Air Source Heat Pumps

Current RHI tariff rate is 10.49p / kWh renewable heat (up to 31st March 2019).

GETTING AN AIR SOURCE HEAT PUMP FROM BETTER PLANET – FROM FIRST DISCUSSION TO FINISHED PROJECT

Initial contact

The initial contact is often on the phone and we try to establish if an air source heat pump makes sense from a financial and technical point of view. Heat pumps makes sense for most new built projects. For retrofits, heat pumps makes most sense for properties not connected to the gas grid. If you are connected to the gas grid, you should only consider a heat pump if your property is well insulation and you have a heating distribution system allowing you to operated the system with low flow temperatures. This typically means underfloor heating and/or generously sized radiators.

First meeting – feasibility discussion and site assessment

If the initial discussion is promising, we usually meet up with our client on site. We discuss how the Renewable Heat Incentive works, the importance of insulation and a suitable heating distribution system. We also look at possible locations to the heat pump itself and other required units, typically a buffer tank, control unit and hot water cylinder. We assess the heat pump location in relation to neighbours. In some cases, planning permission is required if the heat pump is close to another property. During this meeting we will you a first price indication based on our preliminary assessment.

Detailed site visit to collect information for heat loss calculation, radiator assessment and draft EPC

In order to put you in a position where you can take an informed decision about the project, we need to know the heat loss of the property (so we can specify the right size heat pump), we need to assess the radiators (to identify if you will need any upgrades). We also do a draft EPC which makes it possible to predict tariff payments from the Renewable Heat Incentive scheme. Back in the office, we produce a room by room heat loss report, a radiator assessment and the draft EPC. We charge £200 plus VAT for these reports for domestic properties up to 400 m2.

Quotation, confirmation of the project and design

We draw up a full quotation with detailed information meeting all requirements from the MCS scheme. Once the quotation is accepted, we will issue a deposit invoice. Once the deposit is paid, we start the project design. This results in a Project Planning Pack, a bespoke document outlining all the details of your project; schematics, layouts, material lists etc. Once the design is approved, we agree on installation dates and order the required material.

Installation, commissioning and hand over

An air source heat pump for domestic use is usually installed in a couple of days depending on the complexity of the system. Once installed, we commission the system in line with MCS rules and manufacturer’s recommendations. We explain to you how the system works and we produce a handover pack including all documents you need such as operating manual and MCS certificates. Most of our clients apply for tariff payments under the Renewable Heat Incentive Scheme. It is a relatively simple application and we are happy to support you with any information you need.

Operation and service

Once the system is handed over, we support you with any advice and service you require.

GROUND SOURCE, AIR SOURCE, WATER SOURCE OR EXHAUST AIR SOURCE ?

We install three types of heat pumps: Brine to water, air source and exhaust air.

Brine to water collects its energy from the ground (boreholes or horizontal loops) or from water (lake, pond or river).

Air source collects energy from outdoor air and exhaust air collects the energy from indoor air.

In the table below we have ranked the different solutions in terms of efficiency (A is best) and cost (A is most expensive) assuming that the respective system has been designed correctly.  The efficiency of heat pump systems depend critically on design. Incorrect sizing can result in poor efficiency for all types of systems.

 

Type of heat pump

Source of energy

Efficiency (COP)

Cost

Brine to water

Ground – boreholes

A

A

Brine to water

Ground – horizontal

C

B

Brine to water

Water (pond, lake, river)

B

C

Air source

Outdoor air

D

E

Exhaust air

Indoor air

E

D

 

So what are the pros and cons of the different alternatives?

Ground Source

Boreholes

Advantages

  • Requires less space than horizontal loops.

Disadvantages

  • Boreholes are expensive.

Horizontal

Advantages

  • Less expensive than a borehole installation.
  • More efficient than air source for space heating.

Disadvantages

  • Makes a big mess if done in a garden.
  • More expensive than air source..

