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Replacing storage radiators with something which still uses Economy 7 but can be controlled remotely...

Unless anyone uses the great majority of their electricity on E7, the premium paid for day-time usage swamps any E7 savings. Been there etc.

Take a year's usage figures and work the costs out - not difficult at all.

Storage heaters, just by virtue of how they work, and limitations of size, can never be controllable in any reasonable sense. That is very simple physics/thermodynamics. You might be in with a chance if the heaters were lagged feet thick, but that isn't practical.

As for running radiators from a tank using E7 to heat it? Again, the maths is mind-numbingly simple - volume of tank multiplied by SHC of water, mutiplied by temperature difference will give you the kWhr that can be stored. The tank would have to be trully vast for any significant heat storage.
 
garyi said:
Dont know about nest by I have Hive, and each rad I put a smart valve on. So now each room is controled by the smart valve. I have not done the math, but I think our gas is down like 20% this year, but there will be all sorts of factors I am sure.

Surely if the apartment is hot, then the nest will tell the boiler not to kick in?
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See opening post. Storage rads! Initial plan was a well insulated high capacity electric boiler which could heat the water off-peak and circulate according to a schedule but with overrides.
 
Cesare said:
We're in the process of buying a flat which uses a weird system i've not seen before. It's got traditional water radiators, but these are fed from a storage tank which is heated on economy 7. Basically there's a hot water storage tank which feeds the hot water + radiators, but this is heated by electricity. I'm rather dubious how efficient this is, but we'll see.

Obviously a system like this would allow you to keep the hot water economy 7, and use the nest system to decide when to heat the flat using the radiators.

The other thing the flat has that I didn't know about is a dual tariff electricity meter, so rather than a separate economy 7 circuit that powers one element in the heating, as I understand it, all electricity use through the meter switches between the two tariffs depending on hours, which seems pretty sensible to me.
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Great stuff, thanks. As @Vinny has just posted, you’ll need to do the same calcs I’d need to do… or as you will be taking on one of my system options you can be my R&D scout!
 
A kWhr is 3600J (3.6 kilo-joules).

I hope that I have the decimal point in the right place, but a realistic but absolute maximum heat storage for water comes out to be something like 0.16kWhr per gallon. You can't use water very cool for radiator heating and you can't really use scalding-hot water either. I used a 35C difference, but even an unrealistic 70C difference obviously only doubles the heat held by the water. It is a total and complete non-runner in practical terms.

The past/present winter has been crazy mild, so heating bills should be low.
 
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TheFlash said:
See opening post. Storage rads! Initial plan was a well insulated high capacity electric boiler which could heat the water off-peak and circulate according to a schedule but with overrides.
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Ah damn I fell at the first hurdle.

May I introduce you to HomeAssistant?

You could reasonably have a smart thermometer in the room, or get home assistant to pull from nest, then have smart plugs for on/off on the heaters, however I feel I have found my own demise in that they arn't usually on plugs?
 
kensalriser said:
Let out the flat and use the income to stay wherever you want whenever you want.
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I do let friends (including several Fishies) stay there for a contribution but that’s a handful of times a year. It’s not and never will be a commercial let AirBnB style; that would mean ditching the hifi, etc and I have zero interest in becoming a for-profit landlord. Its primary purpose is as my personal base in my home (birth) town with access to the Lakes.
 
garyi said:
Ah damn I fell at the first hurdle.

May I introduce you to HomeAssistant?

You could reasonably have a smart thermometer in the room, or get home assistant to pull from nest, then have smart plugs for on/off on the heaters, however I feel I have found my own demise in that they arn't usually on plugs?
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I’m going to poke this later. Thanks! As I have a dual rate meter anyway, one of the options I’m talking to an electrician about is dumping the separate circuit and replacing the 4 hard-wired wall plugs with normal 3-pins, with the whole flat on the one circuit. I need such specialist input on the practicalities and on the billing implications of same if any.

Good shout!
 
TheFlash said:
Many of these require the phone/device with the control app on it to be on the same wifi network as the radiators!
These might not be such but as I said up front I’ve been round the houses on this and given up each time because I couldn’t find the right product.
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yes and having to use an app is not very good with a holiday let !! more complication . my normal phone doesnt even have an app facility and many older folks dont have smartphones
 
Cesare said:
We're in the process of buying a flat which uses a weird system i've not seen before. It's got traditional water radiators, but these are fed from a storage tank which is heated on economy 7. Basically there's a hot water storage tank which feeds the hot water + radiators, but this is heated by electricity. I'm rather dubious how efficient this is, but we'll see.

