The thermostat is a common fixture in most homes, helping to maintain an even temperature in the house all year round. In the winter, room thermostats (sometimes referred to as roomstats) prevent rooms from overheating. In the summer months, they ensure the heating system does not fire up unless the temperature of the house falls below a preset level.
How do thermostats work?
A thermostat is normally a control unit for a central heating boiler, but these days it can also control electric heating such as infrared panels. You choose the temperature that you would like the house to be at via a dial or a digital display on the thermostat. The thermostat then monitors the ambient temperature of the air and instructs the boiler/heating system to turn on or off accordingly.
If the temperature of the ambient air is lower than the requested temperature set on the thermostat, it will fire a message to the boiler to fire up and send hot water to the radiators to heat the house.
If the air temperature is too high, the thermostat will send a message to the boiler to switch off, which obviously should result in the home cooling down.
Using a thermostat will therefore ensure that the house stays at a regular temperature and rooms don’t overheat. The thermostat will ensure that the boiler keeps a constant temperature in the house, which results in an efficient heating system that will save you money on your gas bills.
How much can a room thermostat save?
A correctly-installed thermostat can save you £100s per year, however you have to know how to get the best out of it. For example, a pre-installed room thermostat can save about £65 for every degree centigrade you turn it down. Therefore if you normally have your home at 230C and then decide to turn the thermostat down to 210C, you should see energy savings of well over £100.
We have written a blog you can read here on the optimal indoor temperature, which discusses some of the common queries people have when it comes to setting their thermostat.
Thermostats do not speed up the rate of heating
One common misconception of thermostats is that if you turn up the dial of the thermostat, the room will heat up quicker. The rate at which a room heats up is dependent on the boiler, the size of the room, the size of the radiator and finally, how well-insulated the room is.
Thermostats and draughts
Roomstats are sensitive little things; if they are hit by prolonged cold draughts they will instruct the boiler to fire up. This means that they have to be positioned very carefully in the house.
For example, we have seen thermostats installed in clients’ hallways just by the draughty front door. This means that they will normally be recording a lower temperature than the actual ambient temperature of the house and will instruct the boiler to fire up, using more gas.
Thermostats are just part of heating controls
Thermostats are just one part of a home’s heating controls, which normally include a programmer and TRVs. They are designed to work seamlessly with the other components, with the thermostat overriding the programmer to prevent overheating. It is important that you don’t situate your roomstat near a radiator with a TRV because they will interfere with one another – that will mean the heating may go on and off unexpectedly.
New intelligent heating controls such as Nest take the idea of the thermostat much further. They allow you to set the temperature of the home from the other side of the world via your phone, but they also take into account things like direct sunlight, which in the past has manipulated the ambient air temperature.
To learn more about intelligent heating controls, click here.
Since many homes are unoccupied for parts of the day, there is little point in heating them if no one is there to benefit. A programmer allows the occupant to specify when the heating comes on to match their lifestyle and their heating requirements.
For many people in the UK, this simply means firing up the heating in the winter months for a couple of hours in the morning, so the house is warm when they wake up, and then firing the heating up again in the evening so the house is warm when they get home until they go to bed.
This means that the heating won’t be on in the interim times, for example during the day when they are at work, or in the middle of the night (although some people do like a warm house even when asleep!).
Programmers range massively in functionality and the choice is often dependant firstly on the type of boiler – combi or heat only. A combi boiler produces hot water on demand whilst a heat-only boiler (despite the name), produces hot water that gets stored in a hot water tank until required.
Two-channel programmers versus single-channel programmers
With a heat-only boiler, you need a two-channel system: one channel that allows you to program when the hot water is being produced and the other for the heating in the home.
For a combi boiler, you only require a single channel programmer – since you are only worried about when the heating comes on.
It is not uncommon for us to encounter boilers that have a malfunctioning two-channel programmer, where the heating and hot water are tied to one another – so when you turn the heating on, the hot water is being produced and vice-versa!
Accuracy of heating programmer
Once you have established what type of programmer you need – a single or dual channel system, then you can choose the functionality you need.
Obviously over the course of a week, people’s heating habits change. For example Monday to Friday it might be very similar, however on Saturday/Sunday, you might require the heating to come on later in the morning.
There are essentially three types of programmer that each allow you different levels of control. There are one-day programmers that allow you to specify when the heating comes on each day but every days heating pattern will be mirrored.
So with this type of programmer you might opt for something like this.
Mon – Sun 8:00am – 10:00am 14:00pm – 23:00pm
These are the most basic types of programmer and while they are simplistic so potentially good for some, in terms of energy saving they are not ideal.
The next type of programmer is the 5-2 programmer, this allows you to set two heating patterns, one for a day in the average working week, and the other for a weekend day (i.e Saturday / Sunday).
So with this type of programmer you might opt for something like this.
Mon – Fri 6:00am – 9:00am 17:00pm – 22:00pm
Sat – Sun 8:00am – 10:00am 14:00pm – 23:00pm
Depending on the type of programmer you have it may also allow you to set further time slots for the heating to come on – e.g. instead of just heating the home morning and evening, it may allow you to specify 2 hours in the morning, 2 hours at midday and then a few hours in the evening.
The most advanced (but the one than can most accurately match your heating requirements) is the 7-day programmer and most bought today would be of this type. This allows you to set heating requirements for each day of the week independently.
So with this type of programmer you might opt for something like this (based on the fact that this occupant works from home Tuesday and Thursday).
