PV immersion heater proportional control

[methley]

Yes it is. In the photo above you can see it is feeding 647W into the immersion. It works by keeping the export between 30W and 70W wherever there is an excess being generated. It will work with any sized resistive load up to about 5.5kW. At the moment it's driving the immersion but will shortly have a couple of towel radiator elements hanging off it too.

 

[Scobo]

Excellent job !
Could I ask how much the parts cost ?

 

[methley]

Around about the £120 I would have thought.

 

[Scobo]

Not bad !
Give us a shout if you ever decide to market it. :wink_smile:

Scott.

 

[sly_dog_jonah]

I can now give an update to the Immersun device I have been testing. The device has exceeded my expectations and can report after a month of testing that it does everything it says in its specification.

Sounds very encouraging results. Our Immersun is getting installed Wednesday. Currently we have the gas boiler programmed to heat water for 1hr in the morning and 1hr in the evening, with the thermostat set to 55C. The 3kW immersion is at the bottom of the 200litre tank (new build so well insulated, 1C loss per day) but was until now just a backup in case of boiler failure. Once the Immersun is installed the initial plan is to keep the boiler programmed, but only for the evening in case it's been a rubbish day, but to reduce the thermostat to 45C and to set the immersion thermostat to be 55C.

After a while of testing that out, the next stage will be ramp up the immersion's thermostat much higher, to increase the energy we can dump, but to fix a blending valve to mix down the hot water to a safer 50C or so. This should reduce the probability of needing to 'top up' with gas heating, and also solves our issue of having our thermostat too low currently to prevent Legionnaires (because we have a toddler in the house and another on the way).

Throughout all this we will monitor the gas usage to monitor the effectiveness of the Immersun as well as tracking how many kWh it dumps into the tank. Hopefully it will be at least another month or two before the central heating (gas) has to be put back on, prior to then our gas consumption will be solely for water heating (and will hopefully be negligible).

 

[brian wright22]

Quote Sounds very encouraging results. Our Immersun is getting installed Wednesday. Currently we have the gas boiler programmed to heat water for 1hr in the morning and 1hr in the evening, with the thermostat set to 55C. The 3kW immersion is at the bottom of the 200litre tank (new build so well insulated, 1C loss per day) but was until now just a backup in case of boiler failure. Once the

Read more: http://www.electriciansforums.net/p...ter-proportional-control-6.html#ixzz25Oudjnnx​

Yes, the only downside to me setting the immersion heater thermostat hight to 65 degrees C is the very hot water I like the idea of a blending valve.Fortunately we don't have full time youngsters in the house only visiting Grandchildren which we can keep an eye on.

 

[sly_dog_jonah]

Yes, the only downside to me setting the immersion heater thermostat hight to 65 degrees C is the very hot water I like the idea of a blending valve.Fortunately we don't have full time youngsters in the house only visiting Grandchildren which we can keep an eye on.

If anyone has both hot and cold water pipes near to each other in the airing cupboard, and sufficient pressure for each then a blending valve should be a relatively trivial job for a plumber to fit.

I look forward to comparing results with you Brian. Do you have any estimate of the Gas kWh's saved in the first month?

 

[brian wright22]

I look forward to comparing results with you Brian. Do you have any estimate of the Gas kWh's saved in the first month?

So far I have managed to get enough hot water to enable the Gas Boiler to be turned off for 32 days since the installation of the Immersun. It also depends on the total size of the hot water tank and the depth that the immersion heater (Top Mounted) extends down into the tank.Ours is 1050 mm high and the immersion heater is 36" in length. Hence it does heat virtually down to the bottom of the tank which gives about 130 litres capacity. The tank is rated at total water capacity of144 litres.
The savings in Gas over the 32 days is @ 3.556pence/kwh x average gas consumption x 17.6 kwh = about 62.6 pence per day to heat the water. There is a 21p / day standing charge but I have to pay this anyway so this is not included in the calculations.
Multiply this by 32 days so far = £ 20 total gas saved.
Obviously it won't be as high as this in the winter months but there will be a saving.
I have attached the installation shot. I'm trialling this device and found the MK grid switches very conveinient.

 

[sly_dog_jonah]

Thanks for the information Brian. Our 200 litre tank is 1.45m tall, but the immersion is positioned around 35-40cm from the bottom so there is plenty of water above the element to heat (about 150 litres by my reckoning). It's only a 13" element but I don't think this should affect things too much as it is horizontally mounted in the tank.

It's a shame 'No Standing Charge' tariffs are few & far between these days, otherwise we could eliminate that pesky 21p/day during the warmer quarters of the year (assuming you don't cook with gas).

 

[brian wright22]

Yes we do cook with gas so its not all wasted!!

 

[yorkshiremike]

Brian, do you think your 17.6kWh of gas saved daily is a bit optimistic? For example, how many kWh has your Immersun indicated that it's putting into the HWC each day? The reason I'm asking is that I'm wondering how inefficent (in terms of gas energy to energy in hot water) the indirect gas water heating is. Certainly a modern condensing combi boiler can manage 80%+, but it is directly heating the water so I was sort of assuming that a modern condensing system boiler would be making 70%+ after allowing for heat loss in pipes to the HWC etc. But this would still mean that 17.6kWh should be more than enough to fully heat the HWC from cold twice a day. Energy to heat water in Wh at 100% efficiency = 1.16 x number litres x temperature rise, so 130 litres through a 35 deg temp rise = 5.28kWh. The immersion should be close to 100%.

