Someone "in another place" was asking about electric combi boilers
I have no experience of such beasts, does anyone have any positive recommendations ?
... and no, he's not interested in alternative recommendations, just what to go for in an electric combi
I wouldn't fancy one. My gas combi, which gives adequate but not outstanding performance, is rated at 27kw. At 230v that's 117 amps. Please ensure he doesn't run it off a spur from the ring main via a three-way multi socket.
Cheers!
Martin
I wouldn't fancy one. My gas combi, which gives adequate but not outstanding performance, is rated at 27kw. At 230v that's 117 amps. Please ensure he doesn't run it off a spur from the ring main via a three-way multi socket.
Cheers!
Martin
service supply of =E2=89=A5 100A per phase.
- The 12 KW boiler must be installed in premises having a system impedance of not more than 0.1939 + J 0.1939=E2=84=A6"
Anyway, they aren't combi boilers. They have a considerable amount of stored heat. "Design to operate on peak avoidance tariffs" means they can't operate instantaneously.
Owain
It's a thermal store. It will fill it fast and instantly heat the incoming cold water.
If mains gas is available in the street, oddly enough, use that :-)
Taking 15,000kW total heating cost for heating.
E7 cost...
- Energy =3D 5p / unit
- Maintenance =3D zero
- Depreciation =3D =A3100/yr or 10000/15000kW =3D 0.7p / unit
- Effective Cost =3D 5.7p / unit
Gas cost...
- Energy =3D 5p / unit
- Maintenance =3D =A3100/yr or 10000p/15000kW =3D 0.7p / unit
- Depreciation =3D =A3300/yr or 30000p/15000kW =3D 2.1p / unit
- Effective Cost =3D 7.8p / unit
Depreciation is the 10yr replacement of boiler, powerflush, odd radiator, TRV, improved programmer and such odds n sods.
Notes :-)
1 - If the heating is 30,000kW per year figures change. 2 - If you need peak elec boost, cost is 2.5x HIGHER.For electric boilers... #1 Insulation must be very high a) recent house b) Cavity & Loft insulation and chimney's trickle vented.
#2 Thermal store is required The bigger the better to best use cheap rate electricity, with
75-100mm rockwool insulation "sock" rather than the miserable 25-50mm expanding-foam-in-place stuff.#3 Electricity rate must be E7 or E10 E7 requires a gargantuan thermal store, E10 can reduce it a little.
#4 You hit the limits of the supply cable.
7hrs at 9kW =3D 63kWhr... that is not actually a lot. 10hrs at 12kW =3D 120kWhr... that is pretty reasonable.Realise the volume of thermal store you need after the house is initially heated overnight, it's really enormous - 1000L or 1500L. The figures do not work well, you end up needing peak or E10 because you just don't have a liquid sodium thermal store handy at B&Q.
Hence they are favoured for well insulated flats, anything else gets tough - you need 3-phase E7.
The solution would be a 9kW heat-pump (=A31k), plus thermal store, plus backup E7 "brick" storage heaters for the coldest days. That will become quite a common solution in about 10yrs, CO2 heat pumps whilst nutty price now (3.7k vs 1k) will eventually drop in price, it is just a dual-stage DC compressor - hardly rocket science just lack of economy of scale and screw the early adopters as usual.
As to actual install - make sure the terminals are tight, because quite a few burn-out the PCBs if they are not.
Some idiot-installs have a) not used a thermal store b) not used a suitable E7 E10 rate - in either case the result is horrific as you can imagine.
Roger Mills wibbled on Wednesday 21 October 2009 14:38
It's like a gas combi, only more crap ;->
Though, I would like a bit of background violin accompaniment now... Until my heating system is done (ha) I will be living off a 9kW multipoint heater[1]. Time to fill bath about 20-30 minutes...
[1] Because it's cheap (to buy), simple quick bodge and I can recoup some of the capital on ebay later...Correction...
#4 You hit the limits of the supply cable.
7hrs at 9kW = 63kW... that is not actually a lot. 10hrs at 12kW = 120kW... that is pretty reasonable.On the face of it, it seems fine.
The reality is the problem of thermal store sizing. Which translates into using on-peak, economics go AWOL.
If it is for a 1-bed flat, they will work fine. For anything bigger, you balance heat store size/number against on- peak electricity usage.
In message , geoff writes
Well, thanks for the contributio0ns, but nobody actually answered the question, did they
maybe an omen for him
Probably because true electric instant water heating is simply not viable for domestic customers because of the limitations of supply.
If we all had individual micro-reactors at home then it could be a very interesting possibility.
Owain
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