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Immersion Diversion

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Hello again from "The We*t Country" :)

Could I please have some learned comments ( you all know who you are :) ) on why a Immersion, or iBoost etc. is required, when
I am at home all day, can see when the sun is out, and only a fridge/freezer is using a few hundred watts, so I can just turn on the immersion myself, or plug in an oil-filled radiator, or even switch on an induction hob (as suggested by silverwhistle) ...

So what is the point in spending a few hundred pounds to do this ?

or am I missing something, again ? (surplus brain cells for instance)
16 x Enhance 250w panels + SolarEdge Inverter + TREES :(
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Comments

  • Sterlingtimes
    Sterlingtimes Posts: 2,521 Forumite
    Part of the Furniture 1,000 Posts Name Dropper
    At time intervals where where is insufficient solar power generated to power both the normal electrical load and the immersion, you would import expensive electricity unnecessarily from the National Grid.

    It is unlikely that you would do a good job at switching on and off the immersion over the course of a day by doing the controlling manually.

    The iBoost or similar achieves real time management ensuring that the gas is replaced by solar generated power only when it is cost effective to do so.
    I have osteoarthritis in my hands so I speak my messages into a microphone using Dragon. Some people make "typos" but I often make "speakos".
  • EricMears
    EricMears Posts: 3,304 Forumite
    Part of the Furniture 1,000 Posts Name Dropper
    Note also that you'd only be able to switch your immersion heater ON or OFF. These devices adjust the power drawn by the immersion to exactly match whatever surplus power you have.
    NE Derbyshire.4kWp S Facing 17.5deg slope (dormer roof).24kWh of Pylontech batteries with Lux controller BEV : Hyundai Ioniq5
  • DREKLY
    DREKLY Posts: 213 Forumite
    Tenth Anniversary 100 Posts
    Aha, thanks Eric, I was not aware of that, thought it would just connect up, and try to send 3KW (the immersion rating) which of course, may not be generated all the time, during a good day
    in the peak hours 11am to 3pm - ish.

    Originally, the install company agreed to include an "Immersun"
    (in writing, on the signed contract !), but since an upgrade in
    the type of panels, because of tree shading, the salesman has
    said it won't be supplied, is unnecessary, etc. etc.

    I am not too impressed with that....
    16 x Enhance 250w panels + SolarEdge Inverter + TREES :(
  • DREKLY
    DREKLY Posts: 213 Forumite
    Tenth Anniversary 100 Posts
    SterlingTimes, it is an all electric property, but I assumed that just
    having the immersion on during a good sunny day, for a couple of hours, would be enough to get a reasonable tank of hot water, free..
    It's a top loaded immersion in a 3ft x 18" lagged tank.
    But I also planned on running a 400W background panel heater, and
    perhaps a 1Kw oil radiator when output is sufficient, but I get your point, the LAST thing I want to do is import that power during daytimes ! cheers.
    16 x Enhance 250w panels + SolarEdge Inverter + TREES :(
  • pinnks
    pinnks Posts: 1,548 Forumite
    Tenth Anniversary 1,000 Posts Name Dropper Photogenic
    How can the installer suggest an immersun is not needed when already contractually committed to?


    If you want to see the difference between the various diverters, from immersun's perspective visit their site and follow the link.


    Key differences seem to be compliance with regs etch, the initial switching watts and the immersun can power 3 devices, not 1.


    If you all electric, why would you not want a diverter?
  • ely_ellis
    ely_ellis Posts: 140 Forumite
    Part of the Furniture 100 Posts Combo Breaker
    edited 25 July 2015 at 6:36AM
    I am very new to the Solar game but I have gone into it in 'probably' over the top and in depth, but still learning.
    I have only had my install just under 1 month and I had an iBoost included. I get a full tank of hot water every day at the moment. There only 3 of us and we don't use the full tank every day so it's more of a 'top-up' heat, but it is hotter than we are used to. We are oil heated so normally stick the oil boiler on for a tank of hot water every-other day. So, not sure how much oil we are saving but its nice to have a full tank of hot water without having to think about it.
    As already pointed out, it varies the power to the immersion heater depending how much spare you are generating rather than the full 3kW of just turning it on.
    I have been watching mine closely and the amount of variation in diverted electricity would make it extremely impractical to do it manually unless its an absolutely crystal clear day where you can be sure a cloud is not going to drop your generation 10 seconds after you stick the immersion on.
    Not sure on exactly how much savings I will make over burning oil but the iBoost was in with the deal so in theory it didn't cost me anything so can only benefit.
    One more point but unsure of this one..
    On the iBoost there is a second set of contacts. I am a little unsure of how they work but from what I understand, when the tank is hot and the thermostat on the immersion heater cuts the power off, the iBoost shows tank is hot. I assume that at that point, the second set of contacts operate, but unsure if this is just an on-off contact or controlled like the first. Either way, that gives an option for a second lower (if you have) immersion element or something else that could store heat.
    Maybe someone could clarify this?

