storage heaters/electric central heating or gas?

punamulta

Ulkoyksikkö model
MUZ-FD25VAH
Lämmitysteho heat (kW) 1,5-6,3
COP (W/W)
5,25
just for information above is the spec for the Nordic Mitsubishi heat pump, which works fine down to minus 15 deg c

pdf in english http://www.latcomfort.lv/files/IntroductionMSZ-FD_sep07.pdf

Cardew

punamulta wrote: »

Ulkoyksikkö model
MUZ-FD25VAH
Lämmitysteho heat (kW) 1,5-6,3
COP (W/W)
5,25
just for information above is the spec for the Nordic Mitsubishi heat pump, which works fine down to minus 15 deg c

pdf in english http://www.latcomfort.lv/files/IntroductionMSZ-FD_sep07.pdf

I think we might be at cross purposes here. I am not sure what you are suggesting.

The models obviously have a great spec.

Far better than the one I have in a warm climate abroad!!

However those models are designed to heat a single room, not CH a house unless several of them are built in during construction. Each needs a big box outside.

The model you quote has a maximum output of 6.3kW.

What a quick glance of the specifications doesn't show is a graph of output against outside temperature.

The COP* of 5.3 you quote it will of drop off as the temperature decreases and at the -15C they quote I suspect it will be about 1.5 at best - I read the theoretical point at which unity is reached is -18C.


I found this quote from an independant source:

The technologies are developing rapidly: COPs (coefficient of performance) have risen from COP=3 to COP=4 or even COP=5 over the last five years. Heat pumps are now becoming popular choices for home-heating as well as for cooling — especially in areas with less severe winters.
Those buying air-source heat pumps should look closely at its COP, the outside temperature range in which that COP is effective, the cost of installation, how much heat it can move, and how much noise it generates.
Air-source heat pumps do not work well when temperatures fall below around −5°C (23°F).
Ground-source heat pumps typically have higher COPs than air-coupled heat pumps,

Even your link for New Zealand states:

Mitsubishi Electric air conditioners (or heat pumps) are capable of transferring up to 4kW of heat into a space while only consuming 1kW of electrical energy. This makes them extremely energy efficient. The energy efficiency of a heat pump decreases as the temperature difference between inside and outside becomes greater, but it typically provides 3 or more times as much heat as a normal electric space heater would provide with the same amount of electricity input.

What would the figure be in UK I wonder?

What they are ideal for is, say, a conservatory; but not practical to convert a house to fit them.

* For those unfamiliar with this term, COP = Coefficient of Peformance is the ratio of output to input power.

punamulta

the unit I use heats an area of 80-100 sq meters, maybe the open plan nature of our house in Finland (at 62deg north), and the insulation enables me to heat the whole house, but for the coldest of winter days [ -15 down to -40 ], when i have to resort to lighting the wood stoves.

I can honestly say i didn't believe the pump would work even when i switched it on! I was still really sceptical for several weeks, but had to eventually concede it does work.

My point is that the COP of air source has reached that of ground source, so is it worth the cost of digging up the garden at present to get the same heat.

The UK relatively has a very mild winter climate, with winter temps rarely dipping into double minus figures, air pumps should be fine here. Ice energy's units for example are Swedish and will find far more heat in the UK outside air.

Even at a worst Cop figure of 1.5, isn't that 50% more than an electric element? At the temps on this island you could reasonably expect 100% upwards.
A lot of winter days here are above zero , air pumps are operating close to their theoretical best cops once you get over +5 deg c.

Cardew

punamulta wrote: »

the unit I use heats an area of 80-100 sq meters, maybe the open plan nature of our house in Finland (at 62deg north), and the insulation enables me to heat the whole house, but for the coldest of winter days [ -15 down to -40 ], when i have to resort to lighting the wood stoves.

I can honestly say i didn't believe the pump would work even when i switched it on! I was still really sceptical for several weeks, but had to eventually concede it does work.

My point is that the COP of air source has reached that of ground source, so is it worth the cost of digging up the garden at present to get the same heat.

The UK relatively has a very mild winter climate, with winter temps rarely dipping into double minus figures, air pumps should be fine here. Ice energy's units for example are Swedish and will find far more heat in the UK outside air.

Even at a worst Cop figure of 1.5, isn't that 50% more than an electric element? At the temps on this island you could reasonably expect 100% upwards.
A lot of winter days here are above zero , air pumps are operating close to their theoretical best cops once you get over +5 deg c.

I hope I haven't come across as anti heat pump.

I am sure that you are right that as prices come down, they will become more popular for new builds particularly for smaller houses.

At a COP of over 3 they start to compete with E7 storage heaters in running costs; but not in installation costs. It is a little disappointing that Mitsubishi only give a 3 year guarantee and there is a lot of high tech cutting edge technology that could go wrong. With Storage heater there is virtually nothing to go wrong(the current thread with a faulty thermostat is the first fault I have heard about.)

The advantage of Ground Source Heat Pumps is that they can be used in conjunction with a Thermal Store and thus use Economy 7/Economy10 at around 3p/kWh - a COP of 3 makes huge sense then.

samtheman1k

I think that I am going to go with the Mitsubishi ASHP combined with the Gledhill Boilermate that will act as a thermal store. As the alternative is electric heating (e.g. electramate or NS heaters), then I think that this will provide a good alternative.

See here: http://www.gledhill.net/water-storage/ws-index.htm under 'alternative energies'.

With E10, off peak electricity prices are 5p/kwh, and thus even with a COP of only 2, it will be the same price as gas, and will be cheaper than gas as it warms up...that's the theory at least! Even on peak time (8.7p/kwh, it will still be cheaper than oil probably and not a million miles away from gas prices, especially when you take no annual servicing into account.

However, the HP + TS will be about £4.5k + installation, but comparing that with the cost of installing gas (excavations, ROWs, etc etc), I think that it will be pretty much even in the medium term at least.

I'll let you know in a few months anyway!!!

samtheman1k

Cardew wrote: »

The advantage of Ground Source Heat Pumps is that they can be used in conjunction with a Thermal Store and thus use Economy 7/Economy10 at around 3p/kWh - a COP of 3 makes huge sense then.

But an ASHP on E10 with a thermal store would also make sense and have significantly less installation costs.

Cardew

samtheman1k wrote: »

But an ASHP on E10 with a thermal store would also make sense and have significantly less installation costs.

I don't understand what you are suggesting.

Perhaps I have missed something, but how do you 'convert' the warm air from an ASHP into heat for the thermal store?

Then how do you get the heat from the thermal store into your rooms?

samtheman1k

Cardew wrote: »

I don't understand what you are suggesting.

Perhaps I have missed something, but how do you 'convert' the warm air from an ASHP into heat for the thermal store?

Then how do you get the heat from the thermal store into your rooms?

By using an air-to-water heat pump that outputs warm water from the heat pump. This then goes into a thermal store to heat the store indirectly, and this store than then be connected to your wet radiator system.

punamulta

don't forget to shop around and haggle like mad, the players in the heat pump market here are still testing what the market will stand price wise, prices are already much lower elsewhere in europe.

Cardew

samtheman1k wrote: »

By using an air-to-water heat pump that outputs warm water from the heat pump. This then goes into a thermal store to heat the store indirectly, and this store than then be connected to your wet radiator system.

I hadn't appreciated you already had a wet radiator system installed.

I also wasn't aware that the Mitsubishi ASHP had the facility to connect its output to an air to water heat pump(a convertor) I would be interested in how this works(and how efficient it is) have you any technical details?

As you are no doubt aware, the Achillies heel of GSHPs is their inability to get water hot enough for conventional radiator systems - which is why underfloor heating is recommended.(or install bigger radiators)

What is the maximum temperature of water that your ASHP/converter will provide?