Heat pumps

[bigroomboy]

There seems to be a general misconception through these posts that heat pumps only work in super insulated homes. The amount of insulation is irrelevant other than total heating demand. In a good heat pump install where it is cheaper to run that alternative fuels then you would actually save more by going for a heat pump. The first thing that needs to happen is the government removing the carbon intensive fuel tax added to electricity as it is now actually the cleanest energy source on average. That would make it a no brainer but already well installed systems are achieving SCOP values over 400% which makes them far cheaper to run than gas. Proper design and installation is essential as if it's not running effectively then you won't get enough heat and that scop can quickly drop to 2.5 and cost a lot more than gas. Looking at government data the average SCOP from their survey was 2.8 - dreadful and accounts for all the bad press about heat pumps. With the electricity tax in place you need SCOP of 3-3.5 to break even with other fuels.

[JohnfromUK]

16 minutes ago, bigroomboy said:

The amount of insulation is irrelevant other than total heating demand.

Technically true, but owing to the way many people use their heating, it is not the whole story.

Most people in the UK use a 'programmer' to only have the heating on when the house is occupied - which for many people is early morning and late afternoon/evening, and many are turned off overnight.  This works with a UK traditional heating system where high water flow temperatures give a fast response.  It also means that because the house is cool much of the time, heat loss (which depends on the temperature difference between inside and outside) through poor insulation is lower.

The 'on when occupied' principle works less well with a heat pump, which has a relatively low flow temperature and so a longer 'warm up' time for the property.  They are best suited to running for long periods, or even continuously.  IF you are heating a house continually 24/7 high grade insulation performance is much more important, or your losses will be high because with the house continually warm, losses through walls, roofs, windows, air exchange are high for the whole time.

I don't know how to measure the SCOP, but I read that at an outside air temperature of 0 Centigrade, 2.5 is not uncommon for air sourced.  Ground sourced/water sources are better, and air sourced are better at higher outside air temperatures.

It is true that the underlying problem in the UK is really poorly insulated housing - but it is NOT easy to put that right in existing older buildings.  Various things like 'spray foam' insulation that people try can have catastrophic side effects.  Many older UK properties require significant ventilation to prevent damp.

I have exhausted a lot of time and not insignificant funds on insulating my (older and listed) property, but there is only so much that can be done within the limitations of 200-300 year old main walls and rules on 'allowable' works that can be carried out.

 

[udderlyoffroad]

1 hour ago, bigroomboy said:

Proper design and installation is essential as if it's not running effectively then you won't get enough heat and that scop can quickly drop to 2.5 and cost a lot more than gas.

This. - The government attempting to sell them as 'drop in' replacements for gas boilers is just idiotic.  The media, seemingly unable to move beyond questioning why they're not drop ins, isn't much better.

 

1 hour ago, bigroomboy said:

Looking at government data the average SCOP from their survey was 2.8 - dreadful and accounts for all the bad press about heat pumps.

Jebus, had no idea it was that bad.

1 hour ago, bigroomboy said:

With the electricity tax in place you need SCOP of 3-3.5 to break even with other fuels.

Trouble is, Rishi has just remembered he needs to at least pretend to want to win the next election, moving the green levy from electricity to gas would be electoral suicide.  Abolishing it altogether would be better*

*Yes, given I'm a recipient of the ECO4 grant, funded by the green levy, I'm aware of the I'm-alright-Jack-ery of this - Still think letting people keep their money is better overall.

[Yellow Bear]

Another thing that cripples heat pump performance is that when twinned with UFH is people will insist on "lagging" floors with wall to wall carpet.   Tile or even terrazzo is best.

[discobob]

I have heard figures about how much of our energy in our home is supplied by "green power". This is only the electric portion which only accounts to 20% of a homes energy footprint I believe (could be wrong) with the remainder coming from gas/oil.

so when 50% of a home energy is supplied by green - that is actually only 10% of the homes energy requirements. So if we all switched to using electric that would mean we would have to increase our electricity supply tremendously.... and the sun doesn't always shine, and the wind doesn't blow - and besides - they are an ecology disaster waiting to happen....

[bigroomboy]

3 hours ago, discobob said:

I have heard figures about how much of our energy in our home is supplied by "green power". This is only the electric portion which only accounts to 20% of a homes energy footprint I believe (could be wrong) with the remainder coming from gas/oil.

so when 50% of a home energy is supplied by green - that is actually only 10% of the homes energy requirements. So if we all switched to using electric that would mean we would have to increase our electricity supply tremendously.... and the sun doesn't always shine, and the wind doesn't blow - and besides - they are an ecology disaster waiting to happen....

