PV immersion heater proportional control

[MicraShed]

I now have an ImmerSun and despite rain of Biblical proportions it is dumping (some) electricity into the hot water tank (well the immersion heater obviously - not just dumping raw power into the tank!).

Roll on the sunshine!

 

[Scobo]

Must say, the Immersun looks a good quality piece of kit going by that photo.
Might consider upgrading from my cheapo controller if the price comes down a bit.

 

[series530]

Hi Worcester,

that's a very useful site and one I stumbled upon by accident about two months ago. It's no co-incidence, therefore, that my design is based upon designs and hardware from that site. What I have done is to take a solution offered by one of those members and have added additional functionality to it.

The past month or so has been full of week long business trips and I haven't been in a position to finalise my solution and publish it. Rest assured that, with a bit of luck, I will publish something on that site and link to it on here in the coming week or so. The whole point of the site is that it is open source and thus available for anybody to freely use provided written recognition is given to the original designer if code is used.

For those who are interested, and as a simple introduction, if you are reasonably handy with a soldering iron and can follow simple instructions to program a micro controller, it's quite easy to build a controller. Pretty well all of the parts are available at reasonable prices through the open energy monitor site and the software is simply down loadable (the beauty being that the contributors offer what they have written as open source).

For most of us, and I know that this cuts across best practise in the electrical industry, the only rub is intercepting the mains feed to the immersion heater. What many build as a solution may not be seen as industrial enough for a qualified electrician to put his name against installing. It doesn't mean that what is offered for installation is unsafe, far from it. It's just that the mains interface may not always be something that an electrician would naturally buy from a wholesaler. More industrial solutions for the mains interface can be purchased but this does increase the end price somewhat.

 

[MicraShed]

PV Update - last week with its Biblical rain storms saw a reduced PV generation of just 41kWh for the week and an increased household use to 9kWh/day. Still as the days shorten I have to expect this.

Today the ImmerSun managed to dump 0.85kWh in total (though at one point it was pushing 1.2kW into the tank for a short time, the 0.85 is the total) into the immersion heater which saw water at the tap reaching a flesh melting 67 degrees.
Now given I have smallish children I dont want it set this high.
Thanks to W2G's advice I isolated the immersion from the mains whan I got in from work and whipped the cap off - its been 17 years at least since I saw this last, in fact Im fairly sure dad wired it up not me.

Set originally at the 70 degree(ish) mark I felt it click at the 65 degree mark (so the taps are at 67 degrees at the moment).
I have turned it down to about 60 degrees, hoping that it might be about 57 degrees ish at the taps but I suspect there will be further mucking about to do to fine tune it.

After a bath was run, the tank filled up with cold to replace the hot drawn and settled at 61 degrees with a couple of gallons of cold (at 16 degrees) filling it

 

[jason121]

install a TMV on the tank that way you increase the tank temperature with the immersun

 

[MicraShed]

Well yes that is an option, but in the meantime I want to aim to keep the tank temp between 55 and 57 degrees if possible until such time as I can get around to further plumbing shenanigans!
So for now fiddling with the immersion element thermostat is my option. Ultimately I want to replace this element with a modern one with thermal cut out, but again plumbing shenanigans and draining the system down - so I'll probably leave that til next summer.

The boiler feed is regulated to 55/56 degrees via a tank thermostat.

 

[Barry ugen]

there is a unit on the market called a immersun, i have not installed yet is there anyone out there who has??

 

[Worcester]

Barry, there are loads of them installed (we know, we've done a lot of them ) if you read this thread from the beggining, I know it's 127 posts long, you'll see end users actual thought processes for deciding to install it and the results they are getting.

Generally not just good reviews - GREAT reviews!

 

[MicraShed]

Barry
Admittedly my tank is already warm, and quite well insulated but despite only pushing half a kilowatt hour into the tank yesterday and 0.8kWh today it has raised the temp from 55 degrees to nearly 70 degrees with electricity that would otherwise been exported.

Raising the temp of the tank also prevents the boiler stat from triggering and making the boiler fire up to heat the water, thus saving me gas too. As the heating still isnt on yet I can ensure that the spare electric is being used rather than exported!

 

[adamcharvet]

I've just spoken to both Jo and Lee at Immersun and their product seems to be the one to go for. And in cases where the immersion isn't on its own circuit, all you have to do is run a small twinned pair cable (similar to cat 5, I guess) from the CT up to where the Immersun box is installed. They are talking about having a wireless signal from the CT available shortly too for these cases. I must admit I have no experience with the Woolridge Device, but unless they've come down in price or can demonstrate why their product is better, I'd go with Immersun, as they seem to have got the product support and documentation right.

- - - Updated - - -

I've just spoken to both Jo and Lee at Immersun and their product seems to be the one to go for. And in cases where the immersion isn't on its own circuit, all you have to do is run a small twinned pair cable (similar to cat 5, I guess) from the CT up to where the Immersun box is installed. They are talking about having a wireless signal from the CT available shortly too for these cases. I must admit I have no experience with the Woolridge Device, but unless they've come down in price or can demonstrate why their product is better, I'd go with Immersun, as they seem to have got the product support and documentation right.

 

[Graeme Harrold]

Just ordered 2 Immersun units from Edmonsons (same price as buying direct) and also spoken with Jo. They know their stuff and their customer service seems to be impeccable.

 

[echase]

Problem with Immersun is it is a burst fire device and is not approved for installation because in most installations it causes an illegal amount of lighting flicker on all houses in the area. Also the electricity supply companies do not like burst fire technology so may later make it very difficult for owners of such devices e.g. when they fit smart meters. Try Intelligent Immersion Ltd instead for a legal product. www.intelligent-immersion.co.uk

 

[JulianC]

Proof please

 

[thushar]

Immersun looks very expensive - @ £400 .

Found a new proportional / modulation control unit at an affordable price of £199 + £9 for postage at SolarImmersion ? Surplus Solar Energy Water Heater | . It will divert 100% of the surplus power to the immersion and no need to change the immersion heater or the tank.

The feature list looks very good as well

 

[series530]

Immersun looks very expensive - @ £400 .

Found a new proportional / modulation control unit at an affordable price of £199 + £9 for postage at SolarImmersion ? Surplus Solar Energy Water Heater | . It will divert 100% of the surplus power to the immersion and no need to change the immersion heater or the tank.

The feature list looks very good as well

for the money, that looks like a pretty good system. It's a little like my home grown system but without all of the effort that I had to put in building and programming it.

if nothing else it demonstrates that the cost of these units is coming down as competition increases.