Monday 6:00am – 9:00am 17:00pm – 22:00pm
Tuesday 7:00am – 11:00am 14:00pm – 21:00pm
Wednesday 6:00am – 9:00am 17:00pm – 22:00pm
Thursday 7:00am – 11:00am 14:00pm – 21:00pm
Friday 6:00am – 9:00am 17:00pm – 22:00pm
Saturday 8:00am – 10:00am 14:00pm – 23:00pm
Sunday 8:00am – 10:00am 14:00pm – 23:00pm
The good thing about the new programmers is that they allow you to dumb down the complexity if you don’t want it – so if your heating requirements are fairly simple you may just wish to go with 5-7 functionality.
The override button
All new programmers will have an override button, which can give your heating or hot water (if you have a heat only boiler) a boost. If you are using a lot of hot water for example (and you have a hot water tank) you can hit the override button and it will fire up the hot water for an additional hour – allowing you to run more showers or baths.
Programmers working with thermostats and TRVs
You can find more information on thermostats here, but they can be used in conjunction with programmers. The programmer means that the boiler will only fire up as per the times set, however if the house reaches a certain temperature the thermostat will instruct the boiler to turn off.
Working together, thermostats and programmers and TRVs compliment each other to help you tailor your heating demands. This means not heating rooms unnecessarily and also no overheating which helps reduce heating bills.
Taking heating systems a step further you might want to consider intelligent heating control systems which allow you to monitor and change the temperature in individual rooms and learning functionality like Geofencing.
Insulated homes need thermostats – not programmers!
Even so, in reality we would advise people to also get programmers because if you are out of the property for an extended period of time it is worth having ensuring the heating comes on occasionally in winter to stop pipes freezing – the cost of which would far outweigh the energy savings!
Thermostatic radiator valves are commonly referred to as TRVs and are used to control the air temperature of different rooms – you will normally find them on the side of your radiators.
TRVs are just one of a number of heating controls, which allow homeowners to heat their homes more efficiently. If set up correctly, they allow you to have different heating zones throughout the house, despite only one centralised boiler providing the heat.
How does a TRV work?
The TRV is a self-regulating valve that works by changing the flow of hot water into a radiator. It consists of two parts, the valve head and the valve body, with the head sitting atop the body. When the room temperature changes, a capsule in the valve head contracts or expands, which moves a pin in the valve body causing it either to open or close.
If it gets too warm in the room, expansion of the capsule will cause the pin to close the valve – slowing the movement of hot water into the radiator. Likewise, if the room drops in temperature, contraction of the capsule in the valve head pulls the pin out, allowing hot water to enter the radiator once more.
There tends to be two materials used in the TRV capsules – wax or liquid. On the whole, liquid models are generally considered to be better and their price reflects this. One of their advantages is their responsiveness to changes in temperature – while the wax one is relatively slow to expand or contract, the liquid capsule will change the flow of water into the radiator far more quickly.
Costs of TRVs
A traditional TRV will cost you about £10 – 30 each.
Where not to use a TRV
There are two places that you really shouldn’t install TRVs on the radiators – the first is in bathrooms. This is because the heat produced by the bath/shower will cause the TRV to shut off (it will cause the capsule to expand), just when you need the heat from the radiator to fight off condensation.
We also don’t advise installing a TRV in the same room as your main heating thermostat. The main thermostat will link directly to the boiler, firing it up or turning it down, so by having a TRV in that room they will fight for control – if the TRV wins, the heating in your house will go off!
Smart TRVs
Nowadays you can take zonal heating control a step further with smart TRVs. These electronic TRVs are remotely controlled to constantly monitor the temperature of the room and move the pin up and down accordingly.
They can also be used with the other heating control components to create an intelligent heating system like the Heat Genius system. This obviously adds significant cost to the system, but allows you to accurately monitor and control the temperature of individual rooms in the home all from the touch of the button on your tablet computer or phone.
Are TRVs a good idea?
In properties with a decent number of different rooms, then TRVs are definitely worth considering, especially if there are rooms that are unused and therefore not worth heating in the first instance.
They can produce decent energy savings especially when part of an intelligent heating system.
It is important to maintain them though; many clients we see have non-functioning TRVs.
It is important to ensure that the valve head vents don’t get clogged by dust and other objects since this can obstruct air hitting the liquid or wax capsules that control how the TRV functions. It is also worth checking once a year that the pin in the valve body is still moving freely (these sometimes get stuck).
To do this, unscrew the valve head off the body – this should reveal the pin that moves up and down controlling the flow of water into the radiator. A spring should hold the pin fully extended above the valve – if the pin doesn’t move when you push it, you may need to replace the whole valve assembly.
If you have purchased – or are about to purchase – infrared heaters, then understanding where to put them is important to get the best results.
Infrared heating panels don’t operate like conventional convection heating, which warms air. Instead the panels emit far-infrared radiation, which travels unimpeded until it hits a solid object, which will in turn absorb the infrared and then heat up. Do not mistake infrared with harmful UV light, which is on the other side of the light spectrum – infrared is 100% safe.
The main thing to remember is that if the infrared radiation is impeded before it reaches its destination, then the object will not warm up. As a result, to get the most out of the heating panel it should ideally be fitted in the centre of the room. Or if you have a larger area and are getting a number of panels, then they should be evenly distributed in that space. The panels should be above seating areas so as not to be shadowed, which is why positioning on the ceilings is by far the most popular.
