Which heating system?

Adrian_mole_2

Hello guys, I have been looking through this great forum for a couple of hours now and I decided post my first thread.

Just like a lot of people here I am trying to chose a heating system for an old house I have just moved into.

I am tempted either by a heat pump or a wood pellet boiler. I'd quite like the pump as you don't have to buy fuel for it, but from what I have read so far it might not be the best for old properties. Someone on this forum mentioned a high temperature one??

Any comments are greatly welcome.

Thanks

Adrian

Adrian_mole_2

Any opinions pls?

Cardew

Welcome to the forum.

Old houses usually have poor insulation and thus are not ideal for an ASHP; and they are very expensive.

Obviously gas if available is the best solution.

You don't say how big the house is, and are you out at work all day? You wouldn't want a wood pellet boiler if you were at work??

It may be that simple cheap electric panel heating is the best solution?

More details and people can help.

antrobus

Adrian_mole wrote: »

I am tempted either by a heat pump or a wood pellet boiler. I'd quite like the pump as you don't have to buy fuel for it ...

Yes you do, it runs on electricity.

OK you don't have to buy fuel for it, you might have your own hydro-electric power plant in the back garden, or some other reliable source of free electricity, but generally speaking the likes of E.On charge for electricity.

As I understand things, a heat pump is a way of turning 1kw of electricity into 3kw of heat. So if you have no mains gas, it is an alternative that might be more 'green' particularly if you have a source of green self-generated power available. However if you have mains gas, you might as well burn 3kw of gas to get 3kw of heat, rather than have someone else burn 3kw of gas in a power station to produce 1kw of electricity which your heat pump then turns back into 3kw of heat.

(Yes I know that's not very scientific, but I think that's the principle of the thing.)

Oog

Piggy backing on this thread...

I also have a big old uninsulated house to heat and am looking at mains gas, but the plumber has suggested a combi boiler which I always thought was unsuitable for a large house. I have one now which I really like - hot water on demand - but I expect my new house to be a bit more future proofed and be able to deal with multiple hot taps on at the same time.

I will be keeping fire places/stoves for the main room heating.

Any green advice?

Oog

Cardew

Oog wrote: »

Piggy backing on this thread...

I also have a big old uninsulated house to heat and am looking at mains gas, but the plumber has suggested a combi boiler which I always thought was unsuitable for a large house. I have one now which I really like - hot water on demand - but I expect my new house to be a bit more future proofed and be able to deal with multiple hot taps on at the same time.

I will be keeping fire places/stoves for the main room heating.

Any green advice?

Oog

The downside of a combi is the inability to supply plentiful hot water - especially in winter when the mains input can be 3C or so. As you say it will not deal with multiple hot taps.

IMO the savings using a combi over the system boiler with a hot water tank tend to be exagerated.

A well lagged hot water tank will lose approx 2kWh in 24 hours with the water @ 65C - so in practice less than 2kWh.

In any case that heat is not 'lost' as it heats the fabric of the house - which is why the tank is usually in an airing cupboard.

Depending on the siting of a combi i.e. downstairs, you can lose more heat in the long pipe run to the upstairs bathroom.

thenudeone

Agree with much of above.
Electricity is 3 x more expensive than gas per kWh, so even with a 3x uplift from the heat pump, 3kW of heat from a heat pump costs about the same as 3kW of heat from gas.

plus sides
-low carbon footprint
-less reliance on oil/gas (with prices probably rising faster than leccy??)

down sides
-will stop working at very low temperatures (-17C last winter, for example!)
-heat pumps can only heat to about 60C which is insufficient for standard radiators, so you will need oversized radiators and / or fan-assisted radiators to make use of it properly
-also, you will need an immersion heater or other source to ensure the water is regularly heated over 60C to avoid legionella bacteria forming
These can be overcome if used as a primary source to warm the water to be used as the input to another more traditional heater, but the you have to invest in, and maintain, two heaters and probably a second storage tank.
-possibly noisy

Some good reports available here: http://www.ethicalconsumer.org/BuyersGuides/Energy.aspx for £3 each (a very small price to pay in relation to your possible investment)

Ben84

Mains gas as an alternative to a heat pump isn't such a bad idea as many people believe. The heat pump itself, at least in the UK is going to be largely powered by gas being burnt at the power plant at the moment anyway. We have such a focus on gas in electric generation right now and that's unlikely to change soon.

