Best storage heaters


Hi,
Wondered if anyone had any view on the best and most efficient make of electric storage heater? I was wondering about swapping the ones at my mother-in-law's which are great big things about a foot front to back and look like they date from the 50s or 60s.
TIA
Midge.
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in must equal heat out. However can you control it so that the heat comes out when it's required? Other than that it's simply a question of appearance and a modern one 'may' have better controls.
Peter
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wrote:

replaced with Dimplex models - chosen on best price to be found. Slimline, neat, beige and amazingly good heat out, compared to the old ones - which, it now turns out, weren't very good at all. I think they're all pretty much the same, heating elements, bricks and either fan assisted or not.
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Thanks for the replies guys.
We'd had a leaflet through for some german heaters (Wibo) but they sounded like they were going to be a bit pricey. Dimplex and Creda seem to pop up quite a bit for supply in the UK so we'll probably take a look at both and see whats best unless anyone else has any other strong recommendations.
Midge.

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Best & most efficient is "most are the same".
There are 2 key types of storage heater. a) Domestic - 13-14cm deep - 9-18-24kWhr capacity (35-70-105cm wide) - heat is released by convection via flap & "all over" - may have additional integral convective/fan heater
b) Industrial - 27-30cm deep - 24-32-40-48kWhr capacity (80-125cm wide) - fan outlet at bottom, lots more insulation - heat is released fan, little convection - remote thermostat controls fan operation
Type a) tend to have the same insulation. - Rockwool at the sides - Silica wrapped in glasscloth front - Silica slab top & bottom
Type b) tend to have similar, just more of it. - The idea is they lose less by convection - Heat is thus available on demand by thermostat - Their aim is office-hours plus boost for late workers
The benefit of storage heaters for commercial premises is they can sometimes get better rates on electricity AND they can eliminate all the maintenance & risk of water based systems. Typically good for shops, although air heat pumps are taking over (cooling in summer can be desireable) and will probably take over fully once reasonably priced CO2 based air heat pumps are available.
The bigger industrial units are Dimplex VFMi & Creda TSR. They are pricey - a bit too pricey because they are a single point of failure - although there is precious little in the things to ever fail. That is their attraction to many pensioners, they just work for 25yrs+. They are also branded AEG, Miele and so on in Europe. Forget importing now though re exchange rate, the Germans have quite a range though - about 6-7 industrial types of various functions.
The domestic units are Creda, Dimplex, Sunhouse, a few others. You have automatic & manual versions - automatic adjust their charge based on room temperature, so can save about 10% since you do not fully have to guess the next days weather (the real problem with pure storage heaters!). The manual versions require you to guess the weather - and then if it suddenly goes hot you are going to get a bit cooked.
There is a hybrid, the most popular is Duoheat. Duoheat come in 3 sizes - the largest is 2.5kW not the more usual 3.3kW, instead it uses a panel heater to provide boost heating after about 12-midday through to midnight-or-2am (there is a jumper inside re "disable 2hrs extra during charge"). The panel heater is small, about 0.39kW on the large 2.5kW (Duo500 unit and 0.29kW or so on the smallest unit (Duo300). The controller is electronic, you set the background (E7 overnight) charge, and you manually set the day boost (peak). This avoids the "cold in evening" or "sized to keep heat in evening but fry you overnight" - ie, it aims to fix the problem of insufficient insulation (basically) since their temperature is limited to about 920-980oC).
Duoheat should be very good. I did look at them some time ago for a relative, and will probably go for them "someday". Water based would not be ideal, she is a retired pensioner, and they provide a foolproof solution. I did enquire about parts prices, they are sensible re control-panel on top cost (about 12), internal PCB (29) and internal thin-film element panel heater (about 50). One issue is that they are electronic and thus might not be as reliable as the "capillary tube automatic type" such as the Creda TSR24AW (A = Automatic, 24 = 24kWhr charge or 7hrs * 3.3kW). So if I did go for them I may also buy a few select spares (do not want to bin a heater because a part failed.
Creda's Credanet is similar, but appears more ugly - Duoheat seems more popular.
Now, the fundamental problem is *insulation*. Storage Heaters work fine for pensioners with lots of insulation - roof insulation to 200-250mm, cavity wall insulation. Without those you are losing the bulk of the charge overnight and going to end up buying lots of heaters to compensate and paying a lot more. With cavity wall insulation, they should work *very well*. The reason is the insulation by virtue of being in the cavity uses the inner block/ brick as a thermal store, so the storage heater's night-charge limitations are then masked by the *thermal mass* of your wall. That evens out the up/down UK winter weather (9oC overnight one night, next night may be -3oC with a howling wind which for most houses strips heat out of them).
Storage heaters are thus a good "part of house or background heat" for a wood-burner / gas fires (not decorative which put more heat up the chimney than they give out and so suck the heat out of a house in doing so). They are good for pensioners, they are not good for people coming home at 7pm expecting the house to be warm :-) That would require careful sizing AND really good levels of insulation (1995+ if not 2007+ noddy house :-)