The distribution of infrared heater rays
When the panel is positioned on the wall or ceiling, the infrared radiation will travel at 45o angles in all directions. If they are in a corner and too close to a wall other than the one they are attached to, then you will be warming a small concentrated area; this is not ideal since you will be wasting potentially useful heat. For this reason it is paramount that you don’t position the panels too close to the walls: rather ‘centre’ them as much as possible.
300Watt and 350Watt panels should be at least 0.5m (1.5 feet) or more from the floor – and the larger panels (basically anything over 600Watts) should be at least 1.5m (5 feet) away. When the panels are on they will beam the infrared radiation up to 3m(10 feet). If you have higher ceilings, please give us a ring and we can discuss appropriate models to use in this instance.
If you install the panels on the walls, then you should try and position them as high as possible. Positioning them too low will almost certainly result in furniture blocking the infrared radiation, which will limit their heating.
For the smaller panels we recommend having them at least 1.0m (over 3 feet) and for the bigger panels this to be positioned 2.0m (6 to 7 feet) high. Like your radiators, the surface temperature of the panels gets to about 80oc, so do not touch or have objects too close to them.
The installation process
All our panels come with a UK plug, so you can simply plug in and go, but we recommend hardwiring them into an electric circuit where possible. This allows you to use a proper switch (like a light switch) to turn them on. It also means you can install a smart heating system for optimal efficiency. We strongly recommend a professional installation and having the panels ‘hard wired’ into your electrical system by a Part P-qualified electrician.
In terms of the installations themselves we anticipate that most customers will seek the advice and expertise of a Part P qualified electrician who will hardwire the units to a thermostat and the property circuit board. You can find out whether your electrician is Part P qualified by looking up their details on the Competent Person Register.
The infrared panels will invariably come with a frame on the back, which allows you to easily attach them to the wall. This does mean that the panels will sit about 1-2 cm off the wall.
Although the panels radiate heat from their front surface (which will get warm), the reflector technology will ensure that there is no heat being emitted out of the back. The fact they are sitting away from the wall also helps in this respect.
Most of the panels that are sold should be supplied with screws and fixings to get the panels attached to the wall or roof. We do recommend getting an electrician to fix them in position though, and hardwire them into your mains electricity rather than simply run through an existing plug socket.
When the panels are plugged in, they take about 90 seconds to get up to full heat intensity and since you don’t need to wait for the air to get warm, you should feel their effect very quickly. To stop the panels from overheating, they will modulate and come on and off as required; however we recommend having them installed with some form of thermostatic control to ensure the room doesn’t get too warm. The most basic option is a timer plug adapter, however we recommend going for a proper thermostat and programmer unit if you have the funds available.
The installation is carried out as follows:
Mark and drill the four holes, insert wall plugs and screws with eye bolts supplied, these ensure about 0.5cm spacing from the ceiling;
Tighten screws and insert the screws into the mounting profile on the reverse of panel.
Then when connecting to the wireless thermostat:
Connect a permanent 240 volt mains supply to terminals L and N in the receiver,
Connect the infrared panel neutral (blue) wire to the neutral (N) terminal in the receiver,
Connect the infrared panel live (brown) wire to the normally open (NO) terminal in the receiver,
Connect a permanent link wire between live (L) and common (C) terminals in the receiver
This will ensure that when the receiver switches the power on it will reach the panel. Please note – switch contacts alone are volt-free and will not therefore supply power directly to the panel.
Installing infrared panels in the bathroom
Good infrared panels are either IP45 or IP54 rated, which means they can also be used in bathrooms. It is worth bearing in mind that building regulations state that any electrical bathroom installations should be undertaken by a Part P qualified electrician, who in turn will complete a BS7671 installation certificate.
The pull switch or programmer needs to sit outside the bathroom. In terms of placement, the unit needs to be at least 0.6m (2 feet) from a shower or a bath. In addition if you are placing it above a washbasin, please ensure it is at least 13cm away. Again, your electrician should be able to advise and action as appropriate.
Benefits
Having your panels installed by a Part P qualified electrician will ensure that any potential risks are minimised.
Infrared rays are safe! Do not confuse them with UV, which are not.
Fit and forget technology, very little maintenance required.
Limitations
‘Shadowing’ – if there are objects inhibiting the movement of infrared rays across the room they may not work as effectively.
The thermal comfort will also depend on how well insulated your property is. The poorer the insulation, the more the panels have to work and the less comfortable you may feel as the property is naturally draughty.
Installing infrared heating
Are you thinking about installing infrared heating in your home? We have scoured the country for the best tradespeople, so that we can make sure we only recommend those we really trust.
If you would like us to find you a local installer to help install infrared heating in your home, just fill in the form below and we will be in touch shortly!
Introduction to Hot Water Cylinders
Heating
There are two types of hot water cylinders found in homes today. The newer pressurised unvented hot water tanks and the older style vented hot water tanks.
Unvented hot water cylinders
Unvented hot water cylinders were only made legal in the UK in 1986, but have since grown rapidly in popularity. In an unvented system there is no cold water tank – instead, the sealed hot water cylinder is fed directly by the cold water mains. Since they are operating at mains pressure, they offer much better flow rates, meaning your shower and bath performance should be higher.
The other major benefit is that you don’t need to maintain a cold water tank in the loft (which vented systems require). This is good news since not only does it free up space, it also removes the potential freezing issue during our long cold winter periods.
