OP
pauldreed
--- It's because it's dark!
-
Please checkout the new poll we will be pushing hard, and want some good stories to come out of this
result are public - you can change your vote over time, which might genuinely be the case from time to time.
Discuss Immersion Heater - PV electricity in the Central Heating Systems area at ElectriciansForums.net
OP
pmcalli
My system balances the house load inc immersion with the solar gen. Your assumption is correct I have one CU with PV fed in via RCBO. PV plus incoming gives you all house load as PV current is flowing in opposite direction. I have since added a second cu for the solar and split the tails in a Henley block as I wanted some extra mcb outlets both ways work well. The system has been working well for the last month and my feed in has dropped to 20 percent from 60.
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inie meanie
Hi Guys
I am going to have an extra long immersion heater made. 3 KW but 48 '' long. The majority of heat will be biased at the lower end. As some of us are now getting free hot water it makes sense to try and use the whole tank. If anybody else is interested in one let me know because the more they make in one go the cheaper it will be for all of us. I have asked for a quote for one and five units to see what the difference is. It must be better than drilling into the side of the tank and risking damaging the whole thing.
I am going to have an extra long immersion heater made. 3 KW but 48 '' long. The majority of heat will be biased at the lower end. As some of us are now getting free hot water it makes sense to try and use the whole tank. If anybody else is interested in one let me know because the more they make in one go the cheaper it will be for all of us. I have asked for a quote for one and five units to see what the difference is. It must be better than drilling into the side of the tank and risking damaging the whole thing.
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pmcalli
I have just changed mine from a 27 to a 36 and only just got away with it beacuse it goes in at a slight angle. 48 would hit the boiler coil. An immersion coil where the heat is applied lower down would be of great interest.
Rather than using an extra long immersion, have you considered using a pump to simply circulate the water around the cylinder, T off from the H/W outlet at the top of the cylinder and route via a pump and a non return valve down to the C/W input at the bottom of the cylinder, switch the pump on whenever there is enough excess PV power to run the pump and immersion.
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pauldreed
Good idea....I like your lateral thinking....
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pmcalli
Excellent idea
probably a good idea to have a non return valve in the C/W input as well to prevent possiblity of pushing hot water into the cold system.
Yes but if its being fed from a header tank, make sure there is enough pressure to operate the check valve.
Taking the idea one stage further, I've actually seen a circulation pump used in a large house where there was effectively a h/w ring main around the house so the H/W was pumped around the ring and back to the bottom of the cylinder so didn't have to wait for hot water at any of the taps or showers regardless of how far they were away from the cylinder. Obviously this required copious quantities of pipe lagging but very effective.
EDIT: Looks like a spring loaded check valve might be too restrictive on a header tank C/W feed so maybe a horizontal flap type check valve might be the way to go. Haven't found any with standard 22mm compression but have found these imperial threaded ones http://www.ukpumpsupplies.co.uk/browse.asp?cat=10/106/1062/1062-2
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inie meanie
Hi well done for the abstract thought. I have just had the quote. £150 + vat for 48'' with 6'' dead zone. Hmm quite a lot really. The pump would need to be controlled carefully so that you didn't disperse useable heat if it was a low pv day.
Yes, good point, how about a cylinder stat or even a relay controlled off the immersion stat so that when the stat gets up to temp the relay turns on the pump would then circulate enough until the temp drops and the stat switches to heat again.
Oh and by the way, I definitely don't like the sound of a 6" dead zone LOL.
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pauldreed
I don't know if different 'power' pumps are available, but I would think it would only need a low flow rate to effectively circulate the water as there is only about a metre head of water and short pipe runs.
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suntrap
Many pumps have electronic speed controls and you'd probably use it at the lowest setting.
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suntrap
There's actually no head to overcome - just a minute difference in pressure caused by the difference in water density. An alternative would be to have a short piece of large diameter tube from the bottom of the element to the bottom of the tank, which would result in the water from the bottom being drawn up, but that isn't controllable.
