Air Source Heat Pumps

How do air source heat pumps work?

Air source heat pumps take in outside air, which can be as cold as -20 degrees C. The heat energy in the air is transferred to a sealed system of refrigerant inside the unit. This refrigerant is pumped through a compressor, which compresses the gaseous refrigerant. As the gas is compressed, it is heated up, much like when air is compressed. It is this heat which is transferred to the central heating water, to be used in the home. The cycle of refrigerant cooling and then being compressed is completed many times to give a constant heat.

What are the design considerations for my home?

The air source heat pump is a fairly bulky item, and will require one metre of access at the front for maintenance. They produce a small amount of noise (like a fridge freezer), and are often placed beside a garage or down the side of the house. A free flow of air will be needed for the pump to work, so positioning between trees or large plants is avoided.

People talk about 3 phase electrical supply for the unit to work. What are these?

3 - Phase electrics are often needed for heat pumps that have high KW inputs. This is because of the current they draw from the grid. Without 3 phases lights may flicker on and off during startup of the machine. A normal home operates by taking one line from the phase of the power lines above your home. 3 phases is 3 lives taken which increases the amount of current available. This supply may cost around £1500 to install and is not always available so check before deciding on a powerful air source heat pump. Air source heat pumps installed by Solo Heating Installations only require a 3 phase supply if the output you require is above 12kw.

What else will I need for this system to work?

Air source heat pumps work more efficiently at lower operating temperatures. For this reason it is advised to have underfloor heating throughout your home. They will also need a buffer tank. This will stop them cycling on and off in a short space of time. As a final step, the hot water will need a backup energy source such as an immersion heater. The backup heat can come from many different renewable sources, including solar panels and wood burning stoves.

You can find more information on Air Source Heat Pumps at the Heat Pump Association Website

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Ground Source Heat Pumps

How do ground source heat pumps work?

Ground loops are installed in the ground and are filled with an antifreeze mixture. The liquid inside the loops is pumped around by a large pump located at the ground source heat pump unit. As the water is pumped around the ground loops, the heat energy in the ground is transferred to the water. Once the heat energy reaches the heat pump, the energy is transferred to a sealed system of refrigerant inside the unit. This refrigerant is pumped through a compressor, which compresses the gaseous refrigerant. As the gas is compressed, it is heated up, much like when air is compressed. It is this heat which is transferred to the central heating water, to be used in the home. The cycle of refrigerant cooling and then being compressed is completed many times to give a constant heat.

What must I consider before purchasing a Ground Source Heat Pump system from Solo Heating Installations?

The pumps within the unit will create a low humming noise that may cause a nuisance if it’s positioned in a garage below a bedroom for instance. They are often located in utility or plant rooms as they will need some access for any future maintenance.

Ground source heat pumps work more efficiently in different ground conditions. Some earths will conduct heat to the ground loops better than others. Depending on the ground type around your property, we will have to increase the loop length to compensate. A full ground survey is completed by us at design stage to ensure the correct loop length is specified.

People talk about 3 phase electrical supplies for the unit to work. What are these?

3 - Phase electrics are sometimes needed for heat pumps that have high KW inputs. This is because of the current they draw from the grid. Without 3 phases lights may flicker on and off during startup of the machine. A normal home operates by taking one line from the phase of the power lines above your home. 3 phases is 3 lives taken which increases the amount of current available. This supply will cost around £1500 to install and is not always available so check before deciding on a ground source heat pump. Ground source heat pumps installed by Solo Heating Installations only require a 3 phase supply if the output you require is above 12kw.

I've heard of high prices for these systems, what will everything cost?

As a very basic guide, a ground source heat pump using the horizontal loop type system will cost upwards of £10,000. You will then have to pay for the ground excavation works. This is normally undertaken by the ground worker whilst the plant machinery is on site. If boreholes are used expect to pay around £3500 per hole with a normal installation comprising of one.

You could save up to 75% or more in energy bills per year and cut your carbon emissions significantly. Ground source heat pumps have a working life of above 25 years so you will be future proofing your property against fuel cost rises. With the right technology behind them, ground source heat pumps can provide a working basis to create a truly zero-carbon or even carbon plus home.

I've heard that the slinky coil design can create problems with ground freeze?

It is well documented that slinky coil design ground collectors or compact collectors can cause problems with ground freeze. Because the energy extracted by the coils is taken from a relatively small area, radiant energy from the sun can't keep up with the heat transfer into the pipes, so slowly the ground around the coils will loose heat that it cannot regain. It has been seen in some circumstances that the ground completely freezes over in the areas of the coil. We will only install horizontal ground collectors (including open loop) or bore hole type designs.

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Exhaust Air Heat Pumps

How do exhaust air heat pumps work?

Solo can install two different types of exhaust air heat pumps. The first class (NIBE 200P and 360P) will take warm stale air from the bathrooms, kitchen and utility rooms within the home, and extract that air through a series of ducts run within the floor and walls. The heat energy within the air is passed over heat exchangers within the unit, which transfer the energy to refrigerant. This refrigerant boils and evaporates (whilst still sealed in the unit at all times), and once this refrigerant is in a gaseous state, it is compressed. As this gas is compressed it creates heat, much like when air is compressed, and it is this heat which is transferred to the hot water and heating system.

The step up from the 200P and 360P units is the 410P units. These extract air from the stale air areas of the home, but at the same time, transfer some of this recycled heat to fresh incoming air from the outside. This fresh air is circulated through a separate duct system to the livable areas of the home. These include the living rooms and bedrooms. The 410P unit will save more Kwh's of energy per year, but will cost around £900 more to install.

Do these systems work with underfloor heating ?

The exhaust air heat pump provides hot water for heating. This is most efficient when installed together with a full underfloor heating system. As the unit produces hot water at lower temperatures more efficiently than at higher temperatures, it is best installed with underfloor heating.

Will they provide hot water as well ?

The units will cover all of the hot water and heating requirements for the home, in the one neat unit. If the heating load is unusually high, or the hot water needs are high, there are in-built immersion heaters that boost the hot water. These immersion heaters are also used to boost the hot water itself up to the 55 degrees we want to store it at. The heat pump contributes to most of the hot water heating, up to around 45 degrees, and at that point it is more efficient to give that short extra boost to the hot water, to bring it up to 55 degrees.

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Heat Recovery Systems

There are many upgrades available for heat recovery systems, are these a worth-while option?

Upgrades to the heat recovery systems that Solo provide include better filters, climate cooling and air conditioning.

Upgraded filters are an excellent choice for allergy sufferers as they will filter an even greater amount of particles out of the air. The filters we offer are electrostatic filters that work at higher efficiencies to the standard ones.

Climate cooling is a step down from full air conditioning. It will go a long way to cool the air as it passes into the system during the summer months to ensure your property remains ventilated but cooled at the same time. Expect to see a 10 degree C reduction in the incoming air temperature, compared to the actual outside air temperature.

The climate conditioning upgrade will give you powerful control over the temperature of the air coming into your home through the heat recovery system. It will allow you to bring the fresh ventilated air into your property at a much lower temperature that the outside to give that air conditioned coolness.

Where will the air lines and grilles be installed?

It is most common to run the flexible air ducts through voids in joists and voids in the loft space. Often the unit will be located in the attic eaves, with the lines running around the house and dropping down to each level. The grilles themselves can be positioned on the ceiling or even the walls.

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Thermal Stores

My architect has advised me to go for a thermal store, what design considerations are there?

Thermal heat stores work on the principles of heat layering into different temperature zones within the cylinder. It is for this reason that the cylinders need to be tall, roughly around 2 metres. They will therefore need to be positioned in a room with clearance for the cylinder and any adjoining pipework.

There are so many different thermal stores available to buy; how will I know which is the right one?

The key difference to the thermal stores is the amount of external tapings available for the different heat sources. It is always advisable to buy a thermal store with the ability to install a renewable technology in the future in case you decide to. Many renewable energies such as Air Source Heat Pumps will require a certain amount of water in the system to eliminate any high pressure or cycling problems. They will also have to be sized correctly to meet the demands of the hot water draw-offs to the property. Solo Heating Installations will be able to advise you on the correct thermal store for your system at the design stage.

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Solar Panels

Do solar panels have a good payback period?

Solar panels are currently one of the best renewable energies in terms of payback. We can install a solar system for around £3400, and because these systems can save you £400 per year, they have a good pay back period of around 8 years. Once you factor in the £400 government grant available, and the steady increase in fuel prices, the period reduces significantly.

My local authority have insisted on using solar panels for my new build?

As popularity for solar panels increases, local authorities are in some cases making it compulsory for homeowners to install solar panels for their new home. If you find this is the case, we would suggest installing an unvented hot water cylinder of thermal store to dock the solar panels to.

I wouldn't like the look of solar panels on my roof, is there another place to mount them out-of-site?

There are now many different possible mounting positions for solar panel collectors apart from the roof. Solo Heating can now install panels on flat roofs with special mounting 'A' frames, or even have panels mounted to the side of an exterior wall. It is always a consideration to which way the sun faces to determine the location of your panels. A SW to SE angle is always preferred and for them to be away from cast shadows is a necessary requirement.

Solar panels come in two different designs, the evacuated tube design and flat plate. The evacuated tubes are more efficient but are often not chosen because people prefer the look of the flat panel designs.

Do solar panels require any maintenance ?

Solar panels require an annual check of the antifreeze fluid levels which you can do yourself. Other than that, there are few moving parts and little to go wrong.

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Underfloor Heating

I've had experience or heard of older systems having poor controllability?

With the older underfloor heating systems, there was a long delay in systems getting warm and keeping the systems at the desired temperature was difficult. This has all changed with modern systems being highly controllable, now surpassing standard radiator systems in terms of efficiency and comfort. Think of the entire floor to your home being one large thermal mass that emits heat evenly around the floor. Each room or zone has its own thermostat, so control is extremely accurate.

Underfloor Heating costs more than standard radiator systems, is it a good option?

There is no short answer to this as every situation is different. For many of the new renewable or green technologies to operate at an efficient level, underfloor heating is preferred. This is because underfloor heating operates at lower temperatures; units like ground and air source heat pumps operate at lower working temperatures so underfloor heating is the ideal solution.

Underfloor heating is also known to increase the value and salability of your home as homeowners see it as a very desirable option. Quite often people will choose underfloor heating on the ground floor and have radiators upstairs. To lay the pipes on the ground floor within the screed is always cheaper than running them for the 1st floor.

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Wood Burning Stoves

Can I dock wood burning stoves to a thermal store ?

It is possible to dock wood burning stoves with a hot water charging pack or back boiler to thermal stores. The thermal store will need to be of a design which accepts wood burning stoves, and the coil rating will need to correlate to the output on the wood burning stove. There are a few other design requirements to ensure safety when docking wood burning stoves. The primary one is a heat dump radiator which is usually installed in a un-inhabitable room or in the loft. The radiator is used to dump surplus and excess heat from the wood burning stove. Once the cylinder is up to temperature, and the wood burning stove is not giving its heat to the cylinder, it needs to radiate this heat safely otherwise the operation of the wood burning stove itself is affected.

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