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Water "Battery" 20kwh+ of extra storage



  • Moderators, Home & Garden Moderators Posts: 5,758 Mod ✭✭✭✭graememk

    It's got cold, hasn't it?

    Was away for just under a week, maintained the temperature at 18c

    Didn't want to try to lift the house from cold when I got back.

    when it was mild, the 12kwh I was putting in it a night was fine.

    When it got cold, it wasn't enough. It never got ahead. (Charging at 3kw).

    So was able to run both immersions to heat the tank, that was able to get ahead. But used about 50kwh (would have been 6L of oil though!)

    Although by time night rate rolled around again, the house was at about 17c (and dropping) tank was also at about 20.

    Now that I'm home, the tank is heating the house in the morning. And also filling in the gaps when the fire dies down.(turf, from less than 2km away.. solar dried!).

    Last night 34kwh was put into the tank.

    Tank flow out temperature is set at 46c,

    If I put a heatpump in, (would be looking at a propane one, as that has a better cop at higher temperatures) a 10kw one should be enough for my house, would be plumbed straight into the buffer tank. Cop of 3 should be obtainable.

    Theorycraft, 100kwh of heat/day for nov-jan, 90 days.(no fire) 3000kwh of electric via heatpump vs 9000 using pure electric.

    9000kwh, put into perspective you wouldn't have much..if any change from 1000L of oil.

    House is lovely and warm. Occupants are not complaining 😆.

    This is mostly an eddi install, not sure if it's on a buffer tank or DHW, but someone is a crazy as me.. but with a lot more funds!

  • Moderators, Home & Garden Moderators Posts: 5,758 Mod ✭✭✭✭graememk

    As mentioned in another thread, and for the ones following (I'm not going to do a full install video a-la Gyln Hudson : ) worth a watch.

    I have a heat pump heating the buffer now, An ecoforest EcoAir+ 3-12kw. Its a R290 ones which can do 60+ for CH and 75 for DHW I think [ but at a cost of efficiency] Not the usual setup, but I'm tinkering with it. 1980's bunglow.

    I heat the buffer, buffer heats the house. Currently the HP kicks in at a 5c drop (in a 500L tank). Allows me to keep my current tado system.

    I have been heating to 60c overnight, precharging the tank, and the house before night rate ends. Last night was cold, it really hurt the COP, only about 2.4! Have been running the tank at 50c during the day these last few days but have backed it off to 46 today.

    Currently running it all on night rate or battery. These freezing conditions, the fire is still on, but majority of heat is coming from the heat pump now.

    The living room has been struggling to get up to temperature (without the fire). Rad is currently behind the sofa, with a bit of space but not great. It has never been an issue.. theres always been a fire, Never has been an issue before. While I did have oil, it wasnt used that much. maybe a blast in the morning/night I had never heated only by oil... Or my grandfather didnt either. Radiators have all been changed since the house was built, mostly double radiators now.

    Living room radiator is possibly undersized. Going to experiment with radiator fans. More experimentation!

    Follow along! : (room temperature is buffer temperature)

  • Registered Users Posts: 238 ✭✭AmpMan

    Am I understanding this correctly .

    The CH water is just circulating through the coil of the buffer tank?

  • Moderators, Home & Garden Moderators Posts: 5,758 Mod ✭✭✭✭graememk

    No, The buffer tank water, is the heating water, and also the HP water. No coils.


    when the heating demand is low, you can see the tank stratifying

    If its freeezing outside, the HP will run its circulation pump to prevent freezing, this also will mix the tank

  • Moderators, Home & Garden Moderators Posts: 5,758 Mod ✭✭✭✭graememk

    Rad is coming off tomorrow for cleaning if I get a chance. Suspect it's blocked up

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  • Registered Users Posts: 2,414 ✭✭✭bullit_dodger

    I think that's sort of normal water flow/temp for a rad. Assuming that the water enters in the left side of that FLIR snap, it will rise up and travel along the top of the radiator and then back down out the exhaust. If it's cold and you open the valve, and have one hand at the top center and the other at the bottom, the bottom will take a long time (if ever) to completely get up to the top temp. Fan close to the entry/exhaust should boost though as you say.

    Also, have you considered a radiator reflector ?

    volila Radiator Reflector Foil - 5m x 0.6m x 4mm Folded Insulation Foil - Energy Saver Foil Insulation for Radiator Reflector Panels to Cut Your Winter Bills - Easy to Use Radiator Foil : DIY & Tools

    Would help cut down on heat absorbed by the wall, effectively that energy would go into the room instead.

  • Moderators, Home & Garden Moderators Posts: 5,758 Mod ✭✭✭✭graememk

    Wall wouldnt be taking that much heat. also radiators dont radiate, they heat by convection, There isnt much to reflect!