Very old storage heaters suffered 2 problems: - They had VERY poor insulation so lost a lot of heat overnight, running cold quickly the next day - Potentially asbestos content, which can be an issue
I think the old ones were limited to 480-520oC core temperature which is pretty hopeless. Modern units from 920-980oC which is a huge difference re temperature delta over ambient air through them as the thing depletes. They were a dead duck from the get-go, relying on gargantuan size and miserable insulation to basically warm your bum.
Alternatives? - Now, staywarm or warmup (can't remember the name) do grant assisted GCH installs. If your house is solid floors, complex joist layout, complex rooms re alcoves, doors, chimneys, multiple floors, unusual construction the result may not be pretty - and the misery is the grant is not "choose a local installer" which in my view is a key problem. They can install storage heaters in place of GCH, which can save a fair big lump of money - the biggest domestic storage heaters are 3.3kW and 350-400 each, if you need 2 big, 1 mid, 1 small, that is a lot of money. The electricity supply needs to be able to handle it - generally a 60A supply is limited to 2 big and 1 small , although it may be possible to upgrade it. Other alternatives are gas wall heaters, about 200-450 to buy and "whatever" to install. The UK products are a bit crap, a good one is Rinai 308 which is a 3kW output, microprocessor controller intelligent timer-controlled unit. It is Japanese and should be pretty reliable. They are not well known, but are a lot better than the dumb UK systems (Baxi, Drugasar, etc). They could easily heat a hall, bedrooms, bathroom, toilet from a hall position - 75kW output on maximum. I know a few people who installed them as backups to GCH and one who installed it in place of GCH and it really does heat the house (it has a fan in it, so does get the heat circulating around effectively). Fuzzy logic control.
- In 10yrs I expect CO2 air-heatpumps to be as common as convectors, pretty much, and slowly supplementing then replacing gas central heating. At present we are stuck on older refridgerant technology which whilst cheap (200) does not work so well at -5oC, CO2 gives 1 CoP down to -25oC and 3:1 CoP at a UK 0oC which is 3kW out for 1kW electricity in.
If they ARE great big things dating pre 1984, you WOULD get a benefit from fitting modern units.
If a 3.3kW input I would look on Ebay for the Sunhouse 24kWhr model in Automatic form, do not buy Manual. There are generics too which in Automatic form will probably be the same - although a brand name may make spares easier. Once fitted they are disliked by installers because they are called Fit-n-F***off because no maintenance or repairs are needed, you can see the hatred amongst the Wet GCH systems which I've never liked (underfloor GCH is a different matter).
Insulation first, fix that - at least loft-insulation (payback 1yr), then CWI (payback 2yr). Then do a few sizing calculations, you may want to check wiring size and check uk.d-i-y.
Alternatively she may qualify for GCH - just have someone there when they install to avoid the idiot-screwups (and there have been a few, can't use the stairlift, atrocious installs, leaks, cables drilled through, the usual trade-professional making a d-i-yer look like einstein, that sort of thing - avoidable by someone Advising them). Moben & Dolphin are little better, so take heart all such installers :-)
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I should add, Sunhouse are made by Creda (just cream vs white) under the parent Applied Energy. I think the same applies to others - that is they are a different cosmetic wrapper over a standard part.
Domestic E7 units have two points of failure, 1) resistor element (5-9-14) 2) charge controller which can be capillary or simple PCB (19). Contrast with GCH where a boilet has a 5-10yr replacement depreciation (200-300/yr), plus powerflush unless you want to stuff the new boiler (250), plus annual maintenance (100-150/yr).
GCH of course provides what E7 can't - you have total control at all times.
If we had built nuclear stations in the 1990s instead of gas turbine power stations things could be a lot better. Instead we made a pigs ear of it. Nuclear could provide baseband E7 nighttime charge, idiot green a cheap top up through the day via smart metering. Gas reserves in the world are high - just not ours, which means we are vulnerable to the "last 10% costing 90% of the total price" as far as energy companies are concerned. Gas in particular is pegged to oil, that could result in some nasty surprises over the next 10yrs.
E7 is good for pensioners, but look at the alternatives carefully. The Rinnai 308 in place of a 3.3kW automatic storage heater in say a hallway of a semi is not a bad idea, it provides heat on demand with good efficiency - without the pipe-running & replacement cost of a boiler.
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On Tue, 13 Oct 2009 16:52:31 -0700 (PDT), js.b1 wrote:

Thank you for these 2 posts - very informative.
I've 2 old storage heaters (not new when 'acquired') and realised on the first day that most of the heat was coming out of the front and back. I let them cool for 24h, dismantled them, raided the loft for some insulation and rebuilt them. After that they held heat all day and opening the flap in the evening kept the rooms warm until bedtime.
If ever I use my oven again, that'll be stuffed with more insulation on all sides.
--
Peter.
The head of a pin will hold more angels if
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Interesting reading - many thanks!

