Choice of intelligent switches ?

nobby1963

Hi All,
I have been watching the wrong thread and waiting for Immersun comments from those who have had it installed.
Just read the thread to date ( as best I can as I really don`t fully understand the `techie` stuff ).
Can I just ask what prices were paid all in - supplied & fitted ?
as I am in Devon my options are a little limited as far as negotiations go but it would be good to be armed with as much info as poss.
Glad to see it seems to be doing `what it says on the tin` and also glad I did not go down the EMMA route as it was getting close.
Cheers..

[Deleted User]

After investigating all the possibilities to further reduce our electricity consumption, including E7 tariffs, I've decided on the immersun. Just going through the process of installation quotes now

E7 would not suit us as nothing is on during the night bar the fridge/freezer nor would I want any appliances on during the night.

Whereas the immersun would make best use of the solar purchase already made. As we use a fair amout of hot water this would appear to be the way to go. Being at work during the day means it not possible to make best use of the solar. Having the washing machine on a timer for when I think it will be sunny is merely a nod in the direction of making best use.

Certainly better than the pitiful 3.2p paid for export.

Edit: If the system lasts longer than the FIT payments the Immersun would still make the PV worthwhile.

Hobbo2006

nobby1963 wrote: »

Hi All,
I have been watching the wrong thread and waiting for Immersun comments from those who have had it installed.
Just read the thread to date ( as best I can as I really don`t fully understand the `techie` stuff ).
Can I just ask what prices were paid all in - supplied & fitted ?
as I am in Devon my options are a little limited as far as negotiations go but it would be good to be armed with as much info as poss.
Glad to see it seems to be doing `what it says on the tin` and also glad I did not go down the EMMA route as it was getting close.
Cheers..

I got Philip Long from Sunny Futures Ltd to install ours. £420 including VAT, although I did arrange for 2 installs in the same street to get that price. I think his usual price is £450.

Performance has been as expected, although yesterday was a write off. Currently averaging around 3.6kWh's per day so far. I'd made my decision based on 1095kWh's per year at 12.5p each, as we only use electricity for hot water. obviously most of the saving will come in the summer so waiting with interest to see what happens during winter time.

I did find one drawback which is that the Immersun changes the waveform of the electricity which means that our existing energy monitor, a wattson solar plus, doesn't record the readings correctly. It still show the usage tracking the generation but seems to count the Immersun usage twice, meaning that it read more import than the meters show. I've contacted both Immersun and DIY Kyoto about this so hopefully they can rectify this.

Another slight issue is when to use the timed boost, in case the water doesn't reach full temp with the Immersun alone. The end of the solar day coincides with the use of the oven and the boost needs to cater for good and bad weather alike. I think that the timed boost would need to be changed 2/4 times a year to operate most efficiently.

All in all very happy so far. My neighbour gets a better yield from his immersun due to his panel orientation but as he uses gas to heat his hot water he can't claim the same payback period as ours. He's said he's very impressed by it though so there's two happy customers at least!

Why not come back and post an update when you've got some data from yours?

PS - We had an Immersion timer in place that wasn't needed when the Immersun was installed so that went on Ebay and sold for £19.50.... so I could include that in the figures!

nobby1963

Cheers Hobbo,
I will certainly post back when I get the system installed.
I just dont know if it`s best to hold off until next year now, will the price come down I ask myself & I know that it will give more `payback` when the sun is shining and thus waiting til next spring is tempting.
On the other hand I am sure any diverted PV generation will equate to a saving for us.
I will get on the phone and get some quotes ....
Thanks again Hobbo.

Hobbo2006

nobby1963 wrote: »

I just dont know if it`s best to hold off until next year now, will the price come down I ask myself & I know that it will give more `payback` when the sun is shining and thus waiting til next spring is tempting.

Perhaps get an installation late Feb. With generation of 460kWh's from Oct to end of Feb (for our set up) the Immersun will only save around 90kWh's (best guess based on anticipated generation/Immersun figures)..... if the price does come down then it's likely to come down by a greater amount than the saving you'll make from having the Immersun installed now.

Get prepared for the sunnier days of spring!

sly_dog_jonah

I've sent you a PM Nobby.

Just a note to others, make sure your quotes include 5% VAT not 20% VAT (when installed by the supplier) because the ImmerSUN qualifies for reduced VAT as it is a heating controller.

I've got some additional comments on top of Hobbo2006's observations:

• The device backlight can't be turned off unless the whole unit is switched off. Worth bearing in mind if the unit is visible in your house. The device's consumption is apparently <1W though.
• The daily kWh savings are calculated to 3 decimal places, but the cumulative savings and monthly savings are rounded down to the kWh. Therefore if you want to track the performance precisely you'll need to take a note of the amount saved each night (doesn't require any button presses as the display cycles through every few seconds).

Our OWL monitor (attached to import meter tail) reading is similarly affected by the ImmerSUN when it is dumping excess power into the immersion. I've checked our import meter though and it is not importing (LED permanently on) when the ImmerSUN is diverting power. However the OWL often reads in excess of 1kW as import/export (it can't work out the direction) when [Generation]-[ImmerSUN Load]-[Base load] is minimal (in fact export should be ~130W according to immerSUN spec). This peculiarity occurs whether the immerSUN power load is <3kW or 3kW (ie very bright sunshine, when export may still occur).