In addition, since you aren’t relying on gravity to move the hot water around the home, the unvented cylinder can be located pretty much anywhere in your property.
Other advantages of installing an unvented system include reduced noise in the system (since there is no cold water filling of the water storage cistern), and since there is no water storage cistern and the system is essentially sealed, the cold water is not at risk from contamination.
Unvented water cylinders and the water expansion issue
Since water increases in volume as it gets warm, unvented cylinders need to include a mechanism that allows the expansion to take place, thereby keeping the cylinders operating at a safe pressure.
There are two methods of allowing this expansion to take place safely. The first is the bubble top unit, which uses an internal air bubble that is produced and trapped at the top of the cylinder when it is installed. The other type is the external expansion unit that utilises an expansion vessel to contain the expanded hot water.
The major issue with unvented hot water cylinders is that since hot water flow depends on the cold water main pressure; if for any reason the mains water is turned off, your home will be without access to any hot water.
Since unvented hot water tanks operate at higher pressure than vented systems and have additional safety features installed, these cylinders need to be installed by boiler specialists who hold a qualification that complies with G3 of building regulations. This means they tend to be far more expensive to install than traditional vented hot water systems.
Vented hot water systems
Vented hot water tanks are still the most common type of hot water system found in the UK. Unlike newer unvented tanks, these copper tanks are fed by cold water from a header tank (normally located in the loft) and they use gravity to drive the hot water around the home. A vent pipe links the vented hot water cylinder and the cold water in the header tank.
As with the unvented system, expansion of warm water is still an issue, but in this case the expansion simply takes place via the vent pipe and in the header tank.
The hot water pressure tends to be governed by the height of the water tank above the tap or shower feed. This means that although on the ground floor of the home the pressure might be excellent, in rooms on upper floors the pressure will be lower. As a result, many showers in homes with vented hot water tanks use electric pumps to drive the hot water to the shower at increased pressure.
Vented hot water cylinders are far less complicated than the pressurised vented systems and for this reason they are much simpler to maintain and install. This makes them a far cheaper option when compared to the unvented system.
Most hot water cylinders are heated via an external heat source such as a gas boiler or solar thermal. In this case the hot water is heated and then travels through a copper coil in the hot water tank. The heat is then transferred from the from the external heat source to the water inside the hot water tank.
Indirect cylinders tend to be fitted with a direct backup (such as a immersion heater). Even if the boiler is broken, you can still produce hot water as and when you need it.
You can get both vented and unvented indirect systems.
Direct systems
In a direct cylinder system, the hot water is heated directly by an internal element such as an immersion heater. The hot water tends to be more expensive to produce in direct systems. Some homes have no access to gas, for example a mid-level flat. In this case they are forced to go with a direct system for their hot water, so they may choose to take advantage of Economy 7, which will give them a cheaper electricity at night to heat the hot water with.
Normally this type of cylinder would be fitted with two different immersion heaters, one for the peak electricity and one for the off-peak electricity. If this is the case, you really need to make sure that the immersion heaters are set up on the timers correctly to ensure you are paying the least possible for the hot water. There is no point heating water via your peak immersion heater during the middle of the night.
You can get both vented and unvented direct systems.
Combi boilers
We have covered combi boilers in more detail here, however it is worth mentioning that they can produce hot water for your home without the need for a hot water cylinder. While you can use electric point of use hot water heaters, gas currently is about ¼ of the price of electricity. Therefore it makes sense to use gas to heat the water as well as to carry out your heating.
The issue with combi boilers is that since they operate at mains water pressure, as soon as there is a pressure drop (i.e. more than one tap is opened in the home) then the hot water pressure is split between the two outlets. They are however ideal for smaller properties since there is no need to store hot water which is not very energy efficient.
Are you interested in getting an unvented water cylinder? We have scoured the country for the best plumbers and heating engineers, so that we can make sure we only recommend those we really trust.
If you would like us to find you a local installer, just fill in the form below and we will be in touch shortly!
Biomass boilers vs conventional gas boilers
Heating
Comparing the cost of biomass boilers with conventional boilers
Biomass boilers start at about £7,000 for a 12kW domestic version, which is sufficient to provide heat and hot water for a 4-bed house. A comparably sized gas boiler will only cost around £2500 to install. A bigger biomass boiler with an auto-feed hopper may cost closer to £12,000.
However, biomass boilers burn biomass fuel, which is considered renewable. Therefore, provided that the boiler is MCS-accredited, you will be eligible for the Renewable Heat Incentive that will pay you for every kilowatt-hour of heat produced.
In terms of the cost of fuel, the average price of wood pellets are around 4.2p/kWh which is very much in line with mains gas, while oil costs a little more at 6p/kWh. However, the price of wood pellets is likely to become more attractive going forward since gas prices have continued to rise in recent years, and this trend looks to continue. Biomass boilers are completely independent of the fluctuating import prices of foreign fuels such as gas and oil.
Also, if you are lucky enough to have a free supply of wood, then you can heat your home at zero cost.
Comparing the efficiency of biomass boilers with conventional boilers
Biomass boilers run at an efficiency of 89 – 91% (Trianco Greenflame – 91%; Angus Orlingo 500 – 92%), while the top-rated gas boilers similarly run between 88 – 91% efficiency (Baxi Duo-tec HEA 91%; Valiant Ecotec Plus series over 91%); therefore biomass boilers are comparable to conventional gas boilers.