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pauldreed
How would that work?
Wouldn't the water temp in the tube vary between the tank temp at the top, and cold at the bottom (same as the tank) and remain motionless in tandem with the tank?
From what I can see there are numerous pumps available low power, low voltage etc but they always seem to work out more expensive than a cheap central heating circulation pump. A standard CH pump removes any problems with odd sized connectors and can be simply connected using 22mm pipe and a standard 22mm check valve, set it on slowest speed and away you go. Should get the whole thing up and running for less then 50 quid.
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suntrap
If there is any temperature gradient in the water inside the top of the tube where the bottom of the element is placed, it will move and draw water up from the bottom of the tank.
I had a 1975 bungalow like that but the pipes were set into the concrete floor with probably no lagging so it had been disconnected by previous owner as not efficient. There was a standard CH type pump to pump it round.
Regarding the deadness of PV due to proposed FIT change can I encourage you to protest to relevant people as government is allegedly open for consultation. Chances are it won't kill the industry but slow it down a lot. As PV prices fall its likely that in 2-4 years the new FIT level will again return more than 5%. But they could reduce FIT further by then.
The December cut off is very unfair as many people have spent significant money on the planning process and now can’t get it installed in time to reap the full benefits, even if they have just got to the end of the porocess.
Governments of all hues have blighted the low carbon industries by stop start grant/subsidy policies.
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inie meanie
Absolutely shout as loud as possible. It will kill off many companies and stop people installing. They should have slowly reduced the tariffs not like this. It just shows that the MPs live in a bubble not the real world!
Green peace are going to launch an action in the courts on Friday
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Red Defender
The circulating pump needs to be a bronze one. Normal CH pumps are cast iron and will rust and discolour the water in the hot water cylinder.
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Red Defender
Hi all, Im new to this forum and have read everything with great interest. I was due to have a 4 Kw system fitted today but been put back to next Thursday. I have been looking for ways of optimising my consumption of my PV output and accept that using it to heat water and store it seems a good idea. The point I raise is a standard 36" x 18" cylinder will have about 25 gallons of water and from cold will take less than an hour to be heated to 65 degs. What are you going to do with the rest of your output on a clear long summers day?
My first thought was to use a low power element in the very bottom of the cylinder, say 400 watts, and using a timer, and the output profile, have the element switched on during peak hours, say 1000 to 1500 for a south facing roof. this should heat the water without importing any power from the grid and allow other surplus to be consumed by other activities.
Just a thought!
My first thought was to use a low power element in the very bottom of the cylinder, say 400 watts, and using a timer, and the output profile, have the element switched on during peak hours, say 1000 to 1500 for a south facing roof. this should heat the water without importing any power from the grid and allow other surplus to be consumed by other activities.
Just a thought!
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pauldreed
It's a quick fix, but not a very efficient one!
If you check my solar power graph for today you will see that for the majority of the day my 3.3kw system has generated less than 200W, with a short peak for a few minutes up to 800W. Now if you check the Home Power Usage graph you will see that for the majority of the time home appliances have used all of that solar power - and more besides!
A quick check of the Accumulated Heater Power graph shows that today, only 5Wh of power was switched to my immersion heater.
So my point is that if you used a simple timer, the vast majority of the immersion heater power used today would be drawn from the grid as chargeable units, especially if you were running any other appliances at the same time.
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inie meanie
Yes on a good day there is plenty of spare capacity. I use a thermostat that switches between tanks. It pulls a contactor in, then I heat the extra tank. This can be continued with another contactor to say switch over to a storage heater or under floor heating. There are many possiblities. As you have probably gathered, this forum has developed methods of only using the spare capacity and not importing. Not standing by and flicking a switch on when sunny or using a timer and hoping for the best. The systems here run automatically and switch off when not enough power is available.
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lioncrunch
Hi all just to let you all know if your meter goes back and you dont inform you supplier they can refuse to pay your FIF's
EDF condition of pv FIT's
EDF condition of pv FIT's
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lioncrunch
That should be FIT's sorry
I'll begin with the customary apology - I'm new here, so hope this fits (no -pun intended) in with the current thread.
