storage heaters/electric central heating or gas?

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?

peat

I use a thermal store system heated by an electric heater. I was advised that the water in the store should be maintained at around 80 degrees centigrade. Can a ASHP bring water to that temperature?

samtheman1k

peat wrote: »

I use a thermal store system heated by an electric heater. I was advised that the water in the store should be maintained at around 80 degrees centigrade. Can a ASHP bring water to that temperature?

No you can't; you'd have to boost it with electric to get to that temperature as the ASHP will only get to around 55deg (although the cost of doing this is going to be less than heating purely by electric). However, I believe that you only need to get to that temperature for two reasons...firstly, for destroying legionaires disease IIRC you need to heat it to above 60degC once a week, although i'm not sure how relevant this is for indirect systems where you don't actually come into contact with the water in the store.

Secondly, normal radiators are designed to be run at around 80degC, so if you created a system based on 55deg water, you would need to oversize the radiators. How much to oversize is the problem, with claims from 20% to 100% to provide the same level of comfort. Alternatively, you can use underfloor heating that is designed to operate at around 35deg (which is the preferred solution).

The system I'm looking at is the Gledhill Boilermate HP-DEM combined with a Mitsubishi heat pump (sold as a package direct from Gledhill). The HP is as follows:

http://www.mitsubishi-aircon.co.uk/default.asp?url=http://www.mitsubishi-aircon.co.uk/mitsubishi_electric.asp?id=168143

and the Boilermate is on the Gledhill.net website under alternative energies:
http://www.gledhill.net/water-storage/ws-index.htm