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Solar Diverter

  • 10-09-2021 6:50am
    Registered Users Posts: 2,679 ✭✭✭

    I am waiting on my PV install - and have opted to NOT include any diverter for the initial install. I would like to get one - BUT I have no immersion currently, and only need a solution during summer really. During winter my OFCH will heat the water anyways.

    I would get a diverter IF i thought it would be totally automatic and just heat water during summer. BUT from my research it isnt all that easy to do what i want...

    1. only some of them are programmable i think... i dont want something that is "dumb".
    2. i dont want to have to hit a "boost" button to heat the immersion - i want always hot during morning showers and evening cooking times only.
    3. I have a battery. I want a diverter that will not be "last in line"... will work off the excess OR the battery if the schedule demands it. I think most only sense the system exporting to grid - and work during that time.

    Does what I want exist at a reasonable cost?

    Also any rough idea what it would cost to retrofit an immersion as I dont currently have one?

    Or am i wasting my time here - just burn the oil and forget it.


  • Moderators, Sports Moderators Posts: 17,886 Mod ✭✭✭✭slave1

    Given you do not have an immersion currently you are looking at €1k plus for both insulated dual coil hot cylinder and diverter.

    Financially speaking, does not look good

  • Registered Users Posts: 475 ✭✭idc

    Not sure what Diverters your looking at but the both the Eddi and iBoost have timer functions. If you have a hybrid inverter with a battery that will always take precedence over anything else using surplus, but the timed boosts of both the eddi and iBoost will operate like any other appliance during the boost and draw from PV/Batteries or grid depending whats available.

  • Moderators, Home & Garden Moderators Posts: 4,439 Mod ✭✭✭✭graememk

    Cost wise, you'll never make it back.

    But running though a few things

    Do you currently use the oil on a timer and it only heats the hot water?

    Oil will still be cheaper than using the immersion when there isn't excess solar (ie the mornings) the oil still could boost it in the evening too as needed.

    Fitting an immersion depends on your tank, if it doesn't have a place to put one in, you can use a Willis, external immersion.

    I'd wait and see how much excess you'll have before changing anything.

  • Registered Users Posts: 791 ✭✭✭reklamos

    I would agree that diverter is not a good investment for you since you want hot water when there is not enough sunlight even in summer. It is possible to to achieve all you want with diverter and inverter settings. You can set timer on diverter to heat water and/or you can also set timer on inverter to discharge or limit charge battery which would allow the diverter to kick in. One thing to note though I would avoid heating water from battery as this will impact the life of the battery.

  • Registered Users Posts: 2,215 ✭✭✭bullit_dodger

    One thing to note though I would avoid heating water from battery as this will impact the life of the battery.

    Why? Batteries have 1000's of cycles available and the leccie doesn't care if it's going into your kettle or an immersion heater coil :-) You bought the battery to give flexibility and options of using solar (or cheap night rate) captured energy. I'd have at it, it's doing the very thing you bought it for !

    Course what you don't want, is to be using the battery in early AM, which has units filled from night rate. In that case you would be better off eliminating the losses and grabbing the energy from the grid directly - but yeah, if the battery had units captured from solar the day before.....crack on.

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  • Registered Users Posts: 2,679 ✭✭✭yankinlk

    Thanks all! I will leave it out. SOmeday ill replace the OFCH and im sure it will be here i come to get the advice!

  • Registered Users Posts: 791 ✭✭✭reklamos

    Batteries do care if you charge/discharge them at full throttle or half throttle. If you look at battery manual you'll most likely see that there are recommended(0.5C), max(1C) and peak(>1C) charge/discharge rates. Charging/discharging at high Amps will degrade battery faster. I've seen somewhere stated that 6000 cycle on pylontech are only achieved when using battery at 0.5C, with 1C the cycles drop to 4500.

    I have been monitoring my batteries for a while and noticed that on high discharge rates the cells get out of balance much easier. And it does take a while for them to balance out.