Water source – pond, lake or river

Advantages

  • Typically less expensive than ground source.
  • Better efficiency than horizontal. Possibly better than a borehole installation, especially if it is moving water.

Disadvantages

  • Most people don’t have access to water as an energy source.
  • Might require permission from the Environmental Agency.

Air source

Advantages

  • Less expensive than ground source.
  • Best options if there is no space for ground loops
  • Perfect if you have an outdoor pool and need heating in the summer.

Disadvantages

  • All air source heat pumps makes a certain noise.
  • Might require planning permission in some cases.

Exhaust air source

Advantages

  • Suitable for flats
  • Low cost.
  • Perfect to meet planning requirements

Disadvantages

  • Only feasible in relatively small, very well insulated dwellings.

Why is ground source more efficient than air source?

Typically the main advantage of ground source over air source is that the ground is warmer than the air during the winter when most heating is needed. This makes it possible to obtain better efficiencies (COP’s) with ground source. The average undisturbed ground temperature over the year reflects the average air temperature, i.e. around 10-12°C in the UK. The deeper you go the smaller the seasonal variation around this average.  Once a collector pipe is installed for a ground source heat pump, it starts to extract heat and the temperature around the pipe decreases. This means that the brine (the liquid in the collector pipes bringing energy from the ground to the heat pump) will be colder than the natural ground temperature. A short collector loop brings down the temperature more than a longer one. “Good practice” for loop design dictates that the loop should be long enough for the brine temperature not to fall below 0°C during winter. For this reason collector loops must not be undersized. Ground source heat pumps with undersized collectors can be less efficient that air source heat pumps which defeats the whole object.

Having said that, ground source heat pumps with correctly sized collectors have a better efficiency over the year than air source.

HOW MUCH ENERGY WILL I PRODUCE?

Normally, heat pump installations are designed to produce all the heating energy needed for the property down to the design outdoor temperature (typically -3°C). In other words, the heating output will match the heat loss of the building plus whatever is required for hot tap water.

For a well designed system, in a property with good insulation and a low temperature heating distribution system, it should be possible to get an average COP of 3. This means that for each unit of electrical energy put in, the heat pump produces three units of heating energy. In such a system 2/3 of the energy output originates from “free energy from nature” and 1/3 originates from electrical energy.

FREQUENTLY ASKED QUESTIONS

1.Why do heat pumps work best with underfloor heating?

The lower the flow temperatures to the central heating system, the higher the efficiency and the heating power output of the heat pump. Well designed underfloor heating systems operates at considerably lower temperatures than traditional radiators and are therefore ideally suited to work with heat pumps.

2. How are heat pumps sized?

We size heat pump systems to meet the heat losses from your property at design outdoor temperature. The design outdoor temperature depends on the location. For south east England it is typically around -3 degrees. If the heat pump is used for domestic hot water, it will affect the sizing as well. A room by room heat loss calculation is always required in line with MCS requirements.

3. Are heat pumps suitable for hot tap water production?

Most heat pumps produces hot water at a maximum temperature around 55oC which is lower that what is obtained with a traditional boiler, but still high enough for domestic use. In order to achieve the right performance in terms of the available amount of hot water and temperatures at the tap points, special attention has to be made when it comes to choosing the hot water cylinder, insulation of pipes etc. We do recommend an immersion heater in the cylinder for top up in order to achieve higher flexibility and the possibility to sterilize against Legionella. The efficiency of the heat pump when used for hot tap water is lower than when it is used for space heating. Therefore there is no real saving in running costs compared to a condensing gas boiler fed by gas from the grid.

4. How efficient are ground source heat pumps?

For a well insulated house with a well designed underfloor heating system, around 4 kW of heating power can be achieved for each kW of electrical power used. The ratio of heating power and the electrical power is called Coefficient of Performance (COP). The COP depends on the quality of the heat pump but also to a large extent of the design of the central heating system, design of the ground loops and the insulation level of the property.

