Advice on Hot water Tank & iboost (or similar)

theboylard

And obviously the sums differ depending on which solar diverter you buy - Immersun are not cheap, iboost cheaper but not by much.

Mine (solarimmersion) cost £180 and was fitted for nothing. Does'nt have pretty info telling what's been transfered, but no biggie.

legoman62

Mine cost about £90.00 inc a 1kW immersion.

I used energysavingexp's excellent idea and have run it for over 3 years:D

You need some DIY skills but hey, I did it;)

Using Wattson, I can see when I'm diverting power to the immersion:)

Heedtheadvice

Let me reiterate the need to consider how much might be saved at what might be the installation cost

Do you need a new cylinder, say £200, immersion heater £20. No existing wiring to a heater, say £50 assuming there is provision/space at the fuse box and then the 'boost' or 'sun' and installation say £ 250 to £350. Not definite cost but you can buy a lot of gas for that amount .
These units (as far as I know) come more into their own when using your excess generation to replace an expensive fuel. However bear in mind that they can also provide power to some electic heaters too and those might be usefull in spring and autumn when generation is reasonably high.

pinnks

I wouldn't disagree with the above but another thing to take into account is the losses in probably unlagged pipes between boiler and tank. My return run of pipe is about 20m of 22mm and 28mm copper. Boiler is new but pipework from the mid 80s and not lagged under the floors.

I have 3 summers behind me now with my immerSUN and have saved about £80 a year in gas (boiler turned off) when compared with earlier years' records, which I have been keeping for 6+ years now. Over the remainder of the year I save a few quid more (maybe £20) pre-heating the water on half-sunny days, leaving the GCH to do the rest. I have set the immerSUN to record at leccy rates which shows I have saved about £200 (July 2013 to Sept 2015) via the immerSUN.

So, gas saving over that period £240 to £280 or so, or diverted at leccy rates £200. Either way I am happy with the return to date.
HTH

Gary

Heedtheadvice

So based upon your practical data, Gary, it would seem to be a good proposition and give quite a good payback period.
Could you give some more info regarding availability of hot water such as roughly how much you might use (say family size, do you have showers or baths, is hot water used by any appliances etc.). We have our gas on quite early in the morning to ensure hot water first thing. I note you have primary panels WSW so what typically is the start time in the morning for excess production that would be used for water heating?

It might also be of value if others too can post their practical experience of these add ons.

:beer:

pinnks

Where to begin...

First there are now 2 of us and we shower. Historically we had the water and heating on at the same time and left the timings the same all year. Something like 6-8am and 4:30-9:30pm. Not sure when the water would have been actually heating during those periods when the heating is off in the summer.

Our tank is a normal size (200l?) copper tank with about 2.5cm insulation from the early 1980s. I have added a blanket which was worth the £10 or so. As long as the water is heated to hot we can actually last the following day (just) before it all gets a bit cool-warm, so if sunny one day and appalling the next we do not need to boost the system. I guess that means you might supply a family of four on a normal day.

No hot water used in appliances but quite a bit used daily for rinsing off dishes and so on.

WSW panels are rubbish in the morning, which is one reason I added the second system. Until the panels come into direct sunlight at lunchtime we get a couple of hundred Watts. As soon as they get direct sunlight it jumps to 3kW. You need to cover your base load (few hundred Watts) plus 50W before the diverter cuts in and then of course need a reasonable excess before diversion is worthwhile - the energy has to be there to heat the water - so the WSW panels alone only provide water heating from midday or so but that was not a problem in terms of morning showers.

Now I have the second system the water is normally back to temp by late morning following morning use. The afternoon then just keeps it that hot with the odd top-up.

If the water is not hot by sundown you can get the immerSUN to run the immersion at full power for 15 minute (750Wh) periods, so you can work out how long to run it to top-up. I may have to do this 3 or 4 times at the start/end of the gas-off period.

Today we generated just over 6kWh, cover base load for much of the day and a mixture of washing machine and diverting to hot water and some to space heating once the water was hot. There was some importing for the washing machine as clouds came over but surprising to get both things done - washing and hot water at this time of year

Heedtheadvice

Thanks for that report and you obviously have some good reasoning behind your system and it's use.

We have a more modern tank, supposedly well insulated, but not as thick as you mention, approx 10mm. From gas heating we currently have a similar heating cycle to yours (and consumption I guess but with a power shower) and find we need the morning boost so expect our losses must still be highish. For efficient use of any available diverted heat during the day I think I will invest in more insulation -after all the airing cupboard is always plenty warm enough!