Immersion Heater - PV electricity

[pauldreed]

Have you established that all electricity meters can cope with this half wave rectification? For the positive half cycle you will be importing from grid and exporting for the negative half cycle, or vice versa. As long as the meter successfully averages out the power over a few cycles this is OK but if not it will register an export or import when none really exists (apart from the error between the 2 discrete steps and the real power available for export).

I have only tested it with my meter which is a Ampy 5235 and it uses exactly half the full load.
The Ampy, as with most modern meters is fitted with a flashing LED, which flashes every Watt/hour recorded by the meter, so it is easy to check.
Simply count the flashes over 6 minutes and multiply by 10 to give you kWh's.
It's not as good a solution as using a linear power controller such as the Crydom, but it's a safe option (doesn't get hot and is well isolated from the low voltage side via opto isolators), and costwise, a 6A 400V diode costs 99p from Maplins, and a double relay module at £3.99 2-Channel 5V Relay Module for Arduino PIC ARM AVR DSP | eBay

It's great that we have got some solutions to this, albeit different routes, and hope more come on board!

 

[Mark Gee]

Great to hear there are 3 viable solutions.

Am having panels installed (tomorrow!!) and I'm not an electrician (although I dabble). I have a second CU that is already being used off one circuit to power an outside office/garage/studio

Am I correct in assuming that what I need to to 'future-proof' my system (for adding an immersion later) is to get the guys to do is
1. Install another CU (I won't do that)
2. Fit a Henley/Henly block

Is that all...if so I'll get down to Screwfix for the CU this afternoon! That's after I use the scaffolding (going up now) to mess around with the chimney stack and aerial...a bodgers work is never finished ;-)

 

[suntrap]

As I said in my posting, I'm OK with using the existing CU because there is enough space inside it to clamp a current transformer on a single core of the cable where the cores are split.

 

[pauldreed]

Great to hear there are 3 viable solutions.

Am having panels installed (tomorrow!!) and I'm not an electrician (although I dabble). I have a second CU that is already being used off one circuit to power an outside office/garage/studio

Am I correct in assuming that what I need to to 'future-proof' my system (for adding an immersion later) is to get the guys to do is
1. Install another CU (I won't do that)
2. Fit a Henley/Henly block

Is that all...if so I'll get down to Screwfix for the CU this afternoon! That's after I use the scaffolding (going up now) to mess around with the chimney stack and aerial...a bodgers work is never finished ;-)

Mark, who is the installer? is it a renta roof system (like mine).

 

[echase]

1. Install another CU (I won't do that)
2. Fit a Henley/Henly block QUOTE]

No, my system requires no wiring changes. It is useful if the immersion is on its own MCB in any of the CUs, rather than having other devices hanging off that MCB. But not essential.

 

[suntrap]

Another idea which wouldn't absorb so much spare energy but would probably save proportionately more money as it displaces eletricity rather than gas (in my case) consumption: get your freezer to run while the sun's out. ISTR that the instructions for mine say that you should press the fast freeze button (which just overrides the thermostat) 24 hours before adding non-frozen food, so there is some scope for lowering the temperature below normal and letting it recover at night, hopefully not having to run the compressor at all. (They are supposed to cope with power cuts of many hours if the door isn't opened.) Of course the lower the temperature in the freezer, the faster heat gets in, so it might be a good idea to put some limit on the lower temperature or it would become wasteful. Also, you must not switch the compressor off and on in quick succession as it won't start up while the refrigerant is compressed. (It sits there stalled until a self-resetting thermal cutout disconnects it, which is wasteful and can't be good for it long term.) You would therefore need a strategy involving a timer and starting at a higher threshold of spare power than what the compressor needs.

 

[Andysimm2000]

Hi All, as I posted a few days ago, I have been working on version 2 of my solar controller, and it is now complete and fitted, so I thought that I would post a few photos..

Brilliant stuff Paul - shows what can be done - I assume that this is the "display head" and you have the "guts" else where for the CT inputs and contactor outputs.

Are you prepared to release your designs free or for a fee?

Andy

 

[pauldreed]

Brilliant stuff Paul - shows what can be done - I assume that this is the "display head" and you have the "guts" else where for the CT inputs and contactor outputs.

Are you prepared to release your designs free or for a fee?