I have solar PV and i too had been looking at EMMA, far too expensive, so I am in the process of testing a circuit which reads the flassing LED on my normal electricity meter and creates a signal to increase or reduce a controlling voltage. This is non-intrusive and low voltage using commercial PSU for the 5v. Now what I am looking for is a commercial 3kW phase controller for the immersion heater such that I need not worry about approvals, safety regs. etc should I make this for sale. Has anyone found a source of such stand-alone phase controllers (burst firing would not cust down the RMS power used per cycle). I have seen Crydom mentioned in earlier posts, any other leads wold be most welcome.
I have solar PV and i too had been looking at EMMA, far too expensive, so I am in the process of testing a circuit which reads the flassing LED on my normal electricity meter and creates a signal to increase or reduce a controlling voltage. This is non-intrusive and low voltage using commercial PSU for the 5v. Now what I am looking for is a commercial 3kW phase controller for the immersion heater such that I need not worry about approvals, safety regs. etc should I make this for sale. Has anyone found a source of such stand-alone phase controllers (burst firing would not cust down the RMS power used per cycle). I have seen Crydom mentioned in earlier posts, any other leads wold be most welcome.
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inie meanie
ERR! surley the point is you dont want to import any thing unless you need too. If you are counting red flashes you will be importing. Using a current coil, it slips around the cable and is not directly connected to it. So it is non invasive as well. You need a circuit to balance the demand to zero or just below so you export only a few watts. I have used the Crydom and it is expensive but is a nice package that can be bolted to a metal case to disperse the amount of heat it generates, which isn't too much. It will pay for it's self reasonably quickly.
Thanks for the warning, but something said earlier on in this thread (I think) put me on to a solution. The flashing rate is proportional to the import rate, so it slows down to 'off' when there is virtually no flow but then goes solid ON when exporting. I can detect this and my next stage is to use this for proportional control of the immersion heater. I understand that the clip on current meter cannot determine which way the electricity is flowing, so no use there.
As it stands at the moment, I have an indicator in the kitchen so I can manipulate my appliance loading for best use of available power - I can tumble-dry my anorac on 1Kw or 2Kw setting as appropriate
Eventually I'll have an RF link to a portable power controller for immersion heater or storage heater - if it works. I hope to be able to offer these for sale once I have proved it and created PCBs, but I do not want the responsibility for maiins safety. I recon it will cost about £50 plus power controller to do what EMMA does for £1500!
As it stands at the moment, I have an indicator in the kitchen so I can manipulate my appliance loading for best use of available power - I can tumble-dry my anorac on 1Kw or 2Kw setting as appropriate
Eventually I'll have an RF link to a portable power controller for immersion heater or storage heater - if it works. I hope to be able to offer these for sale once I have proved it and created PCBs, but I do not want the responsibility for maiins safety. I recon it will cost about £50 plus power controller to do what EMMA does for £1500!
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pauldreed
But it will be red if you are exporting 3kW and also red if you are exporting 3W, so how will you know whether there is enough residual power to run an immersion heater?
Yes, clip on current meters can determine which was the electricity is flowing, by comparing the voltage phase of the mains cycle with the current, at the same time as telling you how much current is flowing.
Good luck fella!!
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lioncrunch
Hi all, have been reading all your posts, and very interesting, but (to me) far to technical,
Whilst I have an understanding of mains electrics, electronics are magic.
Maybe one of you learned gents can tell me if this would work:
Very basic but use something like Owl, Efergy meter with alarm, in place of buzzer fix a relay connected to whatever immersion /mains socket, set alarm at desired level, and hey presto when sun shines turns on relay, free electric.
Would need something to stop relay chatter.
Thoughts please....
Whilst I have an understanding of mains electrics, electronics are magic.