  • Registered Users Posts: 2,215 ✭✭✭bullit_dodger

    To be fair, your dead right, a hard cycle isn't as kind to them as a trickle discharge. Same on the charging side too. Better to slowly charge them (if you can) over dropping 50A on them. While I understand the concepts of the top/bottom balancing, I wouldn't class myself an expert there.

    But my main point is an Immersion coil isn't going to be much different from a kettle, a washing machine or a tumble dryer. Most of those devices drawing down ~2kw to 3Kw, which is the max discharge rate of a lot of batteries. Yeah some batteries will do more, and of course you could paralleled them to give you a greater max current....but for most cases something like a washing machine will get you to max discharge rate. A immersion coil isn't much different - so I'd "have at it".

    Otherwise it becomes a question of, "Do I want to stop all heavy hitters from touching my battery?" Not just immersions, but washing machines etc. Yeah, it will last longer, but it's sort of defeating the point of why you have a battery to begin with. They won't last forever - hopefully long enough to pay back the cost, but I think it's a good use of why you bought it.

    Post edited by bullit_dodger on

  • Registered Users Posts: 791 ✭✭✭reklamos

    I agree that the load of these devices can be similar. It boils down how long you are using them. Kettles can be 2-3kW and takes 2-3 mins to boil water. Washing machines and dishwashers are 2kW and again from my logs only run up to 15mins max. A tip for everyone, know when your washing/dishwasher is heating water so you do not max out your system.

    The immersion heaters again come in all shapes and sizes but normally it is 3kW but unlike your kettle it will take more than 3 mins to heat up that water. Also bigger cylinders come with 2 heaters.

    As for the question of, "Do I want to stop all heavy hitters from touching my battery?" the answer is still yes but I want to be smart about it and minimize as much as possible. I agree that we have invested in the equipment and should use it but to get the best out of it you need to be smart on how you use it.

    Anyway I think I went off topic here. Sorry about that. :)

  • Registered Users Posts: 9,934 ✭✭✭the_amazing_raisin

    I'm not really getting the point of having a diverter running off the battery, seems like juggling energy around

    Seems like a better investment to get a well insulated tank and just heat the water when it's free. It'll help make your oil heating more effieicient too

    I'm wandering OT but I've seen some heat pumps can be run off a solar diverter, so they try to heat the water or house when the sun is shining

    If you're thinking of a heating upgrade in the future then it might be worth looking into it

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  • Registered Users Posts: 2,215 ✭✭✭bullit_dodger

    We may have to agree to disagree here. I do see what your saying - and please don't think I'm saying your flat wrong - your not. Not at all. We just different values about what a battery should be doing for you I think.

    A washing machine will probably only be at 2-3Kw while it's heating the water in the drum. A dishwasher though tends to be a bit harder in my experience. Like you I had a look at the current draw over time as there's a heating water phase and then at the end a drying phase. A tumble dryer would be the obvious worst offender as it tends to be high for a long period of time, although I see those new heat pump types are a more reasonable ~800W these days. Then you have irons , toasted sambo makers, let's not forget the oven(!) albeit the heating element won't be on all the time.....(or it shouldn't unless you've a very broken oven)

    Basically a whole host of things which could easily drop 2Kw which on top of your baseload will probably get you close to max discharge rate.

    For me, I've 2 heating elements in my immersion. A 2kw near the top and a 2.5kw near the bottom. They are never both on at the same time. "Sink" takes about 10 mins to heat the water and "Bath" about 35 mins in a 150L tank. Rough times which of course will depend on ambient temps etc.

    What your saying is right, but I think in the general context that if your not worried about those other things many of which have similar loads & durations, then I probably wouldn't single out an immersion. Batteries don't "like" it, but they'll handle it without too much negativity.