Gas also, although the cleanest fossil fuel, is still regarded as non-renewable and polluting while the electric grid, despite heavy reliance on fossil fuels at the moment is seen as something that can improve with time. However renewable gas is possible too. There's a functional pilot plant in Didcot that turns sewage in to methane and pumps it in to the gas supply where it's being safely used for heating and cooking right now. It's entirely reasonable to expect that we're going to get more low carbon energy from both the electric supply and the gas supply in the future. Buying an electric appliance with the hope that electric becomes more sustainable in the future is no more or less reasonable than buying a gas appliance with the same hope.

So, this leads to the question of what's best. Personally, I would go for the gas appliance if possible. They're popular well understood systems that work well and have lower installation costs. They are also not weather dependant as deliver their rated kW as long as gas is supplied. The gas pipes are also much more efficient at distributing energy than the electric wires, leading to much more of the energy going in to the system turning up as heat in your house. Heat pumps may enjoy high efficiencies, but they are still attached to a distribution system that loses ~70% of the energy between the power plant and your house.

ziggyman99

Ben84 wrote: »

but they are still attached to a distribution system that loses ~70% of the energy between the power plant and your house.

I'm sorry your wrong. Distribution and transmission losses, depending on the source, are between 7.4 and 8.5% Overall thermal losses are around 69%.
Transmission losses on the gas network amount to 2.1% with overall efficiencies up to 90%.

zeupater

ziggyman99 wrote: »

I'm sorry your wrong. Distribution and transmission losses, depending on the source, are between 7.4 and 8.5% Overall thermal losses are around 69%.
Transmission losses on the gas network amount to 2.1% with overall efficiencies up to 90%.

Hi

Back of the envelope thinking ....

Converting this to usable heat ... an electric fire, although 100% efficient has lost 69% of the embedded energy in the generation fuel, so is 31% efficient in carbon terms. Expanding this to an ASHP averaging a COP of 2.2 gives an effective efficiency of 68% ...

In comparison, gas distribution efficiency at 98% and boiler efficiency at 90% gives an overall 88.2%, so let's give a little leeway for the boiler running below max efficiency and say 83% in carbon terms.

That gives the equivalent of 68% energy converted for an ASHP (COP2.2 EST Av :exclamati:question::think::silenced:) v 83% energy converted for a condensing gas boiler (at 85% Av.Eff) ..... If you were concerned about conserving limited energy resources which would be the choice for you ....

Anyway, I'm pretty sure that Ben84 was referring to generating and "distribution system that loses ~70% of the energy between the power plant and your house. " , in which case the difference between 69% and 70% is irrelevant ....

HTH
Z

Ben84

ziggyman99 wrote: »

I'm sorry your wrong. Distribution and transmission losses, depending on the source, are between 7.4 and 8.5% Overall thermal losses are around 69%.
Transmission losses on the gas network amount to 2.1% with overall efficiencies up to 90%.

Hi Ziggyman99, I've not been entirely clear as I was thinking and should have written 'potential energy' rather than just 'energy' in my post. I was focussing on roughly 70% of the potential energy in the coal/oil or whatever is burnt at the power plant getting lost somewhere between going in to the power plant as unburnt coal/oil and arriving as electrons at your house.

Electricity is wonderful stuff, but not very efficient.

I suppose electric that's made without using a steam cycle plant (a few examples like hydroelectric and solar are in use) can't be seen so negatively as the major losses are in the steam cycle, not the wiring between the plant and your house? Power plants that send their waste hot water somewhere useful like district heating networks are also much more efficient. It's not all bad, but at least here in the UK where CHP is exceptionally rare and most power plants are steam cycle plants burning fossil fuels, we have a lot of potential for improvements and some way to go before hooking up anything to them looks sustainable.