Andy

Andy, I have tried to separate the low voltage from the high voltage side, both electrically and physically, so yes you are correct, I have 2 opto-coupled relays housed separately to switch the high voltage (£4.20 delivered from Ebay).
The 4 CT inputs however are plugged into the USB socket, directly into the board.
So in effect, I have two boxes, one as shown in the photos, and another containing the high voltage stuff.
As for the design, well I have posted full build details here including PCB layout, and the programming sketch. No fee! but lets work together, share ideas and make it better still!

 

[inie meanie]

Mine does that and also has an override to turn the immersion on if you want a top up on a sunless day. Some LEDs or an LCD are useful or else you don't know if the unit is working properly.

Looks like we have at least 3 viable solutions here. My one achieves the same aim as the others but I use cheaper components that are just as effective. The Crydom 10pcv2425 is pretty expensive (around £100) unless you find a cheap one somehow, as inie meanie did. So I went for a different approach that does not use such an expensive relay but provides the same function. My whole component cost including the box, current transformer, fuses, relay, processor board, etc. is less than just the 10pcv2425. On the other hand I am charging a modest cost for the design and for assembling it, as I don’t have the kit version available at the moment. My making them up saves you the potentially hazardous work of dealing with the mains side (but some of you are electricians so you don’t mind that).

I don't currently supply an LCD but am providing the connections for one as I do connect one to test and calibrate the units. I’ll make them available later for retrofitting when I get around to writing the full LCD software. LEDs provide much of the info that an LCD could supply.

Hi just wanted to point one thing out. My device is analogue and therefore doesn't wait for a set amount before switching a relay and therefore wasting blocks of up to 500 watts at a time. Also no mechanical relays to fail and triac package is a neat pre manufactured device with built in snubber, so high voltage side is nice and proven and only requires a pair of wires to screw down terminals. Calculation side is all low voltage stuff. 12 0 12 v. Any cost savings on the front end will soon be lost in efficiency over the long term. My system works right down to just a few watts so I can heat water at almost any level of spare capacity. This forum has been a great place to share ideas and has pushed me on to complete the system. I too considered using a switching method but I didn't like the idea of exporting 499 watts before switching on the circuit etc, it could mean the difference between a hot shower or a cool one. I am so pleased with my ability to heat water at any spare capacity form the roof I will be removing my hot water vacuum tubes and fitting more pv

 

[pauldreed]

The difficulty with buying products/kits in these circumstances is that forum members are unable to assess what they are actually buying, especially in the case of echase who will not divulge his circuitry claiming 'copyright' and protecting his own interests.
I don't know if you have adopted the same approach inie meanie, but if not, why not publish your circuitry, photos of your device, etc. so more electrically savvy members may pass opinion, and thereby reassure other members. It also stimulates advancement and results in a better product for the end-user.
A few members may copy your ideas, but many would not be able to build the units, through ability or lack of confidence, and would be reassured by the open source approach.

I don't make or sell units for anyone other than myself, but I have openly published my work, which has taken many, many hours of my time to develop, and since publication, I have had quite a lot of feedback which has made my device better still.
Solar Power Manager | OpenEnergyMonitor

 

[inie meanie]

Hi Paul
I too have spent many many hours developing and testing, and I am at the stage of deciding whether to develop into a fully commercial product. I am currently investigating patents in this area. If I am not able to proceed I will produce a drawing and try to explain the calibration process. It's all moving a bit fast at the moment, But have been told not to show the circuit. I hope you understand.

 

[pauldreed]

Hi Paul
I too have spent many many hours developing and testing, and I am at the stage of deciding whether to develop into a fully commercial product. I am currently investigating patents in this area. If I am not able to proceed I will produce a drawing and try to explain the calibration process. It's all moving a bit fast at the moment, But have been told not to show the circuit. I hope you understand.

Yes I agree, but shouldn't there be a dividing line between a commercial product and a Open Source product?
If you go down the road of producing a commercial product, then customers would have the protection set out in law and you would have the patent protection, but with a Open Source product, it is a work-in-process which the responsibility and development is jointly shared.
With both echase and yourself, you appear to be neither, and yet are promoting your individual projects without any accountability.
Are both of you insured and willing to accept the responsibility of your designs, or are you encouraging customers to accept the products as 'developmental modules' with no 'come back' to yourselves?

Sorry to be blunt, but if houses catch fire through bad design/bad component selection, which way will you jump??