It's closer to 40% no or low carbon (wind, solar, nuclear, hydro, biomasses) and improving rapidly. You do have to take account of electrical transmission loses around 7-10 % though.

We can actually generate more but at times it's limited by the ability to transport, hance all the pylon upgrades at the moment.

[12gauge82]

10 hours ago, JohnfromUK said:

Technically true, but owing to the way many people use their heating, it is not the whole story.

Most people in the UK use a 'programmer' to only have the heating on when the house is occupied - which for many people is early morning and late afternoon/evening, and many are turned off overnight.  This works with a UK traditional heating system where high water flow temperatures give a fast response.  It also means that because the house is cool much of the time, heat loss (which depends on the temperature difference between inside and outside) through poor insulation is lower.

The 'on when occupied' principle works less well with a heat pump, which has a relatively low flow temperature and so a longer 'warm up' time for the property.  They are best suited to running for long periods, or even continuously.  IF you are heating a house continually 24/7 high grade insulation performance is much more important, or your losses will be high because with the house continually warm, losses through walls, roofs, windows, air exchange are high for the whole time.

I don't know how to measure the SCOP, but I read that at an outside air temperature of 0 Centigrade, 2.5 is not uncommon for air sourced.  Ground sourced/water sources are better, and air sourced are better at higher outside air temperatures.

It is true that the underlying problem in the UK is really poorly insulated housing - but it is NOT easy to put that right in existing older buildings.  Various things like 'spray foam' insulation that people try can have catastrophic side effects.  Many older UK properties require significant ventilation to prevent damp.

I have exhausted a lot of time and not insignificant funds on insulating my (older and listed) property, but there is only so much that can be done within the limitations of 200-300 year old main walls and rules on 'allowable' works that can be carried out.

 

This is correct.

A property connected to mains gas is always going to be hard to beat using a heat pump, particularly if it is poorly insulated where the flow temperature of the water it can produce without direct eletric heating is much lower.

Also, A very poorly insulated property is going to struggle to make temperature using a heat pump and even oversize radiators vs gas fired central heating.

[bigroomboy]

8 hours ago, 12gauge82 said:

This is correct.

A property connected to mains gas is always going to be hard to beat using a heat pump, particularly if it is poorly insulated where the flow temperature of the water it can produce without direct eletric heating is much lower.

Also, A very poorly insulated property is going to struggle to make temperature using a heat pump and even oversize radiators vs gas fired central heating.

Not really. As I pointed out above. A well installed system can already make you significant savings in money and carbon impact. The problem is that many systems are not well installed. Add to that potential increases in gas prices and possible removal of the electricity carbon tax and it could swing dramatically. It's also likely heat pumps will offer better operating efficiency in the future.

[12gauge82]

1 hour ago, bigroomboy said:

Not really. As I pointed out above. A well installed system can already make you significant savings in money and carbon impact. The problem is that many systems are not well installed. Add to that potential increases in gas prices and possible removal of the electricity carbon tax and it could swing dramatically. It's also likely heat pumps will offer better operating efficiency in the future.

Yes really 😂.

Without a well insulated home running with radiators, your either going to have a system that can't make temperature when cold outside or have to run such a large heatpump the rest of the year it is going to be very inefficient to run, with the eye watering cost implications that go with it.

Yes you could in theory put a heatpump on just about any property, is it practical and cost effective for poorly insulated houses, answer no.

[JohnfromUK]

In fact the 'bottom line' on this is as follows;

1. Well insulated houses are relatively easy to heat - and much more economical compared to poorly insulated houses.  This applies whatever the energy source used as a well insulated property simply looses less heat to it's outside surroundings.
2. Poorly insulated properties are much more demanding, both on needing more energy (as more heat is lost to it's outside surroundings) but also because it is likely a more complex system may be specified to control heat better (mine for example in an old, listed and hard to insulate property) has four zones.
3. At present, you cannot escape the high price differential between different raw energy sources (gas, oil, wood, electricity etc.), and the high cost of some types of boiler/heatpump/associated mechanisms and installations such as thermal stores, ground heat gathering, flues needed etc.

[udderlyoffroad]

21 minutes ago, 12gauge82 said:

or have to run such a large heatpump the rest of the year it is going to be very inefficient to run

To a certain extent of course, all heat pumps are grossly oversized for summer duties - I.e. making DHW.  Mine runs for about 5-10mins a day after we've all showered to top up the tank.