    EDIT:
    I have just read through the iBoost manual and it appear that the second set of contact are not controlled by the spare exported electricity and all they actually do is turn on or off the supply manually or timed regardless of generation.
    Pitty it was not as I assumed above, it could have been quite useful!
    End EDIT:

    Cheers
    Martin (With an I)
    Martin (With an I)

    4.00 kWp System, 15° East of South, 35° Pitch, 16 (250w) x 8.33 Eternity Panels, Solaredge Optimisers and SE4000(16A) inverter, iBoost. Just North of Gainsborough, Lincolnshire.
  • DREKLY
    DREKLY Posts: 213 Forumite
    Tenth Anniversary 100 Posts
    Hi, MartIn with-an-I ! interesting post !! that's why I wanted the immersun, because it seems you can control up to three devices via its switching... I shall still push for it, as it's written on the contract, signed by both myself and the salesman, but with different panels..
    ...watch this space...
    16 x Enhance 250w panels + SolarEdge Inverter + TREES :(
  • Sterlingtimes
    Sterlingtimes Posts: 2,521 Forumite
    Part of the Furniture 1,000 Posts Name Dropper
    edited 25 July 2015 at 10:52AM
    For an all electric property without Economy 7, the iBoost would be far more rewarding. But with Economy 7, the results could be marginal. Diversion to non-storable heating could be productive

    For me in a gas/electric property the results are far from encouraging.

    For gas displacement

    Since late November 2014 install solar energy diverted to the immersion is 588 kWh. That falls a long way short of fulfilling my hot water requirements.

    Efficiency of boiler for hot water only heating is 49.7%. I will add 5% loss for the short copper run from the boiler to the hot water cylinder. Efficiency therefore 44.7%.

    Gas saving is 588 / 0.447 = 1315 kWh.

    This prices on Ovo Better Energy inclusive of VAT as 1315 * .0304 = £39.89 saving.

    Loss of export earnings

    588 kWh @ £0.0485 per kWh = £28.51

    Overall saving in approximately 8 months

    £39.89 - £28.51 = £11.38

    PAYBACK is approximately 20 years (assuming that iBoost lasts that long).
    I have osteoarthritis in my hands so I speak my messages into a microphone using Dragon. Some people make "typos" but I often make "speakos".
  • pinnks
    pinnks Posts: 1,548 Forumite
    Tenth Anniversary 1,000 Posts Name Dropper Photogenic
    This is always an interesting calculation/discussion point. A couple of thoughts.


    According to the comparison page on immerSUN's website the iboost doesn't kick in until there is an excess of 500W. I have no idea if that is correct but I do know the immerSUN kicks in about 50-100W of excess power and always tries to leave that 50W buffer to ensure you don't import by mistake. You can customise that buffer if you want. This will make a big difference on typical UK days - while that 400W "extra" will only provide gentle heating it would at least stop further heat loss from the tank, so overall you should get more free hot water days. Make of that what you will as I have only an immerSUN, so can't verify the differences...


    I have had my immerSUN for just over 2 years and pushed about 1.5mWh through it. I get free hot water from mid-April to mid-October and on about 60% of the rest of the year. Calculating savings is interesting but I know from my records that by using no gas from over the summer months (boiler turned off) I am saving about 2,000kwH or about £80, so for me a diverter does pay for itself. One thing people seem to leave out of their guesstimates are the losses between boiler and tank - all that nice heat leaking from unplugged pipes under the floor.


    If you are electricity-only, then as others say, it seems a diverters is a must and I would certainly go for one with more than one proportionally controlled output to maximise own consumption. Why not visit each firm's website, download the user manuals and compare the pros and cons of each sort of inverter?


    Gary (also with a y), ho hum
  • ely_ellis
    ely_ellis Posts: 140 Forumite
    Part of the Furniture 100 Posts Combo Breaker
    edited 25 July 2015 at 11:27AM
    pinnks wrote: »
    the iboost doesn't kick in until there is an excess of 500W.

    After reading the iBoost manual, I realised it does not give any specifications or mention at what point the iBoost kicks-in.
    However, I had a look at the FAQ and it says it is set to kick-in at 200W.
    It was something I was wondering about too.
    I am more worried about when it shuts off rather than when it starts. If for some reason it doesn't stop when I stop exporting and continues importing, that would be costing me money that I wouldn't normally spend!

    Martin (with an I)
    Martin (With an I)

    4.00 kWp System, 15° East of South, 35° Pitch, 16 (250w) x 8.33 Eternity Panels, Solaredge Optimisers and SE4000(16A) inverter, iBoost. Just North of Gainsborough, Lincolnshire.
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