Comparing biomass boiler maintenance with conventional boilers
If you decide to opt for a biomass boiler, you will have to feed it fuel from time to time. For example the Baxi Bioflo will need to be refuelled every 3 -4 days. Bigger biomass boilers with auto-feed hoppers will only need to be refuelled every couple of weeks. In addition, ash builds up as part of the combustion process (wood combustion produces about 0.5% – 1.5% by weight of ash) which will need to be emptied too.
A gas boiler is very much an ‘install and forget’ technology, so it is the clear winner here.
Comparing the size of biomass with conventional boilers
Biomass boilers are much bigger than conventional boilers, since they will have to have some element of an auto-feed option. In the case of the Baxi Bioflo, it is 1.2m high, while a conventional gas boiler is half the size.
The other thing is that gas tends to come from the mains gas supply via a gas pipe. A biomass boiler will need to be situated relatively close to a fuel supply, which obviously means you are going to need a decent-sized storage facility that can be kept dry and contained so there is no fire risk.
Comparing the environmental credentials of biomass boilers and conventional boilers
Biomass boilers run on biomass fuel. Biomass fuel tends to be derived from quick-growing trees and fuel grasses. Trees absorb carbon dioxide as part of photosynthesis, which is the process that allows them to produce sugars required for growth. When the trees are felled and then burnt, they release the same level of carbon dioxide that they took in, meaning that biomass is arguably a carbon-neutral fuel.
It can be argued that gas is also derived from the breakdown of vegetation, but this process takes millions of years, and we are currently using the gas at such a rate that we are getting through our supplies much quicker than it is being replenished; it is therefore not sustainable. As a result gas and other fossil fuels are not considered to be renewable, since the time scale for the process to occur is simply too long.
As a result, burning biomass is not considered particularly harmful to the environment, whereas burning gas is considered to have negative consequences.
The other thing to bear in mind is that growing crops for fuel is only okay if the land that the crops are being grown on has not historically been used to grow food. Growing fuel crops at the expense of food crops is obviously an unsustainable practise.
The final verdict – biomass versus conventional boilers
MCS-approved pellet fired or gasification biomass boilers are comparable with the most efficient conventional gas boilers and, through the Renewable Heat Incentive, they actually produce a very healthy return (provided the heat demand on your EPC is sufficient). Therefore provided you have the space to house the fuel and the boiler itself and you are happy that you are going to have to ‘feed and clean’ the boiler on a regular basis, then a biomass boiler is certainly worth considering.
Obviously they are very expensive to buy upfront, so this too is something you have to bear in mind. If you have access to cheap finance then installing a biomass boiler could actually be a no-brainer!
Benefits
Biomass boilers are more efficient than conventional gas boilers
Since they use renewable fuel, the benefit from the Renewable Heat Incentive
Limitations
Biomass boilers require maintenance – they need to be feed fuel and cleared of ash on a regular basis.
They require a greater amount of room since the units are not only bigger, you also need to store the fuel somewhere close to the boiler.
Cost
A biomass boiler might cost £7000, while a gas boiler might cost just £2500.
Installing a biomass boiler?
Are you thinking about installing a biomass boiler? We have scoured the country for the best tradespeople, so that we can make sure we only recommend those we really trust.
If you would like us to find you a local installer, just fill in the form below and we will be in touch shortly!
Air source heat pumps convert heat energy from the air to provide heat and hot water for dwellings. They run on electricity, but are incredibly efficient (in some cases 300% or more), which means that for every one unit of electricity used, they produce 3 units of useful heat.
If you compare that to a brand new boiler which is 90% efficient (1 unit of gas produces 0.9 units of useful heat), you can quickly see why these systems are so popular. In fact, if you don’t have access to mains gas, heat pumps are definitely the way to go to fulfil your heating and hot water requirements – provided you have a well insulated home, which is discussed later.
Better still, if you decide to install an air source heat pump in your home, you can also benefit from the Renewable Heat Incentive, which pays you for each unit of hot water water you produce. In some cases, the funding will cover the cost of installing the heat pump, but it gets paid over 7 years on a quarterly basis, so you will still need to find the money upfront!
The air source heat pump needs to be located outside in the open air, and uses a fan to draw air into it. This air then flows over a heat exchanger, which contains a refrigerant liquid. An evaporator uses the latent heat from the air to heat the refrigerant liquid sufficiently until it boils and turns to a gas. This gas is then compressed by a compressor, which causes it to significantly increase in temperature. An additional heat exchanger removes the heat from the refrigerant (turning it back to a liquid), which can then be used as useful heat. There are two types of air source heat pump:
Air-to-water heat pumps
Air to water heat pumps are by far the most popular. These take heat from air outside the property and transfer this to water, which can be used for space heating or as hot water for washing within the house.
Air-to-air heat pumps
These remove latent heat from the air outside the property which is then simply fed into the home through fans. This type of heat pump cannot be used to produce hot water.
Since they include fans and compressors, air source heat pumps require electricity to operate, and bearing in mind the price of electricity is approximately 15p / kWh and gas is just 4p / kWh, on the face of it, you would expect heat pumps to be far more costly to run than gas boilers.
This is not the case though – since for every kW of electricity used to run them, they provide approximately 2.5-3.5kW of equivalent useful energy (depending on the model and the temperature of the external air). This makes running costs comparable to a traditional gas boiler.