But i'm not sure that's particularly an issue anyway.  It is, after all thermostatically controlled, and modern heat pumps feature inverters to control the compressor.  When the tank is to temperature, it turns off.

Of course, the proper solution to this is a PV solar and a diverter to turn the excess electricity generated into hot water.  Not via the heat pump but via the immersion coil.  That way the heat pump need not run at all in summer months (of course that brings its own issues, but hardly difficult to manage)

[12gauge82]

2 hours ago, udderlyoffroad said:

To a certain extent of course, all heat pumps are grossly oversized for summer duties - I.e. making DHW.  Mine runs for about 5-10mins a day after we've all showered to top up the tank.

But i'm not sure that's particularly an issue anyway.  It is, after all thermostatically controlled, and modern heat pumps feature inverters to control the compressor.  When the tank is to temperature, it turns off.

Of course, the proper solution to this is a PV solar and a diverter to turn the excess electricity generated into hot water.  Not via the heat pump but via the immersion coil.  That way the heat pump need not run at all in summer months (of course that brings its own issues, but hardly difficult to manage)

It would actually be better particularly in summer months to use a heat pump to make hot water rather than an immersion as electricity converted directly to hot water via an immersion is nearly 100% efficient, but heating water via a well set up air source heat pump could be up to 200-300% efficient as its using the heat avaliable in the air and only extracting that potential using electricity via a compressor and heat exchanger.

Using a larger heatpump to attain a given temperature is always going to be less efficient than a smaller one, if decent insulation levels are used.

[Scully]

Wrong thread! 🙄

Its been a hard week! 

Edited September 26, 2023 by Scully

[udderlyoffroad]

36 minutes ago, 12gauge82 said:

It would actually be better particularly in summer months to use a heat pump to make hot water rather than an immersion as electricity converted directly to hot water via an immersion is nearly 100% efficient, but heating water via a well set up air source heat pump could be up to 200-300% efficient as its using the heat avaliable in the air and only extracting that potential using electricity via a compressor and heat exchanger.

One of those cases of yes buuut....my solar installation is 4 kW due to the size of my roof and the limit of 12 panels available on the grant, my heat pump is 12 kW.  Whereas the back up immersion coil is 3 kW.  Some diverters on the market effectively current limit immersion coils to power available (in steps) too.

Of course it would be better if the excess solar could run the ASHP, but the installation starts to get complicated.  As the energy is effectively 'free', you care less about efficiency.

This is one of those situations that will improve as suppliers start to develop ASHPs more suited to the UK market.

50 minutes ago, Scully said:

Wrong thread! 🙄

Its been a hard week! 

Don't worry, according to the energy bill, rules of engagement means the police will check you have a gas boiler before they open fire.

I'll get me coat.

[12gauge82]

32 minutes ago, udderlyoffroad said:

One of those cases of yes buuut....my solar installation is 4 kW due to the size of my roof and the limit of 12 panels available on the grant, my heat pump is 12 kW.  Whereas the back up immersion coil is 3 kW.  Some diverters on the market effectively current limit immersion coils to power available (in steps) too.

Of course it would be better if the excess solar could run the ASHP, but the installation starts to get complicated.  As the energy is effectively 'free', you care less about efficiency.

This is one of those situations that will improve as suppliers start to develop ASHPs more suited to the UK market.

Don't worry, according to the energy bill, rules of engagement means the police will check you have a gas boiler before they open fire.

I'll get me coat.

Makes sense 👍

[Scully]

58 minutes ago, udderlyoffroad said:

 

Don't worry, according to the energy bill, rules of engagement means the police will check you have a gas boiler before they open fire.

I'll get me coat.

😄 That’s a relief! 

[bigroomboy]

6 hours ago, JohnfromUK said:

In fact the 'bottom line' on this is as follows;

1. Well insulated houses are relatively easy to heat - and much more economical compared to poorly insulated houses.  This applies whatever the energy source used as a well insulated property simply looses less heat to it's outside surroundings.
2. Poorly insulated properties are much more demanding, both on needing more energy (as more heat is lost to it's outside surroundings) but also because it is likely a more complex system may be specified to control heat better (mine for example in an old, listed and hard to insulate property) has four zones.
3. At present, you cannot escape the high price differential between different raw energy sources (gas, oil, wood, electricity etc.), and the high cost of some types of boiler/heatpump/associated mechanisms and installations such as thermal stores, ground heat gathering, flues needed etc.

