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DIMPLEX Storage Heaters & THTC tariff


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Long standing gripe of mine and still not found the answer.

Our dimplex heaters (and hot water) are the hostages to the Hydro and when they want to send power to them. Surely if they are at capacity of stored heat the heater should "refuse" any additional power input that the hydro deem needed to be supplied.

Power is fed to them at weird times and I'm never convinced its always needed. I've taken now to only having the water heater on between 05.45 and 07.00 and turning it off to stop it taking in power. To do similar with the dimplex heaters may be counter productive but surely there must be a way to better control the intake. A latest bill of £811 has me considering having meters changed, heater efficiency checked and changing providers.

But first, I want to understand the supply of power and how I can manage it without allowing the hydro a license to determine how much my bill will be.

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The Dimplex storage heaters I'm familiar with have all had two controls. an input and output. The more you turn the input down the less heat will be stored in the heater and the less power it uses. The trick is figuring out how low you can set the input control and be almost run out,  but not quite of stored heat before the timer kicks in next to recharge it back up. Not an easy task given that you've got to second guess how much heat you're gonna need 12-24 hours in to the future.

Its a fine enough idea in a very modern house with tip top insulation and draught proofing as indoor temps don't get influenced all that much all that quickly, different story even with some houses no more than 20 years old where a change in wind strength or direction can turn the place from a sweat box to an ice box in a couple of hours. Without spare stored heat to call upon to compensate at such times you either sit and freeze a while or have to pull in temporary conventional heating, which cancels out the small savings for storage heating usage worryingly quickly.

A new or near new high spec house, or in town or a few really sheltered locations its probably fine and well, but anywhere else in Shetland its very difficult not to end up paying for heat you don't use and still and on ending up with a few hours here and there that you need to keep your jacket on, and thats with watching the weather forecast and attempting to fine tune the input/output settings daily to best cope with the predicted weather.

A leaflet came through the door the other week bragging that 'there was now an alternative supplier to SSE for THTC customers. I've not got round to reading it yet, but if its not been chucked already, I'll see if I can dig it out and see if its promising anything worthwhile/realistic.


Edited by Ghostrider
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Cheers Ghostrider.

You've summed up neatly the frustration I have for something that a thermostatic control could easily deal with.

As you say, predicting what the temperature will be is one issue, the other is predicting when the hydro will decide when they think we will need more power without knowing how much heat we have stored. Its a license for them to affect our bills outwith our control. Its a mockery of total heat TOTAL CONTROL.

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I had THTC storage heaters, and realised they were giving me boosts when I didn't need it. Probably when their other demand was low. And still they were getting cold by 9 o'clock. Also working out the number of units used , found it would have been cheaper on a single rate from a cheaper supplier such as bulb or octopus. I also changed my heating to air to air, and for a while it has saved me up to £100 a month. I never use their estimated readings.

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  • 2 weeks later...

@RugyDavy, the limitations you're describing are more the result of design of the 'old style' storage heaters and water tanks rather than supply times / tariffs. 

I've fitted many of them over the years, and they're inherently basic in principle and limited in terms of controllability - they convert electricity via a heating element into heat stored in either water or clay bricks - but it takes guesswork (and weather forecasting) to figure out where to set the storage heater input controls and water heater thermostats to ensure you'll have the right amount of stored heat and hot water for the next day or so. You shouldn't need to switch the storage heaters or water tank supply off - the storage heater input control and water tank thermostat will control how much power is converted to stored heat.

Once the heat has 'gone in', the old style storage heaters are particularly difficult (impossible?) to control as they work on the principle that heat seeps out all day, like a poorly insulated leaky 'bucket of heat' that the Hydro tops up when the power supply comes on. And because the leak is pretty much constant (the 'output' control just operates a peerie mechanical hatch above the clay bricks to let a little bit more heat out, but they're pretty ineffectual), the heaters will heat your house all day and all night regardless, unless they run out of heat before the Hydro supply kicks in again. I don't think that design of heater is even manufactured or sold in the UK anymore.

However, modern "High heat retention" storage heaters are considerably more efficient and controllable. They still work on the principle of heat stored in bricks, but the insulation is much better (the outside of the heaters is generally cool to touch) and heat is emitted with the aid of a fan controlled by a timer and thermostat. Modern heaters are often 'smart' and can predict how much energy to take on board based on previous and future program settings. So they're still like 'buckets of heat', but with a tightly fitting lid and controllable taps instead of just a leak!

The Dimplex Quantumn high heat retention storage heaters are common in Shetland as Hjatland and the SIC have installed hundreds in their properties. Dimplex actually trialled them in Shetland a few years back before making them commercially available.

After much research and discussion, I've not long ago replaced the old beige Dimplex storage heaters in my house with Quantum heaters and I've been very impressed thus far, although the fan noise was a little distracting to start with and it took a while to get the temperature and timer settings right. I was a little sceptical about how controllable storage heaters could be, but the Quantum heaters really are different beasts to the old style storage heaters.

They're not cheap to buy, but there are interest free loans available which would help balance the long term savings in heating efficiency against the upfront costs of installing them - https://www.homeenergyscotland.org/find-funding-grants-and-loans/interest-free-loans/


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  • 1 year later...

I'm hoping someone can help advise on the electricity tariff for Quantum storage heaters. Currently have 2 meters which give 3 readings one is economy 7 with 3 readings and the Quantum storage heaters is on the other meter which I believe is split into blocks throughout the day of off peak power which gives the charge to the heaters.

As I understand it the Quantum heater works out how much charge to take for the following day just before midnight.

So my question is do Quantum storage heaters require the second meter with the off peak blocks split throughout the day, or could they operate just as well on Economy 7?


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