Air Source heat Pump

Peterweb

New Member
ASHP's are quite popular in Sweden even up here in the north since they are comparatively cheap and provides a noticeably better efficiency than direct heating even down to -20.
With that said though most people nowadays are switching to geothermal heat pumps which pretty much always manage a 4 to 5 times efficiency gain over direct heating..

Thanks for the insight. I am in northern france and am looking to install either an air source hp or a more expensive system that pumps from our aquifer 140 m below the ground and uses a water to water exchanger. Is this the same as your geothermal?
 

Peterweb

New Member
Both types of heat pump ground and air are good, but the delivery of that heat is also a factor, well insulated homes work well because the operating temperature in the delivery system is low, my water temp in my underfloor heating rarely goes over 30c, so it’s vey efficient it’s actually 5 star rated that’s due to the design of the delivery system my underfloor heating, If I had tried radiators and tried to imitated the heating style of an oil boiler where I ramp up my heating rapidly so require very hot water to flow rapidly I would have a rubbish system, as heat pumps like to provide low temps at high efficiency and high temps at low efficiency.
My heating when on runs 24/7 it measures the return temp of the water from the underfloor heating and with the use of a heat curve and an outside temp gauge, runs my heating no room stats or other tech. My pumps run on low settings and as the rooms cool they effect the water temp and the heat pump runs to top it up as needed. Using just the heat pumps controller.

My ground temps have never been below freezing. So my return water has never been below freezing either, in 7 years.

If you have a large heat load then what ever you run it on it will be expensive but if you have a large heat load with a heat pump you need a great delivery system to get the best from them.
My house is not passive rated, but it either is or could be, I rarely turn the heating on until November (it’s not yet on this year and I haven’t lit any fires either). The passive heat my house creates from cooking, etc, and solar gain from windows can cover a lot of my heating, the heat pump only gets turned on for heating because I don’t light a fire every day, when it really gets cold, and it’s just a 5kw wood burner in my living room it’s no boiler stove.

Another big win are heat recovery units that and good air tightness, mine result was a 1 which was the best my council had ever tested you need below 10 to pass building regs in 2012, the next nearest was a 1 room flat, which got 1.1 (mine was a 300m2 three story detached house.)

Re thé ashp and insulation. I have heard this before but I don’t understand why this is any more relevant to ashp versus oil boiler etc. The problem of heat loss due to lack of insulation impacts both systems equally surely?. My current oil boiler will need to work harder in a poorly insulated house just like the ashp.
We have a large chateau in rural northern France, and in winter we do not attempt to heat the whole chateau. Only bedrooms and living areas that are occupied are heated unless there is a risk of pipes freezing but that is rare in Normandy. So whilst we have a large potential area to heat, we do not plan to size up any new heating system for the whole area. Instead we will be keeping the oil boiler as a backup to boost the system during colder periods.

But back to my original point. Any heating system will be more expensive to run in poorly insulated spaces no matter how big they are. An ashp’s running costs will go up during colder months as will my oil boiler. At the end of the day, it is surely about heating energy in versus that energy being lost, no matter the source of that energy.

The ashp’ s seem to like to run at a lower temp , according to those that have them. This I don’t understand. If ashp can run in Sweden down to -20c then surely that same boiler in Normandy where it’s rare to go much below -3 c would be able to heat water to a much higher temp. After all it will be extracting heat from much warmer air . That energy will be used to heat the water to a higher temp surely ? Or is there some inbuilt temperature limiter?

If I understand it correctly, the energy extracted from the air , is directly proportional to,the volume of air that the ashp sucks into its exchangers. More air in, more heat generated at any given air temp. If a ashp can heat water to say 35 c in Sweden then surely its capable of heating water to 50 c in Normandy where there is much more energy in the air comparatively. Our boiler operates at around 50 c in Normandy currently. So if the ashp can get the water to 50c most of the time, then my current systems pumps will still be able to use that water generated from the ashp in the same way it does from my oil fired boiler.
We are not particularly well insulated I would say, but our current heating is effective . It is simply not feasible to insulate a large chateau effectively. All I am trying to achieve is to lower the running costs by replacing the oil as much as possible.
 

Dave645

Member
Arable Farmer
Location
N Lincs
Re thé ashp and insulation. I have heard this before but I don’t understand why this is any more relevant to ashp versus oil boiler etc. The problem of heat loss due to lack of insulation impacts both systems equally surely?. My current oil boiler will need to work harder in a poorly insulated house just like the ashp.
We have a large chateau in rural northern France, and in winter we do not attempt to heat the whole chateau. Only bedrooms and living areas that are occupied are heated unless there is a risk of pipes freezing but that is rare in Normandy. So whilst we have a large potential area to heat, we do not plan to size up any new heating system for the whole area. Instead we will be keeping the oil boiler as a backup to boost the system during colder periods.

But back to my original point. Any heating system will be more expensive to run in poorly insulated spaces no matter how big they are. An ashp’s running costs will go up during colder months as will my oil boiler. At the end of the day, it is surely about heating energy in versus that energy being lost, no matter the source of that energy.

The ashp’ s seem to like to run at a lower temp , according to those that have them. This I don’t understand. If ashp can run in Sweden down to -20c then surely that same boiler in Normandy where it’s rare to go much below -3 c would be able to heat water to a much higher temp. After all it will be extracting heat from much warmer air . That energy will be used to heat the water to a higher temp surely ? Or is there some inbuilt temperature limiter?

If I understand it correctly, the energy extracted from the air , is directly proportional to,the volume of air that the ashp sucks into its exchangers. More air in, more heat generated at any given air temp. If a ashp can heat water to say 35 c in Sweden then surely its capable of heating water to 50 c in Normandy where there is much more energy in the air comparatively. Our boiler operates at around 50 c in Normandy currently. So if the ashp can get the water to 50c most of the time, then my current systems pumps will still be able to use that water generated from the ashp in the same way it does from my oil fired boiler.
We are not particularly well insulated I would say, but our current heating is effective . It is simply not feasible to insulate a large chateau effectively. All I am trying to achieve is to lower the running costs by replacing the oil as much as possible.
Hi
I take your point on insulation, but don’t forget these systems are expensive far more so than there oil counterparts.
So size of the system is linked to heat demand and that’s linked to insulation. Large size large price.

It’s always better value to insulate first. As that can reduce the cost of the system you need.

Extending on that by type.
GSHP are different to air, they have a limited resource, the ground coil, to bring energy into the house with, so this is why is insulation very important to GSHP systems, it’s down to the size of the system needed judged on the heating demand, and the size of the loop, so the instal cost of the system is vastly more expensive.
So insulation is always the best option first get the house as good as you can then size the system.

Air source, are a little different while less efficient and costing more to run especially in low temps ie high demand times where they can fall to levels where efficiency drops back to nearer 1:1 for 1:2 over the GSHP version in very low temps. They don’t suffer from limited input energy, limits of the GSHP have ie the ground loop.


Also note high demand heating requires higher running temps in your radiant system, (also less efficient) to offset heat losses, and bigger air source heat pumps maybe you will need multiple, so making the system more expensive to install, that also effects the electric supply demand of your system, if you have 30kw of heat pumps running to heat a big cold space, can your electric supply actually take that. 24/7 on top of your other loads?


Another point is, Sweden has some of the best insulated homes out there like triple glazing etc, as nearly standard, so they can install small heat pumps so they are cheap.

While I cannot say if your home is suitable for a heat pump of any type, limping your current system on or just directly replacing it with a new one if it’s on it’s last legs and insulating the rooms you heat with the vast amount of money you will save over fitting a very large heat pump system. May be the better use of your money.
Insulation is always a better return on your money that better heating, until your at passive levels, which are easy to find.
It’s your money and your choice, but cost up a system and ask some professionals to take a look.
Heap pump systems are not cheap. heat pump systems will be big money, and still cost you an arm and a leg to run.

In your position I would be looking to heat with wood in the limited rooms in question with modern wood burning stoves, while a chore they can be cheap to run if you can source the wood at off peak times ie anyone chopping down trees and cutting it and drying it yourself. Just chose room sealed stove with direct air supplies to avoid large drafts.
Open fires are very poor and to be avoid at all cost if possible.

I don’t envy your trouble in making these choices. Good luck.

While in Sweden they may have one air-source heat pump, for the whole house you may need one for each room. That’s all down to insulation levels.
 
Last edited:

Frankzy

Member
Location
Jamtland, Sweden
Thanks for the insight. I am in northern france and am looking to install either an air source hp or a more expensive system that pumps from our aquifer 140 m below the ground and uses a water to water exchanger. Is this the same as your geothermal?

It's very similar but not exactly the same, I assume you would drill down to the aquifer and submerge the loop into it. (Or would you literally pump up the aquifers water?)

Normally you'd drill down anywhere from 120 to 250 metres into the rock and place the loop in the shaft, the shaft quickly fills with water which is heated by the surrounding rock and in turn heats the loop.
 

scotston

Member
clearly two threads over lapping now. But the principles and mistakes of heat pump design still seem to be a mystery to most. The basic principle of thermodynamics where heat flows from a hot source to a colder is the main driver. This and the handy relationship between temperature and pressure. The energy that is being used is in the flow medium either air or brine (water and antifreeze underground). The flow rates of both are fixed by the fan and the pumps respectively. The total energy available to extract is therefore based on the temperatures of the mediums. For air this varies with ambient, with ground this varies but is buffered by the fact that the soil takes a long time to react, ie a season. By spring time the ground will be substantially cooler than in autumn but has a whole spring and summer to recharge. That's why it's called a solar array. If you specify too small an array relative to the size of the energy removed, clearly the ground will freeze. Don't. An underground aquifer or borehole is still a fluid that is massively insulated from ambient and therefore gives you a steadier output. But in the case of borehole simply a compromise between space and cost. Avoid if you can. The colder the source fluid for both air and ground the worse the efficiency. But the efficiency is much worse if you demand high flow temperatures from either unit. Head to http://johncantorheatpumps.blogspot.com/2014/03/getting-best-from-underfloor-heating.html to see how the curve is biased toward improved efficiency if you have a cold source fluid but low flow temperature. This is where insulation and radiated specification comes in. If you use radiators, they are relatively poor emitters of energy and work best with high flow temps unless you increase the radiator surface area. Big fat ones typically running at 50degC flow. Similarly the heat loss in a house is clearly worst in winter and if you have either small or too few radiators or too small an underfloor heating system then you need higher flow temps to make up the losses. Reduce the losses with insulation works. Have a densely fitted underfloor heating system all serve to lower the required flow temp and vastly improve overall system efficiency. Even in cold temperatures. My ground floor only, underfloor ASHP system runs around 30degC flow in winter with a typical CoP of 3. It uses a scroll compressor to reduce the power requirement of the unit as it approaches its load target. Typically running at 1.8kw providing 6kw of heating at 30DegC and 2.2kw providing 48degC DHW. Passive house, highly insulated. My air tightness was 0.5 air changes per hour - through good design rather than expensive materials. The air handling unit retains 93% of the heat and passes this on to the fresh and very cold incoming air. This keeps the house fresher than any normal house with a very low humidity. If you're too hot open a window, makes no odds to the system. I have a 6kw wood burner that lives in the 50% glazed living room. The heat from this travels (eventually) into the air handling unit and is distributed throughout the house. I tend to run the ambient air in the house through the day at 19degC using the underfloor and then put the fire on at night, this switches off the underfloor heating. 3 logs gets me 21degC, 5 logs and it's boxer short time. Here endith the lesson.
 

honeyend

Member
We have air source with 9kw of solar panels, the panels pay for any electric bought in. We use no other fuel.
For a lot of people our house would be too warm, its about 22C. Even with the heating off overnight and a frost it on it only drops to 19C. We have no heating upstairs except for an electric heater in the bedroom which cuts in when its below 18C. I was brought up with jackfrost on the inside of the windows so I do not like it too chilly.
As well as thick insulation we have thick walls, so heat is retained and we have a fair amount of solar gain, but I am glad we do only have a lot of glass on the shady side of the house or else we would fry. We have two Velux to let out excess heat in summer, as well as for ventilation. When they did the EPC it was A+, with no fancy gagets. I like to be able to open a window.
I like it because there is very little tempreture variation from room to room, even the ones not regularly in use, the pipes that carry the heated water to the bedrooms also keep those rooms at about 19C in winter.
The only negative I would say is although we employed people who had previous experience of under floor heating and air source, the plumbing was fitted incorrectly, three plumbers later, all with previous experience, and no long term solution, we resorted to emailing Panasonic photos, and their head technical person pointed out the were bits missed out, and some of it fitted upside down so its had a home made none experts bodge, and now works better.
 

Peterweb

New Member
It's very similar but not exactly the same, I assume you would drill down to the aquifer and submerge the loop into it. (Or would you literally pump up the aquifers water?)

Normally you'd drill down anywhere from 120 to 250 metres into the rock and place the loop in the shaft, the shaft quickly fills with water which is heated by the surrounding rock and in turn heats the loop.

No the water comes from the aquifer into a heat exchanger inside the building.
 

Highland Mule

Member
Livestock Farmer
No the water comes from the aquifer into a heat exchanger inside the building.

That's an awful lot of energy wasted in pumping - if it was a closed loop of down into the aquifer then the pumping costs should be much less - the fluid going down will displace that coming up and the only energy needed is for circulation.
 

Walton2

Member
We have air source with 9kw of solar panels, the panels pay for any electric bought in. We use no other fuel.
For a lot of people our house would be too warm, its about 22C. Even with the heating off overnight and a frost it on it only drops to 19C. We have no heating upstairs except for an electric heater in the bedroom which cuts in when its below 18C. I was brought up with jackfrost on the inside of the windows so I do not like it too chilly.
As well as thick insulation we have thick walls, so heat is retained and we have a fair amount of solar gain, but I am glad we do only have a lot of glass on the shady side of the house or else we would fry. We have two Velux to let out excess heat in summer, as well as for ventilation. When they did the EPC it was A+, with no fancy gagets. I like to be able to open a window.
I like it because there is very little tempreture variation from room to room, even the ones not regularly in use, the pipes that carry the heated water to the bedrooms also keep those rooms at about 19C in winter.
The only negative I would say is although we employed people who had previous experience of under floor heating and air source, the plumbing was fitted incorrectly, three plumbers later, all with previous experience, and no long term solution, we resorted to emailing Panasonic photos, and their head technical person pointed out the were bits missed out, and some of it fitted upside down so its had a home made none experts bodge, and now works better.
That’s just about the setup I would like here....planning 3 conversions of old stone buildings...possibly on ‘district heating scheme’ total floor area 350sq m. Would you think I would be sensible do go down that route...FITs different now....am sort of hoping panels keep getting cheaper,so it might stack up without subsidy. Insulation being very important.
 

Peterweb

New Member
That's an awful lot of energy wasted in pumping - if it was a closed loop of down into the aquifer then the pumping costs should be much less - the fluid going down will displace that coming up and the only energy needed is for circulation.

Interesting. I was told that the energy to pump up the water was relatively insignificant. It makes sense that it would be much less in a closed loop situation.
 

will l

Member
Arable Farmer
We have a need to pump from a bore hole around 10cubic metres of water per hour all winter to fill an irrigation reserve, It is coming out of the bore hole at 11 degrees centigrade, is there enough heat in it to be worth extracting?
any opininions gratfully recieved.
 

Exfarmer

Member
Location
Bury St Edmunds
We have a need to pump from a bore hole around 10cubic metres of water per hour all winter to fill an irrigation reserve, It is coming out of the bore hole at 11 degrees centigrade, is there enough heat in it to be worth extracting?
any opininions gratfully recieved.
Absolutely, a heat exchanger can easily take 3 degrees which would give you the equivalent of 3.5Kwh of heat per cubic metre.
so you are looking at 35 kw of heat at a minimum probably a fair bit more
 

Loftyrules

Member
Location
Monmouth
Sorry if it's been covered but has anyone installed a hybrid air source heat pump that combines air source with an alternative source to boost the temperature?
 

Frankzy

Member
Location
Jamtland, Sweden
It is coming out of the bore hole at 11 degrees centigrade, is there enough heat in it to be worth extracting?
Groundesource heat pumps are designed to work at around freezing and still manage a good efficiency.

At 11 degrees the efficiency of a heat pump will be through the roof, I'd be surprised if the factor would be less than 6.

Sorry if it's been covered but has anyone installed a hybrid air source heat pump that combines air source with an alternative source to boost the temperature?

Not sure what you mean by hybrid heat pump but it sounds like you just want to shunt another heat source into the outlet from the heat pump which is no problem at all.
 

Exfarmer

Member
Location
Bury St Edmunds
Sorry if it's been covered but has anyone installed a hybrid air source heat pump that combines air source with an alternative source to boost the temperature?
I believe many of the domestic ones have an immersion to boost heat if needed.
All heat pumps can pull heat from sources at any temperature ( of course not possible with water below freezing) but even then the use of anti freeze in closed loop systems can make them work at cooler temps.
 

Cms

Member
Grant engineering make a hybrid heat pump, condensing oil boiler and an air source heat pump.
 

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