Good summary

[Humblepie]

On 25/09/2023 at 10:37, old man said:

Net zero, another introduction to modern slavery?

Can only be slavery if you comply 

[old man]

10 minutes ago, Humblepie said:

Can only be slavery if you comply 

You will have no option, slowly, situations are created that increase state control and fashion society towards a compliant mass without any rights that ensure any personal control of their future?

[Humblepie]

39 minutes ago, old man said:

You will have no option, slowly, situations are created that increase state control and fashion society towards a compliant mass without any rights that ensure any personal control of their future?

As stated, only if society complies and allows it to happen

[old man]

13 hours ago, Humblepie said:

As stated, only if society complies and allows it to happen

Maybe,  we have on reflection reached the stage where there is no chance now to comply already? Politicos ploughing their own agenda irrespective of any electoral promises? Two opposing mobs safe in the knowledge that whatever happens they are insulated and unassailable? Neither will vote for anything that compromises their 5 star heaven?

We are where we are? 

[12gauge82]

47 minutes ago, old man said:

Maybe,  we have on reflection reached the stage where there is no chance now to comply already? Politicos ploughing their own agenda irrespective of any electoral promises? Two opposing mobs safe in the knowledge that whatever happens they are insulated and unassailable? Neither will vote for anything that compromises their 5 star heaven?

We are where we are? 

Absolutely true

[Bigbob]

We have insulation between the beams on the floor of the loft then its floored its rather nice painted green and got fields ect on it , its where  the previous owner played with his trains , Then i put fibreglass insulation between the roof beams and held it up stapling garden fleece over the top . My mates often said its warm in here you got the heating on ?. Then we only run the heating from mid October to March . The gas board are saying as the boilers nearly 20 years old its needing replaced its getting serviced on friday so we will see but if they still have trouble accessing parts i still think another boiler will cover my needs i know a farmer who has a heat pump and moans about it but its a big old farm house 

[JohnfromUK]

5 minutes ago, Bigbob said:

The gas board are saying as the boilers nearly 20 years old its needing replaced its getting serviced

20 years ago for gas boilers there was a choice of a condensing boiler, or a 'normal' boiler;

1. If you have a normal boiler (commonly fitted at that time as the cheapest type and well proven), you would make significant savings changing to a modern condensing boiler.
2. If you already have a condensing boiler (and it is working OK and reliable), modern ones are only slightly more economical (better controls, better pump and electrical bits, and variable firing rate are likely to be the main changes).

Changing to a condensing (which is I think the only type you can get now) can save quite a lot (maybe 30%) - but does (or at least may depending on your system) have 'downsides'.  It's worth understanding these;

1. A condensing boiler gets much better efficiency by allowing the water content in the combustion exhaust gasses to condense to water inside the boiler.  This recovers heat that would be lost up the flue in a conventional gas boiler.  However ......
2. To work properly, the water returning from the radiators to the boiler needs to be cooler, below around 50C is needed - cooler still is better still.  To do this the hot water flowing from the boiler to the radiators is also cooler, and this means that the existing radiators may be too small and need either replacing by larger, or changing to double convector types.  That in turn might need larger pipes - depending on what is fitted now - to allow for more water flow.
3. The condensing boilers need a condensate drain.  These need careful location/routing because they can freeze in cold weather which is a very common breakdown because many are badly installed.  Ideally they should be located indoors.
4. The flue gasses (being much cooler) tend to have a big steam plume in cold weather which many don't like if the flue is near a path, or boundary.

20 minutes ago, Bigbob said:

i know a farmer who has a heat pump and moans about it but its a big old farm house

Big old farm houses are usually difficult to heat - and a heatpump may not have been the best choice (depends on what else was available and what type).

[discobob]

20 minutes ago, Bigbob said:

We have insulation between the beams on the floor of the loft then its floored its rather nice painted green and got fields ect on it , its where  the previous owner played with his trains , Then i put fibreglass insulation between the roof beams and held it up stapling garden fleece over the top . My mates often said its warm in here you got the heating on ?. Then we only run the heating from mid October to March . The gas board are saying as the boilers nearly 20 years old its needing replaced its getting serviced on friday so we will see but if they still have trouble accessing parts i still think another boiler will cover my needs i know a farmer who has a heat pump and moans about it but its a big old farm house 

look at Intergas - can work with heatpumps in a hybrid top up solution if it all changes in the future regards well you know... - Daikin use them (rebadged) in their hybrid solution - mine has been plumbed in in a way - with the use of ballcock valves which means that we can add a cylinder etc.. if and when required....