    Flow comes in from the right and exits to the left, I had both valves wide open for that photo and the radiator had been on for most of the day before that.

    This rad has been on for at least 15 years, and one of the first on its loop.

    It has been suspect for a good while, but with the stove, it hadnt been an issue until now.

    radiator off, onto the unregulated mains (plenty of pressure here) need to find my rubber mallet to try and dislodge everything and flushed out.

  • Moderators, Home & Garden Moderators Posts: 5,758 Mod ✭✭✭✭graememk

    Rad off, and flushed out a good bit of gunk, Some percussive maintenance with a rubber mallet too.

    Back on and heating. we shall see how it goes. (waiting for my buffer to heat up again)

    I am getting a line of hot across the bottom that wasnt there before but we shall see.

    Radiator is quite old and the first on the line so very likely has caught a lot of sludge over the years. we are now thinking 20+ years now. It predates the renovations in 2006-2008ish.

  • Registered Users Posts: 1,402 ✭✭✭DC999

    Fair play. I'd procrastinate for weeks, watch a million videos and then lose interest and never do it :)

  • Moderators, Home & Garden Moderators Posts: 5,758 Mod ✭✭✭✭graememk

    Well, Its been on my to-do list for the last year or so lol. Was always a bit suspect of it. With it struggling now it gave me the push needed to do it.

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  • Registered Users Posts: 6,622 ✭✭✭10-10-20

    That lower heat-line is the path of least resistance for the flow. That's why vertical (designer) radiators are commonly fitted with a flow diverter so that the main body of the radiator isn't bypassed.

  • Moderators, Home & Garden Moderators Posts: 5,758 Mod ✭✭✭✭graememk

    Yeah, especially in high flow systems. Seen that mentioned in a skill builder video

    It ain't a designer rad by any means 😂

    I still think it's under performing, I've got the bottom clear but I think there's still stuff stuck in the middle of the panel.

  • Registered Users Posts: 64,703 ✭✭✭✭unkel

    Always frown when people put the foil behind radiators. That measure has an infinite payback time (as it costs you money and the savings is zero)

    "percussive maintenance" 😁

  • Moderators, Home & Garden Moderators Posts: 5,758 Mod ✭✭✭✭graememk

    After another couple of days, the radiator was still struggling.

    I have upgraded the blocked 1400*500 double with an 1800*600 double.

    These are the outputs of a new radiator: (firefly compact, Double)

    I pulled the D50 stats and the conversion from this pdf

  • Registered Users Posts: 281 ✭✭JayBee66

    There's a recent Skill Builder/Heat Geek video where it is recommended that the home owner gets rid of his buffer and heats the radiators direct. I assume you use the buffer so that you can heat it from a variety of sources. However, the homeowner in the video has both heat pump and gas.

  • Registered Users Posts: 1,402 ✭✭✭DC999

    What is D50? Is that a delta of 50C from the heat at the top of the rad to the bottom? I assume it's that and not the temp of water in and out of the rad. I see the table in that pdf shows D50 as the benchmark of 1.00.

    But when YouTube installers talk about a D5 on a 35C flow rate to get a really good COP, does that D5 mean the difference between out and return temp back to the heat pump?

  • Registered Users Posts: 6,622 ✭✭✭10-10-20

    When talking about a rad, D50 should be DT50 (delta temperature 50) of the feed and return as measured at the radiator tails. When talking about a boiler then it's at the boiler tails.

    They are essentially the same for most intents.

  • Moderators, Home & Garden Moderators Posts: 5,758 Mod ✭✭✭✭graememk

    I thought D50 on a radiator is the difference between flow temperature and room temperature. Hotter room, Less heat that can be pushed into it.

    Suppose its much of the same.

    The radiator values in that document is at d50

    Heatpumps like a difference of 5c, but can handle more.

    This has implications for the flow rate through the system as

    power(kWh) = flow rate (L/s) x temp difference in c x 4.18(specific heat of water)

    So the smaller the difference in temperature the higher the flow rate needs to be to maintain a certain power.

    In my house, It comes in on 1", But drops to 3/4" at the T for the DHW, Then splits into a 3/4" T between the loop at the front and the back of the house.

    The flow is easily accessible, Return is behind the DHW tank. I can see it, and just about reach in and get at it, but not worth annoying it right now.

    Mines not the normal buffer though. instead of 50L, Its 500L and acts like a thermal store. I do gain a little bit of efficiency when the tank gets cold but drawback is responsiveness. I am toying with an idea of being able to do both, But would need to switch both flow and return. Enjoying tinkering with it and experimenting.

  • Registered Users Posts: 1,102 ✭✭✭manonboard

    This has been an excellent and very enjoyable thread OP. Thanks a lot.