This new build development in Clevedon (Somerset) has been built to the latest building regulations. The Mitsubishi Ecodan W85 air source heat pump with a 180L heat pump optimised hot water cylinder was specified.

What Is an Air Source Heat Pump?

Air source heat pumps are becoming increasingly popular in the UK, having been a common sight in parts of Europe for decades already.

They are notably widely used in Scandinavia, where winter temperatures fall to well below zero for much of the time.

Heat pumps use the refrigeration cycle to move heat against its natural direction of travel. The second law of thermodynamics states that heat always flows from hot to cold, and never spontaneously in the opposite direction.

Heat pumps use electrical energy to compress refrigerant fluid and pump it around the system through a series of stages that allow the refrigerant to absorb heat from the cold side of the system (the air outside), concentrate that heat and then move it inside where it is distributed around the building.

They are incredibly efficient, particularly when compared with traditional forms of heating. The efficiency comes from the fact that they move heat, rather than generate heat directly like an electrical resistance heater would do.

Moving heat in this way, using the principles of the refrigeration cycle, means that heat pumps typically output up to four times the amount of heat energy compared to the electrical energy used by the system.

This concept is expressed as a ratio called the Coefficient of Performance (COP). A heat pump that outputs four units of heat energy by using a single unit of electrical energy would have a COP of 4.

Underfloor Heating

This setup is complemented by a Heatmiser wet under floor system using the traditional method of 16mm PEX pipe buried in screed and radiators for the first floor.

Underfloor heating is an excellent way to make best use of heat pumps. This is because heat pumps perform most efficiently at relatively low temperatures as their coefficient of performance is impacted by higher temperature differences between the cold side of the system and the warm side.

This means that using low temperature heating such as underfloor heating improves the efficiency of a heat pump system.

The reason for this is that the same amount of heat transferred into the living area by a standard hot water radiator, which is relatively small but at a high temperature, can be transferred using a much lower temperature but larger surface such as an entire floor.

Low Temperature Heat Pump

In the past, heat pumps have been criticised for not being able to cope with very low outdoor temperatures. This is not a problem for modern heat pumps, which can operate efficiently down to well below zero.

The award winning Mitsubishi ECODAN air source heat pump has been specifically designed to operate in ambient temperatures as low as –20˚C. The heat pump has also been awarded the Quiet Mark for its ultra low noise levels meeting the requirements under Permitted Development and factory coated to protect against salt corrosion in coastal locations.

Heat Pump Supplies Hot Water

Another myth associated with heat pumps is that they are not able to produce hot water that can be used for washing and bathing in the home. This is incorrect and the myth probably arose due to improperly installed heat pumps.

Capable of storing domestic hot water at 60˚C the system also utilises weather compensation to modulate the heating flow temperature increasing the Seasonal Performance Factor (SPF) and Coefficient of Performance (COP)

It is the preferred choice for housing developers looking to meet Code 4/5.

Due to the MCS accreditation of the installer, the end user was able to claim over £4500 in domestic RHI payments over the next 7 years.

Inverter Driven Heat Pump Compressor – Quiet and Efficient

Heat pumps using rotary compressors used to be a little noisy and would cycle on and off regularly because they only operated at a specific speed.

Modern inverter-driven compressors function much more precisely and can ramp up the compressor speed as required. They can run very fast when initially heating a room but then slow right down to the rate required to maintain comfort.

As a result they operate much more efficiently and more quietly than their old-fashioned rotary ancestors.

The inverter allows the system to vary the speed of the compressor matching output to load requirements resulting in increased efficiency.

• Low start current (5A)
• Low Noise 14kW 53dBA nominal
• Low Noise Mode 7°C/46dBA

If you are interested in installing a heat pump of your own, why not read our article on how to find a heat pump installer that can do the job for you?

Can an old, poorly insulated building be retrofitted with a heat pump?

A question that I hear being asked all the time is whether an air source heat pump can properly heat an old building that predates modern building standards.

The accepted wisdom is that an old building such as this will be far too draughty and poorly insulated for a heat pump to be capable of providing sufficient heat to maintain a comfortable interior temperature.

However, this case study is living proof that old buildings can indeed be retrofitted successfully with heat pump technology. Not only that, but the cost savings and carbon emissions savings can be quite significant, particularly when the government incentive schemes are factored in to the calculations.

Case Study

This was an exceptionally interesting job, which entailed the design and installation of an air source heat pump system to replace an existing oil fired boiler and ducted air heating system in an old church.

In partnership with Low Carbon Exchange and MBL Consultants the company commissioned have provided a cost effective and viable heating solution whilst also maintaining the historic integrity of the building.

Using the latest Clivet WBAN 105kW Air source heat pump with twin compressors and built in inverter driven smart pumps the system is capable of delivering 60˚C effortlessly to the emitter circuits.

The combination of Jaga fan assisted radiators and a Uponor wet under floor system maintains a balanced and comfortable environment with a fully programmable and weather compensated control system.

The Church was also in the process of claiming the Non Domestic RHI tariff which provided a revenue for the following 20 years.

How does an air source heat pump work?

An air source heat pump collects heat from outside a building using a refrigerant fluid, which is a type of gas that has thermodynamic properties that allow for the efficient operation of the refrigerant cycle. It then moves the heat inside, transporting it in the refrigerant, at which point it makes that heat available for heating the building.

The refrigerant cycle is a scientific process that uses a series of steps, including compression and condensation to effectively make use of electrical energy to move heat energy around the system. In the case of heat pumps, the movement of heat is from the outside of a building to the inside.

Underfloor heating

The means of transmitting heat into the building in this case is underfloor heating. Underfloor heating is particularly suited to use with heat pump systems because heat pumps operate more efficiently at lower temperatures.

Underfloor heating can operate at these lower temperatures thanks to the large surface area that is available for the transfer of heat from the water in the underfloor heating pipes, through the screed and into the internal space of the building.

Think of it like this. To heat a building, you can either have a very hot heat source with a small surface area for heat transfer, such as a fireplace, or you can have a lower temperature heat source that transmits a smaller amount of heat per metre squared of surface area. The trick is that the small amount of heat per square metre soon adds up across the entire surface are of the floor, thereby heating the building effectively.

Summary

This case study shows very well that an air source heat pump is perfectly capable of heating an old, poorly insulated building.

Steps were taken to improve the insulation and heat demand of the church, but these were not prohibitive.

Making use of underfloor heating is a very good way to ensure the heat pump system operates efficiently, thanks to the low temperature of such heat delivery systems.

Combined with the government incentives, this scheme makes for good value for money over the long term.

This exclusive new build development in Bigbury on Sea (Devon) has been built with no expense spared. To meet the standards required for an A rated energy efficient house a Mitsubishi Ecodan W85 air source heat pump with a 210L heat pump optimised hot water cylinder was specified. This is complemented with a Uponor wet under floor system using the traditional method of 16mm PEX pipe buried in screed and diffuser plates for timber floors.

The award winning Mitsubishi ECODAN air source heat pump has been specifically designed to operate in ambient temperatures as low as –20˚C. The heat pump has also been awarded the Quiet Mark for its ultra low noise levels meeting the requirements under Permitted Development and factory coated to protect against salt corrosion in coastal locations.

Capable of storing domestic hot water at 60˚C the system also utilises weather compensation to modulate the heating flow temperature increasing the Seasonal Performance Factor (SPF) and Coefficient of Performance (COP)

It is the preferred choice for air source heat pump installers and housing developers looking to meet Code 4/5.

Inverter Driven Compressor

The inverter allows the system to vary the speed of the compressor matching output to load requirements resulting in increased efficiency.

• Low start current (5A)
• Low Noise 14kW 53dBA nominal
• Low Noise Mode 7°C/46dBA

This air source heat pump system has been designed and installed to replace an old oil fired AGA with back boiler. Due to the existing radiators not being capable of working at the new design of temperature of 45˚C, all the existing emitters were replaced with new Stelrad K2 radiators with thermostatic valves. In addition to the radiator upgrade the kitchen was fitted with a Myson kick space heater due to the limited wall space and the conservatory is heated with a Dimplex Smartrad (Fan assisted).

The system is controlled by the new Mitsubishi FTC5 controller with weather compensation and the MELCloud for access via the internet or your smart phone.

In addition to the Mitsubishi Ecodan W85 air source heat pump 4kW of Solar PV was also fitted using the latest Solar Edge technology with micro inverters. The PV on average reduces the running cost by a further 25%. It is expected that the customer’s annual fuel bill will be reduced by 70%.

Not only are the fuel savings huge but the customer is also entitled to the FIT for PV, netting nearly £20,000 over the next 20 years and the Domestic RHI payments totalling £6388 over the next 7 years.

This client was looking for a firm to provide a renewable energy solution to replace their existing electric storage heaters. After conducting the building heat loss calculations and looking at the available Domestic RHI payments the logical choice was a Mitsubishi Ecodan air source heat pump. The system was designed with a 300L Joule stainless steel heat pump optimised cylinder and 200L buffer tank. The new FTC 5 controller and MELCloud allows internet access to all of the heat pumps settings.

As the property used storage heaters, new distribution pipe work was fitted throughout which was split in to 2 independent heating zones. A combination of Polypipe overlay under floor, radiators and a Dimplex Smartrad provides all the home’s space heating requirements.

Upon completion a new EPC was provided to calculate the Domestic RHI payments which totalled £10,977 over the next 7 years. As part of the installer’s ongoing customer support service they returned to the property 4 weeks later to check system operation. Over the month of November this 4 bedroom property cost £47 to provide all of the homes heating and hot water. This is 300% lower than the previous electric storage heaters.