Obviously a system like this would allow you to keep the hot water economy 7, and use the nest system to decide when to heat the flat using the radiators.

The other thing the flat has that I didn't know about is a dual tariff electricity meter, so rather than a separate economy 7 circuit that powers one element in the heating, as I understand it, all electricity use through the meter switches between the two tariffs depending on hours, which seems pretty sensible to me.
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Sounds the same as one i stayed at in Deia, it didn't work very well and cooled down the shower water if you turned the heating on. 3kW for the whole apartment might have been adequate in summer but in the winter with the first snow they'd seen for 20 years it was useless; had to spend most of the day in bed to keep warm.☺️
 
hifinutt said:
yes and having to use an app is not very good with a holiday let !! more complication . my normal phone doesnt even have an app facility and many older folks dont have smartphones
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It’s really not a holiday let… though I know what you mean! Most folk who do stay there are fellow hifi enthusiasts and use a smartphone, but I wouldn’t exactly expect them to download an app to control the heating. Something like Nest has a controller on the wall as well as app control and this is ideally what I want to use (or similar if necessary).
 
Vinny said:
A kWhr is 3600J (3.6 kilo-joules).

I hope that I have the decimal point in the right place, but a realistic but absolute maximum heat storage for water comes out to be something like 0.16kWhr per gallon. You can't use water very cool for radiator heating and you can't really use scalding-hot water either. I used a 35C difference, but even an unrealistic 70C difference obviously only doubles the heat held by the water. It is a total and complete non-runner in practical terms.

The past/present winter has been crazy mild, so heating bills should be low.
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3.6MJ.

It s a big number - but not when heating water at 4200J/litre/C !

(which is why even 9.6kW electric showers seem have a weedy output... that's what - 4.5l/min at a 30degC temperature raise? Something like that)
 
I spent some time this year digging into the Dimplex Quantum range when it looked like I was going to be skewered on a bad E7 night rate.

A couple of things to bear in mind: to get the best rate you need to be with British Gas, and they will determine when to charge the radiators. If you need a full charge then it's on for the whole of the E7 period. If not, then BG will remotely turn them to charge in the quieter periods for the required time to get to full charge. You have no remote control as such.

It's also worth bearing in mind that just as BG can offer the really low "Quantum" E7 night rate as they can control usage, they could also take it way/raise the cost. But I guess other suppliers may start to offer a similar "Quantum" rate at some stage. I calculated the ROI to be around five years for the heaters I need. Then EDF came up with a much improved fixed tarriff which pushed the ROI out to 10 years, so I parked the project.
 
re- thermal stores, although this prob belongs more on the recent ASHP thread offtopic...

My current project will have thermal stores 'buffer vessels', becos ASHP source everything*; >>60 tonnes, of...

( * a thing that becomes very nuanced on large schemes - sometimes, the right answer is to use the ASHP 'farm' to supply pretty-low temp 'ambient water' 25-30degc in bulk - good enough for underfloor heating; also -/excellent/ COP of the heatpumps year-round esp at low external air temps ; and then, small secondary local heatpump(s) to bootstrap that, to what you atually want 'locally' on demand - say 42-45degC for shower & handwash. It's all far more efficient that way - for certain uses: better COP always, much less direct loss from conventional high-temp, DHW storage - and circulation.
 
Have you ever thought about investing in a Tesla Powerwall 2 to store the lower priced electricity and then use the nest to control the rads remotely?
 
Rug Doc said:
Have you ever thought about investing in a Tesla Powerwall 2 to store the lower priced electricity and then use the nest to control the rads remotely?
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Depends on the heating demand. A Powerwall 2 is 13.5kWh max before you factor in any reserve for power cuts, and that does not cover a lot of daytime heating in the winter.
 
..then the Dimplex solution suggested above looks reasonable, but - Big question - what is the duty cycle, the use -cases you'd like to cover,,:
  • What sort of level of heating , how often, how warm / when?
  • Incidental other use - such as holiday lets?
  • Anything else you want to achieve ..?
- have a think about those edge cases, too. The better you can define, the easier it will be to find a good / economical solution.
 
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