Types of Central Heating Systems
If you’re looking to replace your central heating system, want to know about common issues to look out for with your boiler, or simply want to know more about how your system works – then our central heating guide is for you …
There are many factors to consider when deciding on the best option to heat your home.
If you live alone in a one-bedroom flat then perhaps a rather modest 12kW combi boiler will easily handle your central heating requirements. Alternatively, if you have a large family living in a seven-bedroom country home, you may need a boiler with output of over 50kW to provide enough power to heat the water and radiators.
In all likelihood you fall somewhere in the middle, in which case you will have a number of different options ahead of you. Before going any further it’s worth checking to see what type of heating system you have currently.
Installation costs will rise considerably if you decide to switch out your current system for a completely different one; depending on the state of your current heating system this may or may not be cost-effective to do so.
Gas vs. electric systems
The central heating system is rarely something you think about. It’s something we all take for granted and just assume that when those colder mornings roll around, our boiler and radiators are up to the job.
But what’s more reliable? An electric or gas heating system? Which is cheaper to run?
In the next few sections we aim to address those questions to see if it’s worth moving over to an electric system, or vice versa.
How does a gas heating system work?
Gas heating systems are the most commonly used in the UK. This type of central heating is known as a ‘wet system’ where a gas-fired boiler heats water, which provides heating via radiators and hot water through the taps in your home – here’s how they work, step-by-step:
- A gas boiler has a continuous supply of natural gas streaming into it from a pipe that goes out to a gas main in the street
- Gas jets are directed onto a pipe containing cold water, heating it up to approximately 60 degrees Celsius.
- The water pipe makes up one small section of a large continuous circuit of pipe. This network travels right around your home.
- It passes through each hot-water radiator in turn and then returns to the boiler again.
- As the water flows through the radiators, it gives off some of its heat, warming each room in turn. The boiler has to keep firing in order to keep the water at a high enough temperature to heat a home.
- An electric pump is used to direct the water flow around the circuit of pipework and radiators.
- Some houses without a connection to the gas network will use liquid petroleum gas (LPG) or heating oil, which work in a similar way to gas but just more expensive to run.
What are the running costs of gas?
Gas boilers can provide significant savings. Some estimates suggest on up to £250 per annum when compared to other fuels such as oil, coal or LPG.
High efficiency condensing gas boilers may convert as much as 90 per cent of the fuel they consume into useful heat. Condensing gas boilers also produce considerably less carbon dioxide or CO2 than ordinary gas boilers as well as reducing the amount of heat that is lost from the flue.
Advantages of owning a gas system
Gas is a highly efficient fuel, which means you get a good return on every unit of energy. Unlike oil or LPG systems you don’t need to store any fuel with gas heating. Also, it is relatively simple to replace a standard gas boiler with a highly efficient modern condensing boiler.
Disadvantages of owning a gas system
Gas prices are continuing to rise and are likely to remain high. As a fossil fuel, gas produces carbon dioxide when burnt and is therefore not considered to be a clean source of energy. Gas boilers need servicing annually to ensure they run efficiently.
In addition to this, connecting your property to the gas network can be expensive if you are not already connected.
Electric central heating systems
An electric boiler can replace a small to medium sized gas boiler, and as the technology advances we are seeing electric boilers capable of meeting the demands of much larger homes.
They tend to need less components than their gas counterparts making them extremely light, small and compact, often completely silent and boast the main benefit of being 100% efficient. Electric is still a relative new-comer to the central heating market, and you would usually find them in rural areas where oil or gas supply isn’t as readily available.
However, we are now seeing some new housing projects or flats that are being fitted with electric boilers by choice due to its environmental benefits.
If you are considering a switch from gas to electric, be aware that the cost to convert your heating system may be considerable once you’ve factored in the new piping, boiler and installation costs.
If you currently have a gas system, our advice would be to stay with gas but consider replacing your boiler for a more modern, efficient one. Use our Comparison Tool to help you choose the right boiler for your needs.
Advantages of an electric central heating system
- If mains gas is not available in your area, electric central heating is an affordable alternative to storage heaters, oil, and even Lpg
- Can be run on a cheap rate electrical tariff
- Heat available on-demand where & when you need it
- Less service requirements than with gas powered systems
- Electric systems are 100% efficient
Is it cheaper to heat my home with gas or electric?
A gas fuelled central heating system will more than likely be cheaper in the long run.
Electric boilers are 100% efficient whereas a good modern gas boiler will see about 95% efficiency. As you might expect, some energy from gas boilers is lost through heat.
Even with the energy efficiency shortfall, electric boilers simply can’t compete with the cheap 4p / kWh cost of gas.
The 3 most popular central heating systems
There are a wide range of central heating systems available, and can be classified as follows:
- Combination or Combi boiler system
- Mains pressure or System boiler
- Conventional gravity fed or Regular system
Combi boiler system
The combination boiler central heating system is easily the most popular today.
These systems don’t require a feed tank, expansion tank or a hot water cylinder because they heat water as and when you need it. This means that they require a lot less space and are also economical – they only heat the water that you need.
- A combi boiler heats water on demand requiring no tanks within the loft space
- Electronic controls paired to your boiler
- Mains supply fed directly to the combi system
- Modern thermostatically controlled radiators sized accordingly
- Great for space saving
- Perform well with showers
- Endless amounts of hot water on demand
- Very economical – you only heat what you use
- No risk of loft pipework freezing
- Less need for pipework so installation in generally cheaper
As with the other systems, