UPDATED: Air Source Heat Pumps/Air Con - Full Info & Guide, is it cheaper to run than mains gas?

albyota

Yes, the system would be installed as a two zone system anyway, ground and first floor zoned, if you are thinking of fitting UFH on the ground floor (digging the screed up 65-75mm), you must allow for putting at least 50mm of celotex insulation down and covering with at least 60mm screed, door openings and first step of staircase are things to be cautious of.

sparkie7203

albyota wrote: »

Yes, the system would be installed as a two zone system anyway, ground and first floor zoned, if you are thinking of fitting UFH on the ground floor (digging the screed up 65-75mm), you must allow for putting at least 50mm of celotex insulation down and covering with at least 60mm screed, door openings and first step of staircase are things to be cautious of.

Thanks - I need to go down a fair way then. That kind of puts me off UF and makes me think it would be so much easier to install rads. I know they are far less efficent though. Any comment about me comment above on cost if I did the hard work myself ? I'm a competent DIY'er and will be doing the house plumbing myself anyway. So, estimated cost of doing the ground floor (4 bedroomed conventionally sized house),doing as much I can myself ?

albyota

I would agree, retro fitting UFH is not an easy task. If you are competent at installing pipe work and hanging radiators then yes, you would be better off getting a proper heat loss calc done for each room to size the rads correctly to work at their most efficient (lowest Temp) don't ask an ordinary plumber to size rads unless he knows the formula, trying to save money by doing it yourself doesn't always work out the best way, I know, recently finished a self build, and I know a lot of things would have cost me less in the long run if I'd not been so stubborn.

sparkie7203

albyota wrote: »

I would agree, retro fitting UFH is not an easy task. If you are competent at installing pipe work and hanging radiators then yes, you would be better off getting a proper heat loss calc done for each room to size the rads correctly to work at their most efficient (lowest Temp) don't ask an ordinary plumber to size rads unless he knows the formula, trying to save money by doing it yourself doesn't always work out the best way, I know, recently finished a self build, and I know a lot of things would have cost me less in the long run if I'd not been so stubborn.

Many thanks for your advise - sensible stuff

albyota

To enable you to receive the proposed RHI, both the installer and the heat pump has to be MCS registered, so that bit cannot be changed, but you can do the rest of the work.

Andy_WSM

Had some wiring work done today, whereby the 2 heat pumps are now on a dedicated circuit on the distribution board with an energy meter added so I can keep an eye on the running costs. I had this done as I have tripped out the ring a couple of times in the past through excessive load, so taking the 2 heat pumps off will have alleviated the problem somewhat.



I use a program called "Meter Readings" on my iPhone to take regular meter readings of the electric & gas to track my consumption and have now added a third meter for the heat pumps so I'll be able to track the weekly / monthly costs of running them also.

richardc1983

Theres a new samsung system available, it allows you to use underfloor heating and fan coil units so you can use heating and cooling as you cannot use the floor coils for cooling due to condensation issues.

You can also have fast heat startup by using the fan coil units to provide heating before the system switches over to underfloor heating mode.

PDF brochure on it:

http://www.freedomac.co.uk/Resources/Samsung/Samsung%20EHS-Catalog.pdf

And some good question and answer sessions: Lots of questions and answers here about the system but covering all heat pumps in general:

How much is an air source heat pump?

The cost of the installation of an EHS system is dependent on a number of issues including: if it’s a new installation or a retro fit, the level of insulation in the house, the age of the property and where the components of the system are going to be installed.

The budget installed price for an EHS system ranges from £6k for a small system suitable for a 2 bed flat to £10K for a system suitable for a 5 bedroom house.

Please note this is for the replacement/ installation of the boiler and hot water cylinder only. These figures do not allow for other works to the plumbing and heating system in your house.

What is a heat pump?

A heat pump is just like a refrigerator at home working in reverse. The refrigerant in the system absorbs low-grade heat from the air outside like a sponge. The compressor in the system squeezes the heat out of the refrigerant increasing the temperature as it does so. This heat is used to heat the water circulating around your radiators.

What does a split type air to water heat pump consist of?

Samsung EHS is a split type system comprising an indoor boiler connected to an outdoor unit; these are connected together with 2 refrigerant pipes installed on site.

What is the difference between a heat pump and a normal fossil fuel system?

Heat pump systems are not radically different from a conventional system. They still utilise the same hot water pipe work and radiators or under floor heating system. The boiler is replaced with a hydro box, this device looks like a boiler and carries out same functions, the difference is that instead of burning fossil fuel to heat the water, this system uses a heat pump to absorb heat from the air outside and pump it into the water in the house

Can I have my old boiler removed and a heat pump fitted in its place?

in most cases yes, a survey would normally be carried out to check equipment sightings, power supply requirements and suitability of existing radiators to confirm suitability.

How does a heat pump work?

Heat pumps contain a refrigerant gas which is capable of absorbing heat even in very low temperatures, just like a sponge absorbs water. Using a pump (compressor) we squeeze this heat out of the refrigerant and into the water. The harder we squeeze (compress) the gas the higher the temperature available.

Is a heat pump efficient?

The energy the heat pump absorbs is free as it is all around us, the only work it has to do is to pump it from outside to inside, hence the name heat – pump. This process is very energy efficient, it takes approximately 300 Watts of energy to move 1000 Watts of energy into your house so for each 1kW of electricity consumed between 3kW – 5kW of heat energy can be absorbed and transferred. By contrast, conventional fossil fuel boilers produce less heat output, about 0.85kW for every kW consumed, therefore heat pumps are, eco-friendly using renewable energy reducing CO2 emissions.

Can you cool with an air source heat pump?

Some air source heat pumps can cool as well as heat. However caution should be applied when cooling with these machines, if we cool the water in the system any exposed metal components will sweat. Typically you cannot use radiators or under floor coils for cooling. Fan coil units are the best option if this is to be done effectively. Samsung EHS is the only system available which can also have air conditioning units installed which can cool or heat independently of the rest of the system.

Is it easy to operate?

The controls on these systems have many options not unlike all electronic equipment available today. In most cases these are set up and never adjusted again after commissioning. The day to day operation of the systems is generally simple, control is by a room thermostat and radiator valves just like a conventional system, any advanced settings are usually adjusted at maintenance.

Are air source heat pumps noisy?

A typical air source heat pump is silent in operation inside the house; the boiler is much quieter than a conventional fossil fuel boiler. The unit outside emits 60dBa when running flat out. This is equivalent to the noise of a typical conversation with someone 1m away. In most cases there are no problems with using this technology in high density housing applications

I've heard that air source heat pump systems aren't reliable and have maintenance issues. Is this true?

The outdoor unit (absorber) is essentially the same as an air-conditioning unit out door unit. These have been used for the last 30 years and have a proven track record if installed and maintained correctly. The maintenance involved is essentially making sure the coils are clean and free from any obstructions.

What is the lifespan of the system and is there any degradation over time?

Air source heat pumps have a life expectancy of 15 years in normal applications if maintained correctly.


How does the run cost compare between an air source heat pump and other heating systems.

in an average house (3bed semi 1000sq ft.) the heating and hot water bill for gas would be £1000 a year. this compares to £800 for a heat pump, £1200 for LPG and £1500 for oil. Heat pumps offer the lowest run cost compared to fossil fuel boilers.

Is their a risk that we will be reducing suburban and urban air temperature by installing an air source heat pump?

No

How effective/efficient are ASHPs when used to supply domestic hot water?

Air source units can deliver sanitary hot water at up to 55C even in ambient temperatures of -20C. These systems are very popular in Scandinavia where the weather is much colder than in the UK. The efficiency of the heat pump will fall as the ambient temperature falls; this is discussed in another question.

Is it true to say that heat pumps work on normal house heating i.e. radiators? Do they not work best only on low temp under floor heating?

In any heating system the lower the circulating water temperature the better the efficiency. Under floor usually operates with a water temperature of 45C, radiators operate at 55C with a heat pump and 70C with a fossil fuel boiler. Using radiators on a heat pump is the norm but in some cases radiators will need resizing to suit the lower water temperatures from the HP. We can calculate this for you.

It seems however that if mains gas were available, it may well have been the more economic solution?

Gas boilers are cheaper to buy than a heat pump system. In most cases savings in run cost of 20 -25% can be achieved over gas throughout the year. The payback period is completely dependant on your annual usage.

How does the air source heat pump compare with a conventional gas boiler on grounds on cost?

The installed cost of an air source heat pump is typically 50-100% higher than a gas boiler. Oil and LPG boiler installations are approximately the same as a heat pump installation.

What’s the additional capital costs for the various heat pump systems and the expected payback periods.

Payback periods depend on your annual energy usage. If your usage is high payback is faster than low usage properties. We can calculate this for you if you have old bills showing usage over the past 12 months.

I've heard disturbing reports that the low estimated costs of heat pump operation have in practice been too optimistic. What factors would most lead to this disparity?

In some cases the prediction of run cost have been wide of the mark, when calculating this energy use assumptions about usage have to be made especially in new build projects. If accurate energy use figures or copies of energy bills are available the accuracy of these predictions is very good. Like all software, if bad information is put in bad figures come out.

What are the typical seasonal efficiencies for air source heat pumps?

Manufacturers tend to give an energy efficiency figure for their kit at one "nominal" condition, typically 6 degree outdoors temperature and 20 degree indoor temperature. They are required to do this as part of EN14511. Generally this figure is a good indication of the sort of efficiencies you could expect over a whole year. Bizarrely there is no approved calculation method for working out whole year efficiencies so proceed with caution if figures vary from the nominal figures.

At what point does the unit become inefficient?

Air source heat pumps are designed to operate efficiently in ambient of as low as -20C, even at these temperatures the COP is over 2.

How is the COP (efficiency) of air source heat pumps affected by outside air temperature?

The COP of heat pumps is inversely proportional to the difference between the temperature of the heat source (the air or the ground) and the temperature of the water circulating round the building. If the difference is high the cop falls and visa versa. So in warm weather the COP is high and in cold it falls. See graph below. Note that reducing the circulating water temperature increases COP.

How practical is it to run heat pumps using pv or wind turbine generated electricity i.e. is 50% or more grid electricity needed?

A typical house needs a 9kW heating system, assuming a COP of 3 means the electrical energy input required would be 3kW. If you have wind or PV electricity available it can of course contribute towards this load but connecting one to the other with no help from the mains supply is not practical as supply and demand will vary unpredictably. It is possible to run the system 100% from wind power and solar PV if there is enough energy available

What is COP?

COP is the heating capacity available divided by the energy input. It is a measure of system efficiency; a COP of 2 means that for every kW of electrical energy put into the system will give you 2 kW of heat.

Where does an air pump need to be located on the external skin of the building and is there any way of concealing them/incorporating them into the fabric's exterior to please planning authorities?

The unit needs to be installed 150mm above the ground on an external wall of the building. It is essential that the unit gets enough air to breath so enclosing it will reduce efficiency. Blocking airflow with wheelie bins or plants is not a good idea. Enclosures re available and sight screens can be used. Most systems need to be installed less than 30 metres away from the boiler.

Can Air source systems be sensibly installed in loft areas, with ambient temperatures raised above outside temps, assisting COP, assuming quiet working?

Mounting the absorber in the loft is not ideal as they produce up to 10 litres of condensation per hour and must have plenty of air available. If sufficient provision for airflow is available and suitable drainage is available a loft can be used.

Heat pumps come in fixed sizes, is it best to undersize or oversize?

Under sizing the heat pump will leave you short of capacity when it is cold outside, over sizing will make the unit cycle on and off when the demand is low, I.e. spring and autumn. We try to size the systems to match the load perfectly in the coldest expected conditions.

Heat pumps require larger boilers than traditional boilers - are small systems being developed as space is always an issue within properties.?

This is not the case, the Samsung EHS boiler is the same size as a traditional combination boiler. Over time the systems will be more compact.

If heat pumps are combined with solar panels (and even PV panels) would the outputs all go into the same system or would it be best to keep solar heating to domestic hot water and heat pumps for central heating?

Our systems allow solar panels to heat the sanitary hot water when available and when not the heat pump takes over. The heating of the radiators etc does not use the solar panels.

I currently have the old warm air heating system run from a large electric boiler, which was popular in the 70's. The system works well but is very uneconomical. I would love to substitute this with an air-to-air heat source pump linked to the existing ducting. Is this possible?

This very easy to do with an air to air heat pump, there are many systems available which can work in this application

How would a heat pump be used for a domestic swimming pool installation?

In many applications we have used heat pumps to heat swimming pools. When this is done a separate heat exchanger has to be used to heat the pool, as you cannot run chlorinated water directly through the heat pump.

In terms of residential building size is there a cut off point when a Heat pump becomes more economic to install, given the additional initial capital cost, than a typical condensing gas boiler and radiators?

The only difference between a gas installation and a heat pump is the boiler itself; the radiators cylinder etc is the same. In all cases the heat pump is more expensive throughout the size range.

What are possibilities of using heat pumps to provide some initial temperature increase of water temperature (in combination with solar panels) not completely replacing boiler but reducing the temperature increase required from the boiler?

The Samsung EHS system can be used as the first stage of a heating system, to be topped up by a boiler if required.

Are reverse cycle air source heat pumps now considered as renewable?

Yes our systems are now classed as a renewable technology.

How much is an air source heat pump?

The cost of the installation of an EHS system is dependent on a number of issues including: if it’s a new installation or a retro fit, the level of insulation in the house, the age of the property and where the components of the system are going to be installed.

The budget installed price for an EHS system ranges from £6k for a small system suitable for a 2 bed flat to £10K for a system suitable for a 5 bedroom house.

Please note this is for the replacement/ installation of the boiler and hot water cylinder only. These figures do not allow for other works to the plumbing and heating system in your house.

What is a heat pump?

A heat pump is just like a refrigerator at home working in reverse. The refrigerant in the system absorbs low-grade heat from the air outside like a sponge. The compressor in the system squeezes the heat out of the refrigerant increasing the temperature as it does so. This heat is used to heat the water circulating around your radiators.

What does a split type air to water heat pump consist of?

Samsung EHS is a split type system comprising an indoor boiler connected to an outdoor unit; these are connected together with 2 refrigerant pipes installed on site.

What is the difference between a heat pump and a normal fossil fuel system?

Heat pump systems are not radically different from a conventional system. They still utilise the same hot water pipe work and radiators or under floor heating system. The boiler is replaced with a hydro box, this device looks like a boiler and carries out same functions, the difference is that instead of burning fossil fuel to heat the water, this system uses a heat pump to absorb heat from the air outside and pump it into the water in the house

Can I have my old boiler removed and a heat pump fitted in its place?

in most cases yes, a survey would normally be carried out to check equipment sightings, power supply requirements and suitability of existing radiators to confirm suitability.

How does a heat pump work?

Heat pumps contain a refrigerant gas which is capable of absorbing heat even in very low temperatures, just like a sponge absorbs water. Using a pump (compressor) we squeeze this heat out of the refrigerant and into the water. The harder we squeeze (compress) the gas the higher the temperature available.

Is a heat pump efficient?

The energy the heat pump absorbs is free as it is all around us, the only work it has to do is to pump it from outside to inside, hence the name heat – pump. This process is very energy efficient, it takes approximately 300 Watts of energy to move 1000 Watts of energy into your house so for each 1kW of electricity consumed between 3kW – 5kW of heat energy can be absorbed and transferred. By contrast, conventional fossil fuel boilers produce less heat output, about 0.85kW for every kW consumed, therefore heat pumps are, eco-friendly using renewable energy reducing CO2 emissions.

Can you cool with an air source heat pump?

Some air source heat pumps can cool as well as heat. However caution should be applied when cooling with these machines, if we cool the water in the system any exposed metal components will sweat. Typically you cannot use radiators or under floor coils for cooling. Fan coil units are the best option if this is to be done effectively. Samsung EHS is the only system available which can also have air conditioning units installed which can cool or heat independently of the rest of the system.

Is it easy to operate?

The controls on these systems have many options not unlike all electronic equipment available today. In most cases these are set up and never adjusted again after commissioning. The day to day operation of the systems is generally simple, control is by a room thermostat and radiator valves just like a conventional system, any advanced settings are usually adjusted at maintenance.

Are air source heat pumps noisy?

A typical air source heat pump is silent in operation inside the house; the boiler is much quieter than a conventional fossil fuel boiler. The unit outside emits 60dBa when running flat out. This is equivalent to the noise of a typical conversation with someone 1m away. In most cases there are no problems with using this technology in high density housing applications

I've heard that air source heat pump systems aren't reliable and have maintenance issues. Is this true?

The outdoor unit (absorber) is essentially the same as an air-conditioning unit out door unit. These have been used for the last 30 years and have a proven track record if installed and maintained correctly. The maintenance involved is essentially making sure the coils are clean and free from any obstructions.

What is the lifespan of the system and is there any degradation over time?

Air source heat pumps have a life expectancy of 15 years in normal applications if maintained correctly.

What is the difference in maintenance costs between ground/air source heat pumps and gas central heating?

The maintenance schedule for an air source heat pump is a little more complicated than a conventional gas boiler. You need to allow up to £250+ vat for an annual ser ice visit and up to 2 call outs for a system serving a typical 3 bedroom house. A similar service agreement for a gas boiler will be £156/ year

Efficiency cop run costs etc

How does the run cost compare between an air source heat pump and other heating systems.

in an average house (3bed semi 1000sq ft.) the heating and hot water bill for gas would be £1000 a year. this compares to £800 for a heat pump, £1200 for LPG and £1500 for oil. Heat pumps offer the lowest run cost compared to fossil fuel boilers.

Is their a risk that we will be reducing suburban and urban air temperature by installing an air source heat pump?

No

How effective/efficient are ASHPs when used to supply domestic hot water?

Air source units can deliver sanitary hot water at up to 55C even in ambient temperatures of -20C. These systems are very popular in Scandinavia where the weather is much colder than in the UK. The efficiency of the heat pump will fall as the ambient temperature falls; this is discussed in another question.

Is it true to say that heat pumps work on normal house heating i.e. radiators? Do they not work best only on low temp under floor heating?

In any heating system the lower the circulating water temperature the better the efficiency. Under floor usually operates with a water temperature of 45C, radiators operate at 55C with a heat pump and 70C with a fossil fuel boiler. Using radiators on a heat pump is the norm but in some cases radiators will need resizing to suit the lower water temperatures from the HP. We can calculate this for you.

It seems however that if mains gas were available, it may well have been the more economic solution?

Gas boilers are cheaper to buy than a heat pump system. In most cases savings in run cost of 20 -25% can be achieved over gas throughout the year. The payback period is completely dependant on your annual usage.

How does the air source heat pump compare with a conventional gas boiler on grounds on cost?

The installed cost of an air source heat pump is typically 50-100% higher than a gas boiler. Oil and LPG boiler installations are approximately the same as a heat pump installation.

richardc1983

What’s the additional capital costs for the various heat pump systems and the expected payback periods.

Payback periods depend on your annual energy usage. If your usage is high payback is faster than low usage properties. We can calculate this for you if you have old bills showing usage over the past 12 months.

I've heard disturbing reports that the low estimated costs of heat pump operation have in practice been too optimistic. What factors would most lead to this disparity?

In some cases the prediction of run cost have been wide of the mark, when calculating this energy use assumptions about usage have to be made especially in new build projects. If accurate energy use figures or copies of energy bills are available the accuracy of these predictions is very good. Like all software, if bad information is put in bad figures come out.

What are the typical seasonal efficiencies for air source heat pumps?

Manufacturers tend to give an energy efficiency figure for their kit at one "nominal" condition, typically 6 degree outdoors temperature and 20 degree indoor temperature. They are required to do this as part of EN14511. Generally this figure is a good indication of the sort of efficiencies you could expect over a whole year. Bizarrely there is no approved calculation method for working out whole year efficiencies so proceed with caution if figures vary from the nominal figures.

At what point does the unit become inefficient?

Air source heat pumps are designed to operate efficiently in ambient of as low as -20C, even at these temperatures the COP is over 2.

How is the COP (efficiency) of air source heat pumps affected by outside air temperature?

The COP of heat pumps is inversely proportional to the difference between the temperature of the heat source (the air or the ground) and the temperature of the water circulating round the building. If the difference is high the cop falls and visa versa. So in warm weather the COP is high and in cold it falls. See graph below. Note that reducing the circulating water temperature increases COP.

How practical is it to run heat pumps using pv or wind turbine generated electricity i.e. is 50% or more grid electricity needed?

A typical house needs a 9kW heating system, assuming a COP of 3 means the electrical energy input required would be 3kW. If you have wind or PV electricity available it can of course contribute towards this load but connecting one to the other with no help from the mains supply is not practical as supply and demand will vary unpredictably. It is possible to run the system 100% from wind power and solar PV if there is enough energy available

What is COP?

COP is the heating capacity available divided by the energy input. It is a measure of system efficiency; a COP of 2 means that for every kW of electrical energy put into the system will give you 2 kW of heat.

Where does an air pump need to be located on the external skin of the building and is there any way of concealing them/incorporating them into the fabric's exterior to please planning authorities?

The unit needs to be installed 150mm above the ground on an external wall of the building. It is essential that the unit gets enough air to breath so enclosing it will reduce efficiency. Blocking airflow with wheelie bins or plants is not a good idea. Enclosures re available and sight screens can be used. Most systems need to be installed less than 30 metres away from the boiler.

Can Air source systems be sensibly installed in loft areas, with ambient temperatures raised above outside temps, assisting COP, assuming quiet working?

Mounting the absorber in the loft is not ideal as they produce up to 10 litres of condensation per hour and must have plenty of air available. If sufficient provision for airflow is available and suitable drainage is available a loft can be used.

Heat pumps come in fixed sizes, is it best to undersize or oversize?

Under sizing the heat pump will leave you short of capacity when it is cold outside, over sizing will make the unit cycle on and off when the demand is low, I.e. spring and autumn. We try to size the systems to match the load perfectly in the coldest expected conditions.

Heat pumps require larger boilers than traditional boilers - are small systems being developed as space is always an issue within properties.?

This is not the case, the Samsung EHS boiler is the same size as a traditional combination boiler. Over time the systems will be more compact.

If heat pumps are combined with solar panels (and even PV panels) would the outputs all go into the same system or would it be best to keep solar heating to domestic hot water and heat pumps for central heating?

Our systems allow solar panels to heat the sanitary hot water when available and when not the heat pump takes over. The heating of the radiators etc does not use the solar panels.

I currently have the old warm air heating system run from a large electric boiler, which was popular in the 70's. The system works well but is very uneconomical. I would love to substitute this with an air-to-air heat source pump linked to the existing ducting. Is this possible?

This very easy to do with an air to air heat pump, there are many systems available which can work in this application

How would a heat pump be used for a domestic swimming pool installation?

In many applications we have used heat pumps to heat swimming pools. When this is done a separate heat exchanger has to be used to heat the pool, as you cannot run chlorinated water directly through the heat pump.

In terms of residential building size is there a cut off point when a Heat pump becomes more economic to install, given the additional initial capital cost, than a typical condensing gas boiler and radiators?

The only difference between a gas installation and a heat pump is the boiler itself; the radiators cylinder etc is the same. In all cases the heat pump is more expensive throughout the size range.

What are possibilities of using heat pumps to provide some initial temperature increase of water temperature (in combination with solar panels) not completely replacing boiler but reducing the temperature increase required from the boiler?

The Samsung EHS system can be used as the first stage of a heating system, to be topped up by a boiler if required.

Are reverse cycle air source heat pumps now considered as renewable?

Yes systems are now classed as a renewable technology.

Andy_WSM

Thanks Richard, interesting read, although I find this surprising:

What is the difference in maintenance costs between ground/air source heat pumps and gas central heating?

The maintenance schedule for an air source heat pump is a little more complicated than a conventional gas boiler. You need to allow up to £250+ vat for an annual ser ice visit and up to 2 call outs for a system serving a typical 3 bedroom house. A similar service agreement for a gas boiler will be £156/ year

Really?

The maintenance costs for mine have been precisely £0 the last couple of years. I am perfectly capable of carrying out a visual inspection of the fan coils and changing a filter. One of the FAQs prior to this even says the units are low maintenance, with making sure the fan coils are clear the main thing to check.

p.s. Mine is well & truly in heat mode first thing in the mornings at the moment. I have it on from 5am for an hour, just to life the temperature while I am getting ready for work / showering. The Autumn chill is creeping in!

Andy_WSM

Just thought I'd update with the first capture from my Heat Pump energy meter. This shows the running costs of both heat pumps combined - hot water and heating / cooling as required.

Average daily cost currently running at £0.62, which clearly will rise as we move into Autumn.



The huge drop in the graph yesterday is because we had no electric for 13 hours due to an outage, hence, little running cost! Just hope that doesn't occur mid Winter, brrrrr!