Maybe one of you learned gents can tell me if this would work:
Very basic but use something like Owl, Efergy meter with alarm, in place of buzzer fix a relay connected to whatever immersion /mains socket, set alarm at desired level, and hey presto when sun shines turns on relay, free electric.
Would need something to stop relay chatter.
Thoughts please....
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Red Defender
Thanks for the replys. My first problem with any of the systems that have been developed here is distance. My mains comes into the middle of my bungalow where the main consumer unit is. The inverter is in an outbuilding som 30 meters away. The output from a clamp would be lost or degraded over that distance and therefore make comparisons more difficult. I guess the clamp output could be amplified and then re calibrated before it entered a comparitor but my days of electronic engineering where long past, OC71 transisters were replacing valves when I started.
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inie meanie
Ok simple solution . Use a current clamp that gives you a milli amp output say 4 to 20 is industry standard. Current flowing in a circuit is the same therfore distance makes no difference, if you have 6 ma at the coil you will have 6 ma at your measurement. You can get these coils from LEM.
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inie meanie
Paul. I think that sums it up very well :- )
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inie meanie
Yes in a very crude way that would work. BUT! and it is a big but! You have no way of compensating for load on the house. So you maybe importing already. Ie the washing machine may be on . the oven running? then you just switch on 3 kw of load straight off the grid.
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pauldreed
OC71?
You've just taken me back over 40 years when I started in electronic engineering!
But don't let the years hold you back - I changed career in 1979 and until the past 12 months never touched electronics. It's a steep learning curve, but the basics will hold you in good stead.
At some stage, the inverter must feed back to your consumer unit, and that's where the clamp should be fitted.
If not, you might consider using 2 of these. Which are microprocessors with RF capability, so they talk to each other, and the software provided by this site would deliver your goal.
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suntrap
Have a look at openenergymonitor.org - there is a lot there including wireless sensors. Of course if the load in the outbuilding isn't significant, you can just measure the current at the house end.
Thanks for your input.
As for your 3W v. 3kw point, my scheme will use the flash rate for feed-back. If the non-controlled house load goes up, or a cloud passes by, the led will begin to flash and the immersion heater loading will be reduced until equilibrium is restored. I've actually proved this to myself manually by selectively changing loading within the house, even down to varying load on 500W of dimmable lighting.
Interesting, I thought that the clip-on monitors only acted like a single turn transformer, I don't see how voltage phase is determined nor how it shows direction (I'm a now-redundant RF engineer working on this as a challenge, so I don't understand DC, such as mains! )
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suntrap
Current transformers are indeed unable to give you current direction, but the point is you look at the voltage as well (invasive). That's why plug-in consumption meters are theoretically more accurate than the Owl (helped by actually being able to measure the RMS voltage as well as the phase).
Unfortunately the flash rate isn't much use because you never want it to be in that mode - you always want to prevent any power coming from the grid, especially if you're trading the immersion heater off against gas which costs so much less.
I've actually come to the conclusion that although it's very satisfying to heat your water from PV, it doesn't save you that much money and it's quite an environmentally-unfriendly way of doing it if you normally use gas - the electricity should be used to offset power generation rather than domestic gas consumption. Running fridge-freezers continuously off it might (might!) be a better idea.
Unfortunately the flash rate isn't much use because you never want it to be in that mode - you always want to prevent any power coming from the grid, especially if you're trading the immersion heater off against gas which costs so much less.
I've actually come to the conclusion that although it's very satisfying to heat your water from PV, it doesn't save you that much money and it's quite an environmentally-unfriendly way of doing it if you normally use gas - the electricity should be used to offset power generation rather than domestic gas consumption. Running fridge-freezers continuously off it might (might!) be a better idea.
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In the past few months, I have monitored my weekly usage of peak, off-peak electricity and gas. For two weeks I heated water by off-peak only (i.e no solar PV to distort metering), and for another two weeks by gas only. There was very little difference in cost which surprised me.