A heat pump company was asked by their client to provide a renewable energy solution to replace the existing oil fired boiler. After conducting the building heat loss calculations and looking at the available Domestic RHI payments the logical choice was to use 2 Mitsubishi Ecodan air source heat pumps in cascade (master and slave). This means the heat pumps are enabled based on the load conditions.

The buffer tank supplies the existing under floor heating system and the hot water is pumped vis a secondary return to the tap outlets. Pre insulated quad pipe connects the air source heat pumps to the plant room.

Combined with inverter technology the system is optimised for part load efficiency. The system was designed with a 400L Joule stainless steel heat pump optimised cylinder and 200L buffer tank. The new FTC 5 controller and MELCloud allows internet access to all of the heat pumps settings.

Upon completion a new EPC was provided to calculate the Domestic RHI payments which totalled £12,835 over the next 7 years. These figures are on top of the fuel saving and user friendly control system.

A brief story from our editor here at Heat Pumps Scotland on the experiences of a friend of his in fitting a heat pump system to a large extension.

The Story

I recently caught up with an old friend whom I have known since we were at school together. He now lives in Chester and has recently completed some building work on his house.

We got chatting about his project and I was interested to hear that it included an air source heat pump. Naturally I was keen to find out more and asked him whether he would mind sending me a few photos and telling me about his experiences with the heat pump so that I could share them on the website.

He willingly obliged and I now get to share his story with you.

The Project

The project was designed to give him and his family more space in their main kitchen and dining area. Previously they were a bit cramped and had to dance around each other a bit at the busy times of day when they were all getting ready to leave the house and in the evening when they sat down to eat together.

The room was also very cold, having been done on the cheap by the previous owner who neglected to provide adequate insulation. This is something that had to change. Although it doesn’t usually get as cold as Altnaharra, Chester can get down to well below freezing in the depths of winter and my friend’s heating struggled to heat the kitchen zone of his house.

And this was the main problem, you see. The rest of the house, being better insulated, was normally quite warm, even when it was brass monkeys weather outside. The dilemma he was faced with was either to turn up the heating to warm up the kitchen and make the rest of the house uncomfortably warm, or just live with the cold kitchen. This tended to be less of a problem in the evenings when the oven and kitchen hob were adding to the overall heat in the room. However, first thing in the morning, at the time when many of us tend to feel the cold particularly keenly, the problem was especially bad.

Insulate First

One of the first bits of advice that anyone considering installing a heat pump is likely to hear is “fix your insulation first”. As a reader of this website I expect you already know this, but poor insulation will make your heat pump work far too hard to heat the room. It will be less efficient as a result and in may cases you would be better off installing a conventional boiler. By the way, condensing combi boilers are exceptionally efficient these days, achieving around 90% efficiency when new.

Being that my friend was building a new extension to make his kitchen and dining area bigger, and in the knowledge that the new part of his building would be very well insulated, he looked at the options available to him for heating.

The Options

Although this was to be an extension and therefore not benefiting from the blank slate that a new build would offer (ground source heat pumps often make it to the short-list with new builds), there were still plenty of options to choose from. The way his family was planning to use the new space meant that they would often have a need to boost the temperature in the kitchen dining room without wanting to heat the rest of the house. One option might be to install an Aga, but that would have been on all the time and his house is typically not occupied during the day while the family are out at work and school. That would be a lot of money spent heating an empty house.

Another option could have been a gas fire or wood burning stove but these were ruled out because of the space they would have taken up and also due to safety concerns with the possibility of young children burning themselves on the hot surfaces.

Heat pumps appeared to be a strong option because they can achieve very high efficiency, do not have the same safety issues as open fires or wood burning stoves and are very controllable. The advantages of heat pumps over these other options convinced him that would be the right choice.

The choice was therefore between a ground source heat pump and an air source heat pump. There was no river or pond nearby so water source heat pumps were a non-starter. A ground source heat pump was ruled out because of the disruption digging up the garden and the fact that it would have been overkill for the minor heating issue that was being faced. For these reasons, the decision was taken to go with an air source heat pump.

The Result

In the end, he went for a Fujitsu Inverter model (the Fujitsu R410A to be precise) and is very pleased with the result. In the morning, the first person up and into the kitchen flicks the heat pump on for a few minutes and by the time the cereal is in the bowl, the room is “toasty warm”.

Not only is my friend and his family now nice and warm on those cold winter mornings, but their fuel bills are reduced, despite having increased the size of their home.

As you can see from the pictures below, the heat pump fits unobtrusively into their living space and quietly does its job.

If you have any questions about this little story, let me know and I’ll do my best to answer.

You might also be interested in the case study in Scotland where a ground source heat pump was retrofitted to a tower house with amazing results.