If it were not for those questions, I would probably market my own device!

 

[echase]

I am shipping some units to customers next week and am hoping they will be able to give an unbiased view here of the unit’s performance. That will I hope partially make up for my reluctance to publish the design here. Full marks though to Paul for his excellent and clear posting of his design. I think the only item I share with his is the same CT.

If anyone wants a more accurate clamp style CT I recommend the Magnelab units available from Rapid Online. But >twice the price. I have 2 on a commercial system that sends my PV statistics to a web portal so the installer and I can remotely monitor my system. High accuracy is not needed for an immersion controller but is for accurate energy metering.

 

[pauldreed]

I am shipping some units to customers next week and am hoping they will be able to give an unbiased view here of the unit’s performance. That will I hope partially make up for my reluctance to publish the design here. Full marks though to Paul for his excellent and clear posting of his design. I think the only item I share with his is the same CT.

If anyone wants a more accurate clamp style CT I recommend the Magnelab units available from Rapid Online. But >twice the price. I have 2 on a commercial system that sends my PV statistics to a web portal so the installer and I can remotely monitor my system. High accuracy is not needed for an immersion controller but is for accurate energy metering.

The unit's performance is not in question!
forget the clamp meter steer..
I am questioning the safety of the unit, can you state that this unit is safe, and if not, do you have the collateral to meet any compensation claims?
Has you're product been underwritten by an insurer?
I suspect not, and if so, how do you intend to deal with any any claims?

 

[TonyL]

I don't think there would be too many people who don't recognise the concerns you raise and the answer is pretty self evident. There will be a big difference between the insured position of a person who builds and installs a device and somone selling or supplying designs for a device.

The reference to Open Source would benefit from some clarification; Open Source code, designs etc are normally supplied as a licensed product under GPL. Google GNU GPL and you will find out all about it. GPL makes it clear that the item is supplied 'as is', without any warranty of fitness for purpose or other obligation. You take the good with the defect.

The common misunderstanding with GPL is that people do not realise the obligation they ACCEPT by virtue of downloading the item to publish their amendments and enhancements. Many people do just TAKE with GPL when in fact you accept an obligation to SHARE.

When I checked with my insurers about building and contents cover when having PV installed, the reply was simple; if I was using approved products supplied and fitted by an accredited installer in compliance with building regs then there is no issue other than to ensure the value of the insurance is upped by the amount paid.

 

[pauldreed]

I hope that I haven't upset too many people by asking 'pointy' questions, but they needed to be asked, and the absence of a reply speaks volumes....

 

[echase]

If that last post was pointed at me then I previously answered you by PM so you can’t say you got no response.

As a bit of an aside I question the legal framework we have in UK. If someone has designed something they can get that design to other people in several ways:-

1. Put it in full on internet either as circuit diagram/software or as a full design with drawings/pictures.
2. Put the “low risk” (e.g. low voltage parts) on internet and only hint at the “dangerous” parts, leaving the user to work out his own design).
3. Get a DIY electronics magazine to publish it.
4. Make up finished units and sell them.
5. Make up finished units but leave all the mains side to the user to wire up.
6. Get the product fully type approved and sell it.

No. 6 is clearly the safest way, but out of no. 4-5 and 1-2 which is safer? Anyone from an idiot to the best electrician/electronic engineer can take the design from no. 1 and 2 and try to make up a unit. As the design detail, especially in no. 2, is limited the end result could be completely unsafe and injure the person using the unit. But the designer is hoping that he is not blamable, especially in no. 2. But by failing to publish a good full design he is actually encouraging dangerous experimentation.

In no. 2 can it actually be said that the low voltage side is low risk? It could drive the output in such a way as to cause a hazard, e.g. cause a relay to chatter.

No. 4 gives the public good quality units and takes away the risk that an idiot makes up the design in an unsafe way. Also feedback from early users helps to improve the product. So it improves the safety over no. 1 and no. 2.

No. 5 transfers some risk to the user but does not improve safety over no. 4 as some may make a hash of it.

I have done no. 3 before with a design that had mains relays in it and the magazine said they checked the design (and made no changes) and that there is no real liability problem with this approach. But the user can still make a very unsafe unit by comparitively minor deviations from the publised design or by sloppy constuction, so it is not a particularily safe approach.

