Immersion Heater - PV electricity

[rondo]

Hi Paul, aquired 1kw immersion heater from source you reccomended and fitted ,works a treat on topping up between boiler firings.
Would you know if there is a remote switching device available (to switch the 1kw 230v heater) trying to save my legs up and down the stairs. I guess that would be 230v x 5amp capacity?

Many Thanks Ron.

 

[pauldreed]

Hi Paul, aquired 1kw immersion heater from source you reccomended and fitted ,works a treat on topping up between boiler firings.
Would you know if there is a remote switching device available (to switch the 1kw 230v heater) trying to save my legs up and down the stairs. I guess that would be 230v x 5amp capacity?

Many Thanks Ron.

The only commercially available 'automatic' switching unit that I am aware of is called EMMA - Solar and Wind Applications Ltd but it very expensive and probably not suitable for your needs.
However, there are a number of people who are developing switching units, and it is only a matter of time before an affordable unit is made available.

 

[pauldreed]

Hi Paul, aquired 1kw immersion heater from source you reccomended and fitted ,works a treat on topping up between boiler firings.
Would you know if there is a remote switching device available (to switch the 1kw 230v heater) trying to save my legs up and down the stairs. I guess that would be 230v x 5amp capacity?

Many Thanks Ron.

.....until a competitively priced 'automatic' switcher is developed, you could try something like this 3 Remote Control Mains Plug Sockets & Transmitter which although does not control the heater automatically, it would enable you to switch it on and off from downstairs, saving your legs!!
There are many similar ones for sale - many even cheaper, usually in big supermarkets/diy stores, and this particular one for example will switch 2900 watts, and because the remote control works by wireless (and not infrared), it will work through walls and ceilings, and up to 20 mtrs away.

...just a thought...

 

[inie meanie]

Hi again Paul.

Well I have just run some tests using an accurate industrial power meter that shows direction of power flow and power factor as it is referenced to the voltage. I balanced my 3 kw kettle using my circuit running it at various loads depending on power that was available. My consumption meter is divided in 100ths of a kwhr and each digit takes 8 flashes from an led before it moves. I ran the export rate right down to 10 watts with some fluctuations but I kept it pretty level. At no time did the import meter show any input. I have discussed the principal with another electrical engineer who also believes that the power meter will average the consumption over the duration of the cycle. If this was not the case the rather expensive Emma unit would not work either. I am really happy with my tests and will now continue with the rest of the measurement side development. I do understand your principal of why it should bring power in during the cycle, but in real life tests it doesn't seem to work like that.

 

[pauldreed]

Hi again Paul.

Well I have just run some tests using an accurate industrial power meter that shows direction of power flow and power factor as it is referenced to the voltage. I balanced my 3 kw kettle using my circuit running it at various loads depending on power that was available. My consumption meter is divided in 100ths of a kwhr and each digit takes 8 flashes from an led before it moves. I ran the export rate right down to 10 watts with some fluctuations but I kept it pretty level. At no time did the import meter show any input. I have discussed the principal with another electrical engineer who also believes that the power meter will average the consumption over the duration of the cycle. If this was not the case the rather expensive Emma unit would not work either. I am really happy with my tests and will now continue with the rest of the measurement side development. I do understand your principal of why it should bring power in during the cycle, but in real life tests it doesn't seem to work like that.

If this is the case, then it opens up opportunities to automatically vary the power supplied to the element from zero up to the full 3kw on sunny days, and of course use 'off the shelf' cheap 3kw elements too.
I was basing my opinion of 'theory' rather than 'practice', but pleased it is working out.

 

[inie meanie]

Yes it does seem that way. I am going to do further tests at a friends house who has a different type of energy meter. And I do like to make sure of these things so I will be repeating my tests under different day light conditions. I have two tanks both with 3 kw heaters fitted this is what is driving me on as it's all there just waiting to be used. The key will now be to use the correct type of measurement coils and accurately plot the slope. This could either be used on a multi output programmable relay ( changing resistances at steps ) or with more work a method of connecting the op amp output to drive the 555 timer circuit that fires the Triac. Any body had any experience of that type of interface? Or which is the best current coils to try?

 

[inie meanie]

Hi Mac
Just to put your mind at rest, your idea will work. The usage meter measures rms and gives the average across the cycle and not sub cycle. This means that a spike causing a draw from the grid will not be seen by the meter. I have completed a series of tests that confirmed this, so develop away. I am currently working on my system. When completed I will be happy to pass the details on. Good luck with yours.

 

[pauldreed]

Hi Mac
Just to put your mind at rest, your idea will work. The usage meter measures rms and gives the average across the cycle and not sub cycle. This means that a spike causing a draw from the grid will not be seen by the meter. I have completed a series of tests that confirmed this, so develop away. I am currently working on my system. When completed I will be happy to pass the details on. Good luck with yours.

Mac,
inie meanie and myself have been discussing this outside outside of the forum, and I also now agree with inie's version, that the meter will average out the power usage.
So this does look the way forward after all.....

 

[mikeh0512]

Maybe this dimmer will solve your problems

Cebek 2000W Light Dimmer

Mike

 

[inie meanie]

Hi Mike
That would be fantastic apart from the fact that you would have to sit there adjusting the pot. I have just bought a triac control unit that will take 0 to 10 volts to control upto 25 amps. If I can provide that voltage from a comparitor circuit measuring the coils. Bingo! Hope to complete soon.

 

[Millerman]

Paul.

"Can you expand on this?
Are you using a 1kw or 3kw element, and if 3kw - how are you limiting it's power dump? "

I am using a my original 3kw element. the unit i have purchsed is a Crouzet controller M3, and a thyristor controller.
The M3 controller measures the current from the grid and solar using CT's, then compares the two.
This then sends a 0 - 10 V DC signal that operates the thyrister controller ( 0 v Dc = 0 watts, 10 v Dc = 3000 watts.

The only down side is the way the solar supply is connected to the house fuseboard (by the contractor). It might have to be changed for this system to work.

 

[pauldreed]

I have fitted a 26" 1kw element, so the power dump is either zero or 1kw.Most of the renta roof installers don't like to wire directly into the fuseboard, as they like their systems to run completely independently (so anything I do won't affect their system), so I was lucky. I did however have to wire a separate feed for the immersion heater, so it didn't use the immersion power in my unit's calculations.
You could probably simply fit a Henley Block between the meter and the fuseboard, to separate the system.

Was calibration of your system difficult?

 

[Millerman]

Paul,

You have hit the nail on the head. One installer (AshadeGreener) fitted a seperate fuseboard and then linked it to the grid via new meter tails and a henley block(mother's house). When i had my solar panels fitted the installers (Homesun) they went directly into my existing fuseboard. (this was quickly changed) Both methods are correct according to th IEE regs.

This forum is about using the surplus available power and using it in an immersion heater. I have just elected to keep my existing immersion heater 3Kw and use a off the shelf controller to run it.
A 2.5 Kw controller is as little as £50
Plc is about £100
CT's are about £70 Pair (probably find cheaper) need them to be 4 - 20ma or 0 - 10v Dc output

Dont suppose anyone know how i can reduce this cost (CT's) ??

 

[Millerman]

Direct email address.

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Millerman

 

[Millerman]

direct email
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