PV immersion heater proportional control

[brian wright22]

Thanks Yorkshiremike. Retro fit its quite clear 20% vat then.

 

[Gavin A]

Thanks Yorkshiremike. Retro fit its quite clear 20% vat then.

top line - hot water controls.

it's 20% for the equipment only, 5% if professionally installed.

 

[sly_dog_jonah]

My understanding is the same as Gavin A's, 5% if it's installed professionally as it qualifies as a hot water controller.

pwboston, thanks for the your comment about amount of E7 you use. A couple of questions if you don't mind: How big is your tank? What temperature do you heat it to?

 

[yorkshiremike]

Thanks Gavin, I hadn't considered the heating controls paragraph, I guess the Immersun is an 'electronic timer'. On the HMRC site paragraph 2.6 is:

[h=2]2.6 Controls for central heating and hot water systems [/h]Central heating and hot water system controls include manual or electronic timers, thermostats, mechanical or electronic valves, including thermostatic radiator valves.

 

[sly_dog_jonah]

Thanks Gavin, I hadn't considered the heating controls paragraph, I guess the Immersun is an 'electronic timer'. On the HMRC site paragraph 2.6 is:

2.6 Controls for central heating and hot water systems

Central heating and hot water system controls include manual or electronic timers, thermostats, mechanical or electronic valves, including thermostatic radiator valves.

The Immersun is much more than an electronic timer, although that is one of its many functions. It's primary use-case is as a dynamic load controller, optimising diversion of exported power to a local load (usually an immersion) to maximise benefit from microgeneration while remaining grid-independent. Given the finite capacity of any heat storage, the device can't eliminate export, but it can certainly reduce a household's carbon footprint by reducing gas consumption (or electric heating).

On that basis it should certainly qualify for the 5% VAT.

 

[MicraShed]

Finally got my act together (and finished my IV antibiotics!) and ordered my ImmerSun install.

Bit of a shame its going to be the back end of the month before Im free to sort out the install, so Im heading into the wrong bit of the year - but Im still sure I'll see some benefit even now - and of course there is next summer to look forward to!

 

[pwboston]

My understanding is the same as Gavin A's, 5% if it's installed professionally as it qualifies as a hot water controller.

pwboston, thanks for the your comment about amount of E7 you use. A couple of questions if you don't mind: How big is your tank? What temperature do you heat it to?

It is a 140l tank, but the temperature is 2/3rds of the dial (no temperature reading on stat) however its hot enough not to have your hand under it.

 

[brian wright22]

sly_dog_jonah
QUOTE

Re: PV immersion heater proportional control
Brian, Would be interesting to compare those figures with your Gas savings over the same period (or similar period depending on when your meters were read by you/EDF).

Yesterday sent EDF my meter readings. Today the costs came back with a full 32 days worth of using the IMMERSUN . The Gas saving is for the 32 days so far £20.35..
This late September burst of Solar power is great for the bank balance

http://www.immersun.co.uk/downloads/...ide%20v1.0.pdf Section 5.4​

Read more: http://www.electriciansforums.net/newreply.php?do=newreply&p=598333#ixzz25nh1t6mB​

 

[nowty]

I got my Immersun today, there is not much to them so I am sure these are going to come down in price significantly over time. I am putting in a preheat tank for my water but probably won’t get round to it for a while yet. However I temporarily installed it from a wall socket, connected the sensor clamp and connected a £20 2kw electric heater (non fan type) to it.

The set up is easy peasy, whole job including the set up took about 10 mins. When I installed it after work I only had about 1 hr of sunlight left and I was generating about 1kw with the house using about 300w. It dumped about 600w into the heater and I monitored the house usage and PV generation on a combined energy meter I have got.

I have to say my first impressions are very very impressed. It settled down quite quickly and my energy meter was reading practically zero import / export. I played about with the heater controls as the one I bought has two heating elements 1250w and 720w which you can independently switch on or off. I was quite amazed that it deals within seconds with varying heater loads and adjusts its output to dump the same available power to different heater ratings.

Next I turned on the kettle and the heater stopped instantly with the Immersun display saying “waiting”. Turned the kettle off and the power returned to the heater again within seconds. Need to wait tomorrow to see how it copes with 3kw+ excess generation.

 

[regen]

Hi There,

I have been looking at both the imersun and the sola controller but which would be best for my application?

I have a 4kw pv limited to 3.6 via inverter which reguarly runs for several hours at 3.6 when sun shines and hoping to install a 1 to 2 kw hydro system on a stream with variable flow rates giving a max input of 5.6kw. This will be all fed via 2 immersion heaters into a 300 litre thermal store. Although 5.6 is max it is unlikely to be achieved with 4.5kw being the expected max for most of the time.