  • Registered Users Posts: 2,215 ✭✭✭bullit_dodger

    I guess it depends on where and when you got that energy that's in the battery. If you took it from night rate, and your using it while still in night rate - then that's a bad move. Your losses would mean your losing money. However, if the energy was something that you put into the battery during the previous days solar production - good use of a battery I think. I've good insulation on my tank (2x lagging jackets) and after 24 hrs, it still feels luke warm (not hot) to the touch. Probably won't need to "heat from cold"

    Overall though to go back to the original point of the topic "Solar diverter", personally I'm for them on the grounds of flexibility and convivence. Not sure there's a realistic "break even" timeframe, but man ..... there's a lot to be said for having hot water readily available 7-8 months of the year!

  • Registered Users Posts: 2,679 ✭✭✭yankinlk

    was listening to a pdcast recntly (REvisionist History s06e08) about Laundry and also (stuff you should know episode) and how we dont NEED hot water to wash stuff, dishes or clothes. If you buy good washing detergents, they are made to use cold water best! Very intersting - altho i admit it aint me that does it :P

    My house still uses a lot fo leccy - i recons its the 3 young gamers mostly.

  • Registered Users Posts: 791 ✭✭✭reklamos

    As with everything solar. There is plenty of it when you don't need it. During good periods this summer I had trouble using all the hot water during the day and that is with 10kWh battery being 100% charged. I think heating water from battery is just false economy. If I needed to have hot water all the time from solar I would just limit battery charge rate and then diverter would do the rest but would not charge from battery. I also want to have hot water in the morning and for that I just use automation which turns on the boiler each morning and heats the water to specific temperature. If the water is still hot enough from last day then nothing happens. It is cheaper to heat with gas. I only have diverter to heat water so I do not give it away for free when there's electricity more being generated than I can use or charge. This keeps my exports to minimum. In over 2 years I exported just 220kWh.

  • Registered Users Posts: 3,306 ✭✭✭John.G

    The OP has PV solar so he would require a electric immersion and not a coil but still no pay back IMO especially since he has a battery.

  • Registered Users Posts: 2,215 ✭✭✭bullit_dodger

    LOL - 3x young gamers!

    I've an Nvidia 3090 graphics card. Damm thing sucks down ~400 watts at full pelt. That's unusual tbf, most GPU's are in the 150-250W range for just the card, not the CPU or anything else! I presume xbox/PS5 are of similar ballpark....most of it comes off as heat.

    On the plus side, I don't have to turn on the central heating when I'm gaming. So it's not all bad..... ! :-)

  • Moderators, Home & Garden Moderators Posts: 4,439 Mod ✭✭✭✭graememk

    Yeah.. I said that?

    "Fitting an immersion depends on your tank, if it doesn't have a place to put one in, you can use a Willis, external immersion"

    A willis doesnt use a coil, its takes cold water from the bottom of the tank, and heats it and puts it in the top.

  • Registered Users Posts: 9,934 ✭✭✭the_amazing_raisin

    Yeah I did have a good laugh at that idea, gaming PC's and consoles don't use a huge amount. Basically anything that involves heat or moving something heavy is the biggest power consumer

    Case in point, my house is heated by an air source heat pump, all electric cooking and 2 EVs. Current consumption is around 12,000kWh per year, nearly 4 times the national average

    Ironically it does work out cheaper overall because of the efficiency gains. I also have the advantage that I can use solar for all my energy needs. No tricky stuff of mixing energy sources like the OP

  • Registered Users Posts: 3,306 ✭✭✭John.G

    OK, someone mentioned a dual coil cylinder so I mistakenly thought you meant the Willis external heater with a (solar) coil which they also do or did make.

  • Registered Users Posts: 1,827 ✭✭✭randomname2005

    On the same idea, but with an immersion, what would be the cost of retrofitting a diverter

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  • Registered Users Posts: 2,679 ✭✭✭yankinlk

    Gaming PCs dont use a huge amount.... yeah they do especially when you have a house full of gamers. my annual consuption is not far off yours.