come out of the TARDIS. I am possibly older than your Grandad and all the valve theory I did at college seems a bit old fashioned now. The next post from Hophead really filled me with a good feeling that I should buy the SolarImmersion. If you could build one for just less than half of the cost, brilliant! If you can't build one then buying is the only option and at least this will be guaranteed for a year. Thank you both for your imputs.
Glynn.
 
Immersun installed by Worcester as part of our 4kw system on 08/03... Hot tank of water pretty much every day so far (excluding the one March day we were covered in snow!)... 37kWh in my tank instead of the grid and GCH water cycle running once a day now instead of twice and sometimes not even that depending on our hot water usage.
 
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Now the only problem I have is do I buy a SolarImmersion or a Immersun. If the two who have had them installed are both happy I am definately going to take the plunge. £250 or £350. does it really matter what's a hundred quid when the savings are so good.
Thanks to all,
Glynn.
 
Glynn Fletcher said:
Now the only problem I have is do I buy a SolarImmersion or a Immersun. If the two who have had them installed are both happy I am definately going to take the plunge. £250 or £350. does it really matter what's a hundred quid when the savings are so good.
Thanks to all,
Glynn.
Click to expand...

Just to get up to speed on this thread, before you get comfortable thinking its a decision based on just two units - there is another to consider :smiley2:

Intelligent Immersion.

again at around the 200 ish mark......
 
Thanks very much to Danesol. I've read about it and sent for details. I'm glad I found this forum. Now I can hear the inverter fan going full belt, I'm generating just over 3Kw and using hardly any. I hate paying for electricity but I hate giving it away more. Looking forward to when I can sit back in a hot bath with a can of Newcastle Brown.
Glynn.
 
Just heard back from inrelligent immersion. Very nice letter and lots of information. I think I will go for this one . They are passing on my enquiry to their wholesaller and then he will contact me with prices etc. I will of course put them on here when I get them.
Glynn
 
After reading all about the above 3 types I have gone for the one Danesol suggested, the Intelligent Immersion. This seem the best one on offer and I bought it last night for £250.00. The fitting is, I am assured, incredibly simple and then just forget about it. I'll give an update later when I receive it and it's been working for a bit. Thanks to everyone for their input.
Glynn
 
Hello Glynn, Good luck with the Intelligent Immersion and look forward to further reports. Hopefully my Solar Immersion will be just as reliable, certainly made the most of yesterdays sun. Bob
 
I have had the Intelligent immersion fitted for a few months now and can only say BRILLIANT.
Not only do you use all the power generated but the electricity supply company pay you for the half of your generated power which they assume you are sending back to the grid even though you are not sending any back.
I have the output from the Intelligent Immersion going to the immersion heater now the central heating is switched off and in the colder months when the central heating is on the output from the I/I will be switched to a storage heater which I bought off ebay for a tenner. I tried this out a few weeks ago and the storage heater was incredibly hot just when you needed it ie in the evening. Normally storage heaters are getting cooler by evening but of course mine is being heated up all day not at night.
If anyone has any doubts about getting one of these for their solar panels I say "go for it".
Glynn.
 
I have a home constructed controller for our PV system. Its basic but does work. I'm using three 400 volt, 55 micro farad capacitor with each controlled by a 24 volt dc, 25 amp relay. By selecting one in series with the immersion heater element we get approx. 400watts two 800 and three 1200 watt going to our immersion heater. Originally we had a 110 volt site transformer, I thought how much heat energy is being loss in the TX cores and windings and caps have no heat loss if they are not faulty. Three low voltage switch manually operated as and when required. I have clip on ammeter around the meter tails as an indicator. I have a question and would like to satisfy my mind, should a contactor disconnect the mains from the PV system when my/our system is connected to the immersion heater element. I'm never sure that we are taking energy from the mains. Your comments would be much appreciated. John
 
ex 2 Base said:
I have a home constructed controller for our PV system. Its basic but does work. I'm using three 400 volt, 55 micro farad capacitor with each controlled by a 24 volt dc, 25 amp relay. By selecting one in series with the immersion heater element we get approx. 400watts two 800 and three 1200 watt going to our immersion heater. Originally we had a 110 volt site transformer, I thought how much heat energy is being loss in the TX cores and windings and caps have no heat loss if they are not faulty. Three low voltage switch manually operated as and when required. I have clip on ammeter around the meter tails as an indicator. I have a question and would like to satisfy my mind, should a contactor disconnect the mains from the PV system when my/our system is connected to the immersion heater element. I'm never sure that we are taking energy from the mains. Your comments would be much appreciated. John
Click to expand...


If the mains is disconnected from the inverter it will drop out as the inverter can't deliver current without a mains connection, as otherwise it does not know how to synch with the mains frequency.

How exactly are you deciding when to switch in the next capacitor? When you measure the grid with an ammeter like this you have 2 problems:

1) It can't tell you which way the current is flowing so how do you know you are not importing current to feed your immersion?

2) Because of your large capacitors it is shifting the power factor of your house away from unity. Thus the ammeter is not reading real power consumed. In the extreme if you strapped such a capacitor across the mains with no other house load the ammeter would read lots of current but the utility meter would clock up almost no cost because the two currents are nearly 90 degrees out of phase. Your situation is somewhere in between where the current registered could be more than what the immersion is actually consuming.

You really need a measurement of real power to operate such a set up well.
 
Hi Ex 2 base,
Considering the output from the solar panels change every 12 seconds you must be sitting on top of your switch pile all day. Go for the Intelligent-Immersion .I has come down in price since I fitted mine from £250 to almost £200 and it's hands free.
 
Hi echase,

I did post here some years ago about a system I built from plans on the internet at openenergymonitor.org.

Look for Robins Mk2 solar diverter, you won't be disappointed. It cost me less than £50.00 for the parts and is now available in kit form.

Since I installed this system about three years ago I have diverted more than 4.2 MWh of surplus solar into my immersion or a night storage heater I have in the winter.

This system is simply brilliant and completely automatic once installed.

Regards Trader9.
 
Thank you trader9, not being the most competent on the computer I'll find it. Back to echase item 1, I switched off every thing connected up my watt meter to the heater element and using my clip on ammeter proved that the solar energy was going the heater. The capacitors are connected in SERIES with the element forming and RC circuit not in parallel as in power factor correction. I notice others have used a site transformer to drop the voltage , these transformers are not continuously rated and there are heat looses as well, so discounted that idea. By using the Xc component its act as a loss dropper without the heat loss. But I'd rather have a fully automatic system and will give trader9 idea a go. thank you all for your comments and interest. Ted
 
ex 2 Base said:
By using the Xc component its act as a loss dropper without the heat loss.
Click to expand...

True. I have often used the principle to power small items from 240V without using a transformer (but only where the circuit does not need to be isolated from the mains!).

But your RC circuit will still have a leading power factor, and to be any use Xc needs to be large-ish compared with R, so this effect will be quite significant and echase's comments are valid. (I recently had to fix a blown capacitor in a 125W fluorescent fitting, this was a series capacitor too and the vector diagram was quite bizarre, the value of Xc was about twice that of XL and in direct opposition to it.)

My own immersion heater controller uses an analogue multiplier to calculate the power from continuous readings of current and voltage, this gives a true power measurement - with sign - and has been working well for the last 3 years.
 
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