The efficiency of air source heat pumps is measured by the Coefficient of Performance, which is simply how many units of useful energy produced from each unit of electricity are consumed to operate the system. For example, if at any moment the heat pump was producing 3kW of useful heat from each unit of electricity, the CoP would be 3.
The CoP varies throughout the year, with lower figures achieved during the colder months (meaning they are running less efficiently), since there is less ambient heat available to remove from the air. This makes comparing the efficiency of different heat pump systems very difficult, so we use what is known as the Seasonal Performance Factor to compare like for like performance of models. This is the annualised CoP, taking into account the different performance throughout the year.
Air source heat pumps don’t produce boiling water
The air source heat pump does not produce the sort of hot water temperature you would associate with a gas, LPG or oil-powered boiler. With a boiler, you would expect the hot water to be heated to about 850c, while a heat pump produces water to about 550c. Trying to increase the water temperature from a heat pump beyond this requires the compressor to work harder, meaning more electricity – this in turn reduces its efficiency or coefficient of performance.
As a result, it is very important to minimise heat loss from the property prior to installing a heat pump. This includes insulating the walls, loft and ideally the floor too. This means that even though the radiators won’t get as hot (using heat pumps), the house is still heated effectively and you are not straining the heat pump – which is expensive.
When installing a heat pump, you may be required to increase the size of some of the radiators in certain rooms too. This is simply because the heat demand will not be met with the existing-sized radiators. If this is the case, you can expect to pay about £200 – £300 for each radiator that needs to be replaced (providing the pipework running to the existing radiator can be reused).
Air source heat pumps and the Renewable Heat Incentive
Heat pumps are part of the Renewable Heat Incentive scheme recently launched by the Government. It means that, if you install a renewable heating technology, you can get paid for each unit of heat you generate. RHI payment rates depend on lots of things, but you can see detailed information here.
Occasionally, but not often, the RHI payments will be enough to cover the cost of the initial outlay of the air source heat pump. Air source heat pumps normally cost between £7,000 – £10,000.In a standard property you can expect to receive a total of about £2-5,000. RHI payments are paid quarterly over 7 years, so you will need to stump up the money up front.
Things to consider before investing in an air source heat pump
Placement of air source heat pump – An air source heat pump requires plenty of space, either to mount on an external wall or to be placed on the ground. The unit needs good air flow, and foreign objects such as boxes, containers etc need to be kept well away.
Cost of air source heat pump system vs system that is being replaced – Purchasing an air source heat pump on top of an existing heating system will prove to be an expensive option; therefore we recommend considering this when replacing an old electric or old oil-fuelled system. However an electric heater will convert 1kW of electrical energy to 1kW of heat energy and an air source heat pump will convert 1kW of electrical energy into 3.5kW (almost 4kW) of heat energy.
Insulation – The air source heat pump emits low temperatures but on a consistent basis. To maximise effectiveness, ensure that your home is suitably energy efficient by installing wall insulation (either cavity or solid wall) and draught proofing. These are low cost measures that will make a big difference to your utility bills, therefore it is worth investing in them prior to replacing your heating system with an air source heat pump.
Noise of air source heat pump – An air source heat pump does make some noise when operating, as both a fan and a compressor will be in motion. The noise is approximately 40-60 decibels (depending on the system) from a distance of one metre away. So please ensure if you invest in an air source heat pump, it is not placed directly outside your bedroom window!
We have filmed an air source heat pump in motion, (don’t say we don’t treat you) so you can see for yourself how they operate.
Efficiency of air source heat pumps – Despite air source heat pumps being able to operate at -250C, the efficiency decreases as the outside temperature drops; therefore if you live in a particularly cold place, you may well need to supplement the heat pump with an additional boiler to get the hot water you require. Try a CHP boiler if you can invest additional resources. The problem may be getting the two systems to work successfully in tandem; therefore a traditional boiler could be your only option.
Local authority regulation for air source heat pump installation
Generally there are fewer restrictions from local authorities in England and Scotland when looking to install an air source heat pump (noise being the main consideration), but please check with your council and installer before proceeding. In Wales and Northern Ireland, an air source heat pump installation requires planning permission.
Benefits
As the heat pump provides the hot water for heating, there are large savings to be made on fuel bills – typically an air source heat pump can deliver up to 3.5kW of useful energy for every 1kW of energy needed to run it.
An air source heat pump can still take heat out of the air in temperatures as low as minus 20 degrees.
By installing an air source heat pump you can reduce your carbon emissions from your homes heating by 50%.
Air source heat pumps are potential income sources, if households qualify for the government Renewable Heat Incentive (RHI) scheme. The RHI is payable on an MCS ASHP installation, carried out by an MCS Accredited Installer and the payment is backdated to include any installation installed after 15th July 2009.
Limitations
Air source heat pumps can be fairly noisy, approximately 40 – 65 decibels at a distance of 1m away (however this varies by manufacturer). Look at our video below for some first hand experience.
The equipment needs to sit outside the house, so may not be suitable if there is not sufficient space.
Air source heat pumps become less efficient at extracting heat from the air when the external temperature is low, so the amount of usable useful heat they produce is less.
Cost
An air source heat pump will cost from about £7,000 to install.
Installing heat pumps
Are you thinking about getting a heat pump? We have scoured the country for the best tradespeople, so that we can make sure we only recommend those we really trust.
If you would like us to find you a local heat pump installer, just fill in the form below and we will be in touch shortly!
Ground source heat pumps use the earth as a heat source, taking advantage of the stable temperatures in the ground to provide heat and hot water for the home.
