OP
pauldreed
--- It's because it's dark!PV is dead. RIP PV :- (
Discuss Immersion Heater - PV electricity in the Central Heating Systems area at ElectriciansForums.net
--- It's because it's dark!PV is dead. RIP PV :- (
Hi, Ive been dircted to this thread from a discussion on the PV forum and have spent hours sifting through all the pages and some very interesting idea. I'm a little confused about your CT's and wondered if could you elaborate a bit on how everything is connected in your system. Do you simply have one CU with PV fed in via RCBO and immersion fed from MCB or is the immersion feed separated off from the CU. I've been trying to work out what the result is from your CT set up with up one on PV+Incoming and another on the PV?
I've currently got everything connected into the CU so have thought of putting a CT around all the house circuits (excluding immersion) and another on the PV thereby enabling me to calculate the excess power or maybe adding a Henley block to my set up to keep everything separate but is your method a cunning way to get round all that?
Its probably all very simple but its late and my brains dead
Cheers
John
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 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.
Good idea....I like your lateral thinking....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.
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.
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.
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.
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.
How would that work?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.
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.
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.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?
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.
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.
It's a quick fix, but not a very efficient one!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!
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!
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.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.
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?...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...
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.I understand that the clip on current meter cannot determine which way the electricity is flowing, so no use there.
Good luck fella!!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!
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.
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!!
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....
OC71?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.
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!!
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.
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.
I can't bring myself to read all 35 pages
Not cheap but very effective.
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