Immersion Heater - PV electricity

[suntrap]

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?

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.

 

[echase]

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.

 

[inie meanie]

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.

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

 

[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.

 

[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!

 

[pauldreed]

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!

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.

 

[inie meanie]

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!

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.

 

[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

 

[lioncrunch]

That should be FIT's sorry

 

[Sparqui]

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.

 

[inie meanie]

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.

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.

 

[Sparqui]

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!

 

[pauldreed]

...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...

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?

I understand that the clip on current meter cannot determine which way the electricity is flowing, so no use there.

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 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!

Good luck fella!!

 

[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....

 

[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.