Ground source heat pumps are not a new concept and have been around since the 19th century. This technology became very popular in Sweden in the 1970s and since then units have been sold worldwide.
In the UK, there has been a sudden surge in demand in heat pumps since the launch of the Renewable Heat Incentive, which pays homeowners for each unit of hot water produced. Although rates are no longer as high as they were, they can still cover much of the initial install costs of the systems.
How do ground source heat pumps work?
A ground source heat pump system uses heat trapped beneath the ground and boosts it to a higher temperature using a heat pump. This heat is then used to provide home heating or hot water. The heat pump performs the same role as a boiler does in a central heating system, but uses ambient heat from the ground rather than burning fuel to generate heat.
Initially, a heat transfer liquid (normally glycol) is pumped through pipes buried deep in the ground. As the liquid travels through the pipework it absorbs ambient heat from the ground and warms up, before returning back to the ground source heat pump unit. Once it returns, a heat exchanger removes the heat from the liquid and it then continues to travel round and round the pipework in a continuous cycle.
The low-grade heat is transferred through the heat exchanger, then passes through a heat pump compressor which drives the temperature up to a level that is usable for heating and hot water.
How much pipework does a GSHP require?
The length of the ground loop depends on the size of your home and the amount of heat you need – longer loops can draw more heat from the ground, but need more space to be buried in.
The pipework can either be laid horizontally or vertically. If laid horizontally, the pipework tends to be buried in trenches 2-3m deep, spread over a huge surface area to ensure the heat transfer liquid has the opportunity to increase to a sufficient temperature. If the pipework is installed vertically, boreholes get drilled in to ground (at a cost of £6,000 – £8,000 for each borehole!). These need to be drilled by professionals and will regularly exceed 100m in depth to ensure that the heat transfer liquid again has the opportunity to absorb enough heat.
There are two types of ground source heat pump, and both have a few components in common – they consist of a ground heat exchanger, a heat pump and a heat distribution system (e.g. underfloor heating or radiators).
Closed loop ground source heat pump
The majority of ground source heat pumps installed today are closed loop heat pumps. As the name suggests, no outside liquid enters the loop of pipework at any point. In this set up, a sealed loop of high density polyethylene pipe is laid either vertically or horizontally in the ground. The heat transfer fluid is in a completely closed system travelling through the pipework and returning back to heat pump.
Open loop ground source heat pump
The open-loop ground source heat pump uses ground water to pump around the system; however the number of installations of this type are decreasing, mainly because you need a source of groundwater. Also an additional associated issue with the open loop ground source heat pump is that the quality of the groundwater can actually have a detrimental effect on the system.
Ground source heat pumps require electricity
The fact that ground source heat pumps run on electricity suggests that they are expensive to run (electricity is approximately 15p / kWh while gas is just 4p / kWh). However heat pumps are in fact incredibly efficient.
In fact, ground source heat pumps are even more efficient than air source heat pumps, converting each unit of electricity (required to run the pump and compressor) into 3.5 – 4.5 units of useful heat. Compare this to a brand new energy efficient boiler, which converts each unit of gas into just 0.9 units of useful heat.
The efficiency of air source heat pumps is measured by the Coefficient of Performance (CoP), which is simply how many units of useful energy are produced from each unit of electricity consumed to operate the system. With air source heat pumps, the coefficient of performance changes throughout the year. This is because since in the winter months, the unit needs to work harder (and hence uses more electricity) to drive the temperature up to an acceptable temperature.
For ground source heat pumps the coefficient of performance is relatively consistent – this means that even in the middle of winter, when hot water and heating demand are at a maximum, the GSHP should be running equally as efficiently as it does on a red hot summer’s day. This is because the temperature underneath the ground remains relatively constant all year round – and this is one of the key advantages of GSHPs over air source heat pumps.
Heat pumps do have some impact on the environment as they require electricity to run, but the heat they extract from the ground is constantly being renewed naturally, hence they are considered a renewable heating source.
Installing a ground source heat pump
The Energy Saving Trust (EST) recommends households considering a ground source heat pump to consult a Microgeneration Certification Scheme installer and only use a properly accredited professional to complete the work. During its trial, the EST found a variety of heat pumps incorrectly installed, which therefore didn’t perform as efficiently overall as they could have. It is essential to use an MCS-approved installer to qualify for the Renewable Heat Incentive.
It is important to shop around and we always recommend getting several quotes before choosing the best option for you. Studies have shown that most suppliers tend to exaggerate the savings in energy costs this system will produce.
Renewable Heat Incentive
Heat pumps are part of the Government Renewable Heat Incentive (RHI) scheme. It means that you can get paid for every unit of renewable heat you generate. You can get a significant chunk of the cost of installation back over 7 years of payments – not to mention the savings to be made from the heat pump itself. Read more on that here.
Benefits
Ground source heat pumps can lower fuel bills, especially if you are currently using conventional electric heating (saving of £420), LPG or oil (saving of £50).
Ground source heat pumps are often classed as a ‘fit and forget’ technology because they need little maintenance, and no fuel deliveries are required, however they provide space heating and hot water 24/7.
Can reduce your carbon footprint: heat pumps can lower your home’s carbon emissions, depending on which fuel you are replacing.
Limitations
Ground source heat pumps require a reasonable amount of land outside to lay the coils underground. If this is unavailable the technology will not be suitable for your home.