Regen

 

[sly_dog_jonah]

ImmerSUN have updated their FAQ recently: Frequently Asked Questions :: immerSUN :: Use 100% generated free electricity :: A 4eco Product

What is the minimum amount of export required for the immerSUN to start heating the water?

The immerSUN will wait for around 130W of export before any power is delivered to the immersion heater, once the water heating begins, however, the unit will be able control power in 1% steps, so for a 3kW heating element, the minimum power output is about 30W.

Our immersion element was replaced under warranty yesterday and from 10am onwards the ImmerSUN diverted 5kWh of power into the immersion rather than allowing it to be exported Our generation after 10am was 7.8kWh so we would have otherwise exported 64% of our generation. The tank didn't reach 60C (or 45C which is the boiler control thermostat setting) but considering it was completely cold at 10am after being refilled I'm pretty happy with the first day's result. The boiler kicked in at 6pm to top the temperature up to 45C. Grey dull day today so doubt we'll have much spare generation.

 

[sly_dog_jonah]

Hi There,

I have been looking at both the imersun and the sola controller but which would be best for my application?

I have a 4kw pv limited to 3.6 via inverter which reguarly runs for several hours at 3.6 when sun shines and hoping to install a 1 to 2 kw hydro system on a stream with variable flow rates giving a max input of 5.6kw. This will be all fed via 2 immersion heaters into a 300 litre thermal store. Although 5.6 is max it is unlikely to be achieved with 4.5kw being the expected max for most of the time.

Regen

Am not too familiar with the Sola controller but the ImmerSUN sounds suitable as it can power multiple loads of up to 3kW at any one time. Since your hydro will presumably run 24/7 you will probably have sufficient excess generation to keep your large thermal store permanently hot.

 

[goretex73]

I must thank everyone for their comments on this thread. I saw the immersun offered online and have been in touch with the company that installed my PV system is it right that you need to be a qualified spark to fit this or is this unit a job for the home owner to do ? If it is a spark job anyone in the Manchester area ??

 

[Gavin A]

We're installing a unit in preston on Wednesday, so could come across to Manchester after that, if we could get a unit in time.

 

[MicraShed]

it right that you need to be a qualified spark to fit this or is this unit a job for the home owner to do ?

I qualified in electrical engineering back in the 80's and I wouldnt dream of installing this myself.
Its not overly complicated when you look at the wiring diagram, but I imagine it will need a P cert.
I would rather do a couple of extra shifts at work and pay someone and know its safe and my house insurance will pay out in the event of anything going wrong than chance it to save a few quid.

 

[Sunshine777]

Yes Sly, Its been averaging 3.3kw hours per day for the past 32 days.


By this comparison, either the gas boiler is very inefficient or the calculation of the Immersun is somewhat inaccurate? I must say that using recognised formular to calculate the heat required to raise the amount of water in my tank seems to indicated that I need more kwh's than the Immersun indicates!

Any more thoughts on the accuracy of the Immersun's reporting?

 

[Martyfox]

Does anybody have any good data on Immersun running in real life, including import/export over a decent length of time?

Using a TRIAC, does the Immersun not import power some of the time, and export the rest, or have i misunderstood something... :6:

 

[Worcester]

@MartyFox

No, from a user point of view the ImmerSUN doesn't import any power EXCEPT if you use the overide timers or boost control. From a technical viepoint, it porportionally switches the resistive load on and off using burst fire. The electricity meters response criteria are such that they balance out the full power import / export over the very short period so they work just fine.

 

[series530]

I've built my own proportional control unit and am continuing operational trials at the moment.

It wasn't cheap but it gave me some experience of programming micro controllers and reading current and voltage using them. I also wanted a unit which gave me a wireless based visual indication of what was happening because the controller is far away in the garage. I suspect that, for somebody who wasn't bothered about the learning experience or the visual indicator, provided you know what you are doing, a unit can be built for about £70 without installation costs.

It's too early to say at the moment but, on a reasonable day, the system will heat a whole hot water tank for free so I suspect that it wont take long to pay for itself.

 

[Worcester]

@series530

Sounds good, can you share your ideas? So that others that want to spend the time and trouble building one for themseleves are able to follow your example.

For those that want to build one themselves, there is a fair bit of information, including step by step construction details and progarmming instructions, here: Home | OpenEnergyMonitor and specifically here: Solar PV Monitoring System | OpenEnergyMonitor and here: Labs | OpenEnergyMonitor (see the section entitled, Solar PV to Immersion heater control.

I know that one is very well researched - would be interested to see photos ond diagrams of how yours works.