Stats from our first full 5 days (of very contrasting generation) with the ImmerSUN (all values kWh):

[FONT=Courier New]Generation     ImmerSUN savings      % used by ImmerSUN
10.3           5.050                 49%*
6.6            1.939                 29%
20.5           7.831                 38%+
1.2            0.000                 0%
4.7            1.288                 27%[/FONT]

Notes:
* 3kWh had already been generated when the ImmerSUN was first switched on, so ImmerSUN usage was actually 69%
+ Several times during the day the thermostat setting on the immersion was reached, so the unit display 'Water Hot' until we used more hot water.

orrery

Hobbo2006 wrote: »

I did find one drawback which is that the Immersun changes the waveform of the electricity which means that our existing energy monitor, a wattson solar plus, doesn't record the readings correctly.

This is one factor that has been bugging me about the Immersun...

If it controls the immersion with a thyristor or triac then the current is likely to be pulsed for only part of a waveform.

To put it simply: if there is a 3kW immersion and only 1.5kW of generation spare, does the Immersun pulse 3kW on for 50% (2 x 25%) of the waveform to get the 1.5kW? This is how a light dimmer would do it. If this is the case:
- can the inverter supply the current, or is some imported?
- how do the meters react?

sly_dog_jonah

orrery wrote: »

This is one factor that has been bugging me about the Immersun...

If it controls the immersion with a thyristor or triac then the current is likely to be pulsed for only part of a waveform.

To put it simply: if there is a 3kW immersion and only 1.5kW of generation spare, does the Immersun pulse 3kW on for 50% (2 x 25%) of the waveform to get the 1.5kW? This is how a light dimmer would do it. If this is the case:
- can the inverter supply the current, or is some imported?
- how do the meters react?

When my ImmerSUN is dumping excess power to the Immersion, the Import meter's LED stays on (indicating either zero import, or more likely, slight export).

sly_dog_jonah

Updated statistics after two weeks:

[FONT=Courier New]Generation     ImmerSUN savings      % used by ImmerSUN
10.3           5.050                 49%*
6.6            1.939                 29%
20.5           7.831                 38%
1.2            0.000                 0%
4.7            1.288                 27%
14.5           4.679                 32%
6.2            2.426                 39%
15.2           3.225                 21%
6.4            2.566                 40%
18.1           8.462                 47%
5.0            0.961                 19%
10.4           3.842                 37%
9.0            3.926                 44%
13.9           5.879                 42%[/FONT]

Notes:
* 3kWh had already been generated when the ImmerSUN was first switched on, so ImmerSUN usage was actually 69%
Several times during the high generation days the thermostat setting on the immersion was reached, so the unit displayed 'Water Hot' until we used more hot water.

The immersion thermostat was set to around 60C but I don't really trust it (I think it reads higher than the temperature actually is), so I've now raised it to it's maximum (80C according to the manufacturer) to see just how many kWh we can divert on a good day (5kWh generated already today, half of which has gone into the tank and the washing machine has probably used most of the rest). I've recently fitted a cheap pipe thermostat which should give some idea of the actual temperature, but this hasn't exceeded 45C in the past few days. The thermometer may be reading low though.

We have not yet adjusted the boiler program which heats water to 45C for 1hr each morning and evening. This only happens if the tank isn't hotter than 45C. There is usually scope for the ImmerSUN to heat at least 2 shower's worth of hot water a day (taken in the morning after the boiler has topped up to 45C if needed), and on good days the boiler doesn't need to fire up in the evening. Nipper's evening bath usually means the boiler fires up in the morning first thing though.

It's hard to quantify gas savings yet because the colder weather means we've had to put the gas central heating on several occasions over the past two weeks. I had hoped our first few weeks of results would have required no central heating, so allowing a comparison with 'summer' gas usage where hot water was the only gas usage. Comparing with the two week period last year is also difficult due to seasonal variation affecting whether we needed to have the central heating on (and how long it stayed on for). Since the ImmerSUN has been working, we've used 190kWh of gas (13.5kWh/day) which is almost identical to our 'summer usage' so the ImmerSUN appears to have offset the cost of the central heating being on for a few hours here and there. [By comparison, our Gas usage in early Feb last year was 84kWh/day, late Oct 49kWh/day and January 60kWh/day.]

In terms of electricity usage, the ImmerSUN has used 52kWh out of 142kWh generation, or 37% which would have otherwise been exported. The difference of 90kWh was either used by other household consumption or was exported when the tank was hot. The benefit of 52kWh of hot water heating means we've saved at least that in Gas, but almost certainly significantly more due to the inefficiencies of heating water via a boiler. 52kWh is around £2 worth of gas (ignoring discounts and standing charges), but as I say the inefficiencies probably put the savings at around £3. That's by no means a stellar saving (~£6/month) but given that generation is fairly low at this time of year I'm quite optimistic for the long-term. There's also plenty of scope for tweaking the boiler programs and thermostat settings to eek out better results. Of course we are also reducing our carbon footprint by using electricity to heat the water instead of gas.

nobby1963

Just to say we `bit the bullet` and had an Immersun unit installed yesterday by our local `ish installer in Launceston SJ Yeo.

Not the easiest instal for them as it transpired that we had on our immersion circuit not only our alarm system that we knew about but also our central heating system as well !

Now enjoying the benefits of not having to fire up our oil fired heating to get hot water ! - either that or cloud watching when turning on the electric to heat the water ( and that`s been hard with all the clouds we have had down here recently I can tell you ).

Seems to be doing as expected today & the suns shining too !

Nobby.