I agree that using electricity, however generated, during peak periods (day-time) is less environmentally desireable than using off-peak. On the crude assumtion that any power I can put into the hot water tank will offset mains derived power later and that EMMA claims a theoretical return of about 8% for this alone on an expenditure of well in excess of £1500, I'm happy for me to press ahead with my home made scheme which should be almost as effective for one tenth the cost, beside its a challenge for the grey cells.
As for the flash rate, every time it records a flash, the power dumped into the immersion heater will reduce, I can live with a long period between flashes as this represents a consumption of just 1Wh.
I'll get back with my results in a moth or sos time and crow or eat humble-pie as appropriate.
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lioncrunch
Thanks Inie Meanie for reply,
I agree with your comments but I was thinking mainly during the day when at work, house uses about 400w during day set alarm for 1500w fix heater/ hot water to come on then, just a thought, but thanks anyway..
I agree with your comments but I was thinking mainly during the day when at work, house uses about 400w during day set alarm for 1500w fix heater/ hot water to come on then, just a thought, but thanks anyway..
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bumcrack
This is far to much thread to digest, and I appreciate the electronics guys will be looking for the satisfaction of designing thier own control, but for the average punter, I would look to use one of these, they are ~£100 + the cost of LEM current transducer, and mains switching devices...
CAREL
Its actually a parametric refrigeration controller, but they come with analogue and digital inputs, and 4 x volt free output contacts.
You can set them up to cascade elements on or off based on export, and add switching delays etc....they are a great bit of kit, I use them to stop biogas compressors becoming inhibited due to low ambient temperatures.
CAREL
Its actually a parametric refrigeration controller, but they come with analogue and digital inputs, and 4 x volt free output contacts.
You can set them up to cascade elements on or off based on export, and add switching delays etc....they are a great bit of kit, I use them to stop biogas compressors becoming inhibited due to low ambient temperatures.
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Maurice Sauer
Hi echase,
Having read the last 20 pages or so of this thread I am intersetd to learn more about your controller system. I have no particular wish to reinvent, nor do I have the specialist knowledge to do so, but could put together from kit or go ready built. Please provide further info on options and prices. I can't find a direct link to your e-mail address.
thanks
Mo
Having read the last 20 pages or so of this thread I am intersetd to learn more about your controller system. I have no particular wish to reinvent, nor do I have the specialist knowledge to do so, but could put together from kit or go ready built. Please provide further info on options and prices. I can't find a direct link to your e-mail address.
thanks
Mo
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Vollster
Message for EChase - yes me too - I have a customer who is particularly interested in a system to supplement a PV system we fitted recently. Could you send me some details
I like the approach Sparqui, and would be interested to know how you have been getting on since this posting.
Also would appreciate hearing from echase as to availability of his system or designs therefor (am capable of building most things from circuit diagrams).
TIA
I can't bring myself to read all 35 pages to see if anyone has mentioned one of these but they do exactly what seems to be required;
Igloo Solar Energy PV & Thermal Panels & Heat Pumps Essex London Cambridgeshire kent hertfordshire sussex surrey berkshire south east south west & midlands
Not cheap but very effective.
Igloo Solar Energy PV & Thermal Panels & Heat Pumps Essex London Cambridgeshire kent hertfordshire sussex surrey berkshire south east south west & midlands
Not cheap but very effective.
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suntrap
Yes - you could have discovered this by typing it into the search box at the top of the page. And "not cheap" is an understatement.
I sympathise, but it shows the popularity of the topic (congrats to Paul for starting it) and the excellent solutions being offered all of which are much cheaper, but many work as well.
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My Intelligent Immersion unit from echase is working fine easy to build and install, also a good price. :santa3:
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suntrap
How much, and does it have a mains filter? Oh, and can it cope with the PV being on the same consumer unit as the rest of the house, i.e no way to measure house current directly without threading several wires through the current transformer?
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You will have to speak to echase for any Technical advice on this unit.
Reply to Immersion Heater - PV electricity in the Central Heating Systems area at ElectriciansForums.net
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