So in summary I contest that no. 2 is the least safe approach followed by no. 1 and no. 3, even though the designer is more protected from the law that under no. 4 or 5. This is not a fair application of law when the outcome is potentially more people being injured and not the intended less.

In another part of legislation the law recognises DIY electrical efforts in that initially it was proposed to ban all solder with lead in it, but I believe that an outcry from the DIYers left it such that it is now still OK in home built products.

 

[pauldreed]

I had hoped that we all could have worked together to develop something inspirational, but it appears that personal gain has got in the way.
So to the future.. I won't be posting here further, but if you want to keep up to date with the next generation of energy management, please follow me and other devotees at openenergymonitor

Good luck Guys...

 

[bradburts]

Thats a real shame.
The best way forward isto develop a solution within an open source framework - we all havecomplimentary skills and working together is the way forwards.
Onthe practical commercial level I find it hard to see where a company would find theROI to support development, testing and qualification as there areeither patents preventing us and/or our discussions have now limitedthe field for new patents (well done all!).
We are after alltalking about a very simple design, one that would be easy to copy,easy to add new feature too and then claim as original design. Thosepursuing the commercial route would need a patent or some magic otherdevice property (cost, features, company reputation etc.) in order tohead off alternatives. The fact that several here have developedtheir own system would tend to make this case. At a certain marketsize (which seems likely) some of those playing catch up willhave surface mount and will therefore trash all for cost andreliability whilst also having a company name which can be trusted.
Certainly there's a few pounds to be made selling kits or homers. At some point I suspect that runs foul of the law though.
I recognise though thatit must be hard though for some to share the design which they havesweated blood over.
Perhaps one area wecould all share in is the status of patent protection, which may inturn help understand the best way forwards.
The Emma patentLOAD MANAGEMENT CONTROLLER - Cooper, Timothy Patrick would seem to cover all the devices which we have discussed. PerhapsI am wrong, I would be grateful for a second reading and somediscussion. If I am wrong and there was a gap in the patentthen have we now prevented new patents through our discussion?
Personally I find itquite hard to accept the Emma patent. I am sure that I have readabout similar home energy management systems in the past. I have inthe past designed control systems which monitor supply and controloutput currents to match available power (battery chargers). Where isthe intellectual effort/novelty in saying finite resource would benefit frommanaged output control or that a closed loop system needs an input function and an output function?
Sunny Boy's homemanagerSUNNY HOME MANAGER. SMA Solar Technology AG capabilities would seem to overlap the Emma patent, wonder whatthat's all about.
To open the field toboth those seeking commercial gain and, to a lesser extent, free opencollaboration then we should post any references to articles whichpre-date and therefore may invalidate the Emma patent.
In my view the Emmapatent is simply too far reaching and may stifle the development ofenergy saving devices, whilst only providing an expensive solution.That cannot be good for the planet.
If Emma were innovativeto say £200 or so (the bits cannot cost more than £50 in volume)then I would be more inclined to believe some effort which justifiedprotection and a large markup return.
Perhaps the Emma engineers worked outside the open discussion forums and have a lot of NRE to recover.........

Finally this is a discussion forum we should discuss & share.
For those struggling with construction side should look at Renewable Energy UK where Niel has a 100 and 1 microcontroller / AC control systems at low cost, usually less than £30. Last time I looked he had a solar immersion controller (no diode) using an LDR rather than CT. They are all PIC microcontroller based. Think the software is often posted so should be easy to modify. Buy a control system, buy a learn to program a PIC book (its easy to learn) and I can support your code. Buy me a system and I will write the code for you.







As we all lack patentprotection (hopefully) then what would our individual business modelsbe?Lowest product cost, most product features? – that comes fromteams and the discussions we share here.
Sell low volumes to thehome enthusiast / kit market through the forums? Hardly seems worththe effort, especially considering the safety risk. I am sure thatthose involved are properly trained and highly skilled. There ishowever a reason why standards organisations require design reviewhowever, we all make mistakes sometimes. Anyway at the end of the dayall someone in China has to do is buy a kit , reverse engineer andmass produce in surface mount. Try proving that is your design then!

 

[echase]

it appears that personal gain has got in the way.

Good luck Guys...

All my sales income apart from the component cost and postage goes to charity so it’s not for personal gain. I am thinking of switching to kits from now on.

I commend those who want to pursue the open source route but beware your own safety.