5. Can I retrofit a ground source heat pump in to an existing property?

In many cases you can, but if the insulation is not that good and existing radiators are sized for a gas- or oil boiler, you might find that the radiators are not capable of heating up some of the rooms in the property to the temperatures you want in the winter. To get around this you might have to upgrade some radiators or keep you old boiler as a back up for the coldest days. It may also be cost prohibitive as you will need a lager system to offset heat losses. The running cost of the heat pump will also be higher if existing radiators are used rather than low temperature radiators or underfloor heating.

6. What are the pros and cons of air source versus ground source heat pumps?

Provided that the ground loops have been well designed, a ground source heat pump is more effective than an air source heat pump when it is cold outside, i.e. when most of the heating is needed. Air source heat pumps are more effective the higher the outdoor temperature, which is why they are ideal for heating outdoor swimming pools. The main disadvantage of ground source heat pumps is the requirement to have ground loops. The ground work makes ground source installations more expensive than air source installations, especially if boreholes are required. However, the higher cost of a ground source installation is offset by the higher tariff payments under the Renewable Heat Incentive Scheme (RHI). For this reason, ground source is always a better financial option than air source for a client willing to pay a higher upfront cost and ready to take a long term view.

EQUIPMENT: HEAT PUMPS

Better Planet specifies bespoke systems and will recommend heat pumps suitable for individual projects.  For most of our projects we specify heat pumps for the leading European heat pump manufacturer Nibe (www.nibe.co.uk). The main reason why we specify Nibe are:

  • Best warranties in the market – 7 years parts and labour when installed by a VIP installer (which Better Planet is)
  • Excellent and client friendly controls
  • Option to connect the units to internet for remote controls and diagnostics
  • Air source units with very low noise level

Ground Source Heat Pumps

 

NIBE

F1145 / F1245 / F1345

 

Air Source Heat Pumps

 

NIBE

F2040 / F2300

 

Exhaust Air Source Heat Pumps

WHY HEAT PUMPS?

Heat pumps use free energy from ground, air or water outside to produce space heating and hot tap water. Correctly designed and for the right kind of property, heat pumps can deliver both energy savings and carbon reduction. Correctly sized, heat pumps can produce all required heating and hot water.

The “right kind of property” for a heat pump is a well insulated property outside of the gas grid with a heating distribution system able to operate at relatively low temperatures (typically under floor heating or over sized radiators).

PLANNING REQUIREMENTS

Ground source or water source heat pumps

The installation of a ground source heat pump or a water source heat pump on domestic premises is usually considered to be permitted development, with no requirement for planning permission. If you live in a listed building or a conservation area you should contact your council to check on local requirements.

For water source heat pumps, you should contact the Environment Agency if it is an open loop system (water taken from one area and released in another). For closed loop systems, you don’t need permission.

Air source heat pumps

The installation of an air source heat pump on domestic premises is normally considered to be a permitted development, If the proposed location for the outdoor unit is close to a neighbouring property, you should check with the planning department in your council.  The same applies if your property is listed, you live in a conversation area or an area of outstanding natural beauty.

Other conditions to be met:

• Development is permitted only if the air source heat pump installation complies with the Microgeneration Certification Scheme Planning Standards or equivalent standards.

• The volume of the air source heat pump’s outdoor compressor unit (including housing) must not exceed 0.6 cubic metres.

• Only the first installation of an air source heat pump would be permitted development, and only if there is no existing wind turbine on a building or within the curtilage of that property. Additional wind turbines or air source heat pumps at the same property require an application for planning permission.

• All parts of the air source heat pump must be at least one metre from the property boundary.

• Installations on pitched roofs are not permitted development. If installed on a flat roof all parts of the air source heat pump must be at least one metre from the external edge of that roof.

• Permitted development rights do not apply for installations within the curtilage of a Listed Building or within a site designated as a Scheduled Monument.