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Well worth creating a spreadsheet to evaluate the costs.
#1 GCH if only as a baseline (even if no gas) - Install cost - Ongoing cost re boiler replacement 5/10yr, powerflush cost, annual maintenance
#2 Air Source Heat Pump to radiators - Install cost (1k for 9kW unit) - Ongoing cost re replacement 10yr, annual maintenance
#3 Air Source Heat Pump (individual type) - Install cost (cheap n cheerful 220 to pro-install 850) - Ongoing cost re replacement 10yr, by which point CO2 will be <500 and the world will suddenly change due to their huge CoP even at UK temperatures with electric control & simplicity
#4 Economy 7 via "mechanical" automatic heaters - Install cost (TSR24AW TSR18AW etc)
#5 Economy 7 via "mechanical" automatic heaters with on-peak panels - Install cost (TSR24AW TSR18AW etc plus Contour 100, Monterey etc) - Spares cost (4-zone controllers are 85 etc)
#6 Economy 7 via electronic peak-n-E7 heaters - Install cost (Duoheat, Credanet) - Spares cost (electronic risk, 25 PCB vs 350 heater)
Loft & Cavity insulation are critical. Double glazing actually less so if good curtains with either thermal or double conventional linings. Adding a roller blind can also help.
A door sausage is critical during day & overnight especially if you have a gas fire with E7, otherwise the now heated chimney draws cubic- metres of icy cold air in overnight.
Personally I would not like E7 for the main living room, unless it were a no-heat-except-on-demand Dimplex VFM or Creda TSR. They are expensive and very big (due to heat capacity). The living room really needs a radiant heat source, not just convective re "real fire". One reason the "flame effect fires" don't quite work is they lack the radiant source. Better with a radiant source and LCD TV with real fire playing on it.
On demand peak heating need not be expensive, a 500W heater run 2hrs every night for 100 days is about 13 extra on the electricity bill. Easy to use a push-to-boost runback timer plugged-in to the heater or separately in a 1G box (often used on immersions re 15/30/1hr or 30/1hr/2hr).
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Thanks for the advice. It's a 30s semi but has had double glazing fitted, and recently the loft insulated and walls cavity filled (the heat wastage over the years must have been huge!) so at least we have a reasonable starting position.
Midge.
Well worth creating a spreadsheet to evaluate the costs.
#1 GCH if only as a baseline (even if no gas) - Install cost - Ongoing cost re boiler replacement 5/10yr, powerflush cost, annual maintenance
#2 Air Source Heat Pump to radiators - Install cost (1k for 9kW unit) - Ongoing cost re replacement 10yr, annual maintenance
#3 Air Source Heat Pump (individual type) - Install cost (cheap n cheerful 220 to pro-install 850) - Ongoing cost re replacement 10yr, by which point CO2 will be <500 and the world will suddenly change due to their huge CoP even at UK temperatures with electric control & simplicity
#4 Economy 7 via "mechanical" automatic heaters - Install cost (TSR24AW TSR18AW etc)
#5 Economy 7 via "mechanical" automatic heaters with on-peak panels - Install cost (TSR24AW TSR18AW etc plus Contour 100, Monterey etc) - Spares cost (4-zone controllers are 85 etc)
#6 Economy 7 via electronic peak-n-E7 heaters - Install cost (Duoheat, Credanet) - Spares cost (electronic risk, 25 PCB vs 350 heater)
Loft & Cavity insulation are critical. Double glazing actually less so if good curtains with either thermal or double conventional linings. Adding a roller blind can also help.
A door sausage is critical during day & overnight especially if you have a gas fire with E7, otherwise the now heated chimney draws cubic- metres of icy cold air in overnight.
Personally I would not like E7 for the main living room, unless it were a no-heat-except-on-demand Dimplex VFM or Creda TSR. They are expensive and very big (due to heat capacity). The living room really needs a radiant heat source, not just convective re "real fire". One reason the "flame effect fires" don't quite work is they lack the radiant source. Better with a radiant source and LCD TV with real fire playing on it.
On demand peak heating need not be expensive, a 500W heater run 2hrs every night for 100 days is about 13 extra on the electricity bill. Easy to use a push-to-boost runback timer plugged-in to the heater or separately in a 1G box (often used on immersions re 15/30/1hr or 30/1hr/2hr).
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