Mike

We've fitted several Immersuns now, though a couple of the customers needed rewiring as they had other stuff connected onto the immersion circuit. I've one fitted at home, but it is only heating a towel rail - we have a combi - currently planning to have a thermal store fitted, unless anyone has a better idea.

 

[sly_dog_jonah]

I went through some very similar calculations yorkshiremike when weighing up whether to invest in an immersun. I think Brian must be basing his calculations on reduced gas usage, not the amount dumped into the immersion by the immersun. But I'll let him answer your question.

Our hot water usage via a modern Gas boiler (non-combi) averages 13/14kWh/day for 1 shallow bath (for a toddler) and 2-3 showers/day. Our dishwasher and washing machine both have cold supplies only. The tank's thermostat (for controlling the boiler) is set to around 45C. Since we have a large tank I'm hopeful that sufficient heat will be retained from good PV days even if they are followed by rubbish days, and negate the need for any gas water heating except for during poor weather spells. However I'm realistic and expect that on most days of the year we'll have to use some gas, but less than we currently do.

 

[brian wright22]

Brian, do you think your 17.6kWh of gas saved daily is a bit optimistic? For example, how many kWh has your Immersun indicated that it's putting into the HWC each day? The reason I'm asking is that I'm wondering how inefficent (in terms of gas energy to energy in hot water) the indirect gas water heating is. Certainly a modern condensing combi boiler can manage 80%+, but it is directly heating the water so I was sort of assuming that a modern condensing system boiler would be making 70%+ after allowing for heat loss in pipes to the HWC etc. But this would still mean that 17.6kWh should be more than enough to fully heat the HWC from cold twice a day. Energy to heat water in Wh at 100% efficiency = 1.16 x number litres x temperature rise, so 130 litres through a 35 deg temp rise = 5.28kWh. The immersion should be close to 100%.

Mike

We've fitted several Immersuns now, though a couple of the customers needed rewiring as they had other stuff connected onto the immersion circuit. I've one fitted at home, but it is only heating a towel rail - we have a combi - currently planning to have a thermal store fitted, unless anyone has a better idea.

Yes it is the amount of Gas in kwh that I am not using by having the Gas central heating boiler on water heating only.This was based on the gas bill from EDF over the period of time that the boiler was not used for the Central heating.
The thing to remember here is that the Gas boiler loses a significant amount of heat through its casing anf the 1 inch pipes that feed the tank indirect coil.It was originally thermo syphon but is now fully pumped but not a condensing boiler.
With the Immersion heater every bit of power goes into heating the water.
From my EDF Gas Bill, the meter is measuring the gas by cubic M, this is then converted to Units and the value equals Kw/h with a calorific value of 38.4. Whereas the electric bill quotes the Units are equal to Kw/h.The units of Gas does not equal units of Electricity
I hope this helps

 

[brian wright22]

I went through some very similar calculations yorkshiremike when weighing up whether to invest in an immersun. I think Brian must be basing his calculations on reduced gas usage, not the amount dumped into the immersion by the immersun. But I'll let him answer your question.

Thanks Sky, you are correct it is based on my reduced gas consumption.

 

[sly_dog_jonah]

Brian, The Immersun can display it's daily/weekly/monthly/lifetime kWh's delivered to the immersion: Main Menu>View Savings then cycle through the time periods). 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).

http://www.immersun.co.uk/downloads/immerSUN Installation and User Guide v1.0.pdf Section 5.4

 

[brian wright22]

Brian, The Immersun can display it's daily/weekly/monthly/lifetime kWh's delivered to the immersion: Main Menu>View Savings then cycle through the time periods). 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).

http://www.immersun.co.uk/downloads/immerSUN%20Installation%20and%20User%20Guide%20v1.0.pdf Section 5.4

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!

 

[pwboston]

I have dual immersion as only source of heating hot water, on E7

so i can easily tell each day what my water took to heat it. currently using between 4 and 8kw per night at 6p per unit to heat my water, so my savings wont be that huge, and its a lot harder to guage what gas or oil would be saved, but this system does give an accurate saving on electric (if i installed one)

 

[pwboston]

Incidentally with this being a fit after an install job does it still come under the 5% VAT?

 

[brian wright22]

Incidentally with this being a fit after an install job does it still come under the 5% VAT?

Very interesting question. Immersun are certainly adding 20% vat!!! via their suppliers. If it does qualify for a 5% vat then they are making a 15% extra profit.

 

[yorkshiremike]

By its self, it doesn't qualify for the 5% rate (see HMRC site):
[h=2][/h][h=2]The reduced rate applies to installations of:

• controls for central heating and hot water systems (see paragraph 2.6);
• draught stripping (see paragraph 2.7);
• insulation (see paragraph 2.8);
• solar panels (see paragraph 2.9);
• wind turbines (see paragraph 2.10);
• water turbines (see paragraph 2.11);
• ground source heat pumps (see paragraph 2.12);
• air source heat pumps (see paragraph 2.13);
• micro combined heat and power units (see paragraph 2.14); and
• wood-fuelled boilers (see paragraph 2.15).

[/h]


If you argue that it is ancillary to fitting PV and the Immersun is fitted at the same time it's possible that it should be 5%. So far, we've just fitted for existing customers who have already had PV, so charged at 20%. If the bill you get shows VAT, then the legally the rate shown is what they have to account to the Tax man at.

 

[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.