• On land within a Conservation Area or World Heritage Site the air source heat pump must not be installed on a wall or roof which fronts a highway or be nearer to any highway which bounds the property than any part of the building.

• On land that is not within a Conservation Area or World Heritage Site, the air source heat pump must not be installed on a wall if that wall fronts a highway and any part of that wall is above the level of the ground storey.

In addition, the following conditions must also be met. The air source heat pump must be:

• used solely for heating purposes.

• removed as soon as reasonably practicable when it is no longer needed for microgeneration.

• sited, so far as is practicable, to minimise its effect on the external appearance of the building and its effect on the amenity of the area.

You may wish to discuss with the Local Planning Authority for your area whether all of these limits and conditions will be met.

SERVICE AND MAINTENANCE

Heat pumps are relatively maintenance free. We used to recommend a yearly service of our heat pump installations, mainly to make sure that brine pressure has not dropped and that there is no air in the heating system.  All our new installations now come with an automatic brine top-up (brine to water installations) and a de-aerator in the heating system, there is usually no need for a yearly check up.

Our recommendation now is not to leave it more than three years between services. Having said that, most of our heat pump installations come with an unvented cylinder which requires a yearly service for safety reasons under the G3 regulation.  As we are on site anyway to check the cylinder, many of our clients ask us to check the heat pump at the same time for peace of mind.

PRICES AND RETURNS

Air Source

For most normal size domestic properties, the price for design, supply and  installation of an air source heat pump including a cylinder and a buffer tank is in the range of £10,000 – £15,000 including 5% VAT. Typically between 40% and 60% of this cost is recovered through tariff payments over 7 years under the Renewable Heat Incentive Scheme (RHI).

Ground Source

The price of a ground source heat pump depends on the size of the system and how the heat is collected from the ground. Boreholes are more expensive than horizontal ground loops. Some of our clients prefer to organise the ground works themselves, others prefer that Better Planet takes responsibility for the whole project. As an indication, the price for a 12kW system (typical for a new built, medium sized property) can vary from around £19,000 (ground works excluded) to £32,000 (including boreholes). These prices include 5%VAT. For a ground source installation, the client will typically recover between 80% and 120% of the project cost through tariff payments over 7 years under the Renewable Heat Incentive Scheme (RHI).

General points to consider:

  • You will save on your running cost if you replace electrical heating, oil or LPG
  • It you replace a gas boiler connected to the grid, you should only expect savings on the running costs if your property is well insulated and you have a low temperature heating distribution system (under floor heating and/or oversized radiators)

IS MY PROPERTY SUITABLE?

To put it simply, heat pumps are suitable for well insulated properties outside of the gas grid with a heating distribution system able to operate at relatively low temperatures (typically under floor heating or over sized radiators).

The downside of heat pumps is that they consume significant amounts of electricity. As electricity from the grid is both expensive and has high carbon content, there is no guarantee of any overall advantage over traditional heating unless the project is carefully designed and the property is suitable.

The efficiency of a heat pump is determined by its COP (Coefficient of Performance). The COP tells how many units of heating energy you get out of the heat pump for each unit of electrical energy you put in. The higher temperature at which the energy is collected from outside, the higher COP. The higher temperature of the warm water produced by the heat pump, the lower the COP.

Drafty and poorly insulated buildings require high temperature in the heating distribution system to compensate – low COP!

Radiators sized for a gas- or oil-boiler requires high temperature heating water– low COP!

Better Planet will always do a site visit before advising you on a heat pump system. We will give you honest advice and discourage from using a heat pump if the property is not suitable.

WHY BETTER PLANET?

  1. Extensive experience and know how
  2. Solid and well documented design and project planning
  3. Friendly and competent installers
  4. Value for money: Competitive pricing based on high volume procurement for both domestic and commercial projects
  5. We only use high quality components with outstanding warranties from well known manufacturers
  6. Our MCS certification, our membership in RECC and the fact that we are part of the Deposit and Warranty Insurance Scheme gives you peace of mind as a consumer