Solar Panel immersion heater automatic switch.

[thushar]

SolarImmersion (http://solarimmersion.co.uk) is having a special offer now - Price is only £199 (was £249) !! may be the best time to buy it http://solarimmersion.co.uk

 

[Glynn Fletcher]

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.

 

[ex 2 Base]

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

 

[echase]

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

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.

 

[Glynn Fletcher]

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.

 

[Trader9]

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.

 

[ex 2 Base]

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

 

[sharpener]

By using the Xc component its act as a loss dropper without the heat loss.

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.

 

[Dan]

Don't mind me while I bump some threads in the solar PV forum. If they're not current or applicable topics, just ignore the threads; they'll drop off the page. If they are, feel free to chip in and chat solar stuff in the solar panels forum.