If you have a vertically submerged closed loop system and there is a leak, it can be difficult to gain access to.
Cost
From £13-20,000.
Installing heat pumps
Are you thinking about getting a heat pump? We have scoured the country for the best tradespeople, so that we can make sure we only recommend those we really trust.
If you would like us to find you a local heat pump installer, just fill in the form below and we will be in touch shortly!
Water source heat pumps work on a similar principle to both air source and ground source heat pumps. Instead of taking advantage of the heat in the air or the ground, they take advantage of the relatively consistent temperatures found in a body of water.
A series of flexible pipework is submerged in a body of water, such as a lake, river or stream. A heat pump pushes working fluid through the network of piping, and this fluid absorbs the heat from the surrounding water as it goes.
This working fluid is then compressed by an electric compressor, in a similar fashion to the other types of heat pump, which raises the temperature. A heat exchanger can then be used to remove the heat entirely from this working fluid, providing you with hot water that can be used for space heating (in radiators or under floor heating). It can even be plumbed into your hot water system, where a boiler can just provide the small amount of additional heat needed to bring it up to the required temperature, so it can be used for showers and baths.
Once the heat has been removed from the working fluid via the heat exchanger, it is once again pumped back through the pipework, thereby completing a continuous cycle.
The benefits of a water source heat pump
The heat transfer rate from water is higher from the ground, making them more effective than ground source heat pumps. In addition, if using a water source heat pump with a moving body of water, the heat is constantly being replaced, as new warmer water replaces the cooler water that has had its heat extracted by the working fluid.
For every 1kW of energy required to run a water source heat pump, 4-5kW of equivalent heat energy is produced which can be used to warm your home. This makes the technology more efficient than both air and ground source heat pumps.
The supply of hot water is also pretty much constant, despite being cooler in the winter; the body of water will still possess sufficient heat to enable the water source heat pump to operate in the winter. An issue only arises if the body of water completely freezes.
Unlike ground source heat pumps, where bore holes or trenches need to be dug on your plot for the piping, the pipework for a water source heat pump is relatively simple to install; it simply needs to be situated within a body of water, which should have little impact on your plot of land.
Benefits
Installing a water source heat pump is relatively easy if there is a body of water available on your property.
Water source heat pumps have a higher Coefficient of Performance than ground source and air source heat pumps: so for every unit of electricity used to operate them, they can produce more hot water.
There is little visual impact on the property, since all the pipework in the water source heat pump system is submerged within the body of water.
Limitations
A water source heat pump is reliant on there being a body of water at your property.
Usually, unless you live in a listed property or conservation area, ground and water source heat pumps are considered a permitted development. You shouldn’t need an application for planning permission. It is still worth checking with your local authority before starting installation, however.
Air source heat pumps
In England and Scotland you can install an air source heat pump (ASHP) as it forms part of permitted development. However in each region, the home owner needs to follow specific guidelines and not contravene them in order to proceed with the installation.
Unfortunately if you live in Wales and Northern Ireland, you will have to speak to your local authority to get a planning application submitted and approved before proceeding with the installation.
Air source heat pump permitted development criteria in England
Since the end of 2011, if you live in England, all heat pumps (air, ground and water) are considered a permitted development, so no planning permission is required. This was legislated in parliament to make it easier for individuals to install renewable technologies for their homes. Different outcomes apply however if you live in a listed property, conservation area or a world heritage site. We would advise you to contact your local planning authority for further guidance.
An air source heat pump is a permitted development provided numerous conditions are met:
The heat pump installation needs to adhere to the Microgeneration Certification Scheme planning standards.
The ASHP must only be used for heating
The volume of the ASHP outdoor compressor unit must not be in excess of 0.6m3
The ASHP must be sited to minimise its effect on the external appearance of the building.
You are only allowed one ASHP as a permitted development. If you also have a wind turbine or want another ASHP, then you will need to apply for planning permission.
The ASHP must be at least 1 metre from the edge of your property
An air source heat pump needs to be installed on a flat surface, be it the ground or a flat roof, however if it is elevated off the ground, it needs to be at least 1m away from the edge of the elevation.
Additional guidance in England:
If you are looking to install an ASHP on a listed building, permitted development rights are not applicable, contact your local planning authority for guidance.
On land in a conservation area/world heritage site, an ASHP must not be installed where it is visible from a highway.
If you are not using the ASHP for microgeneration, it must be removed as soon as practically possible.
Air source heat pump permitted development criteria in Scotland
In Scotland it is considered permitted development, unless installing an ASHP contravenes the following points:
It is not the only heat pump within the boundaries of your property
It is situated less than 100metres from your next door neighbour
It is visible from the main road
It sits on a world heritage site; is on scientific research land; considerably near a listed building or is near land for archaeological purposes.
You also need to make sure that the developer that is installing the ASHP speaks to the local authority and gets clearance for the size and type of unit being installed. Not all systems may necessarily comply with permitted development criteria.
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A thermostat is normally a control unit for a central heating boiler, but these days it can also control electric heating such as infrared panels. You choose the temperature that you would like the house to be at via a dial or a digital display on the thermostat. The thermostat then monitors the ambient temperature of the air and instructs the boiler/heating system to turn on or off accordingly.
New intelligent heating controls such as Nest take the idea of the thermostat much further. They allow you to set the temperature of the home from the other side of the world via your phone, but they also take into account things like direct sunlight, which in the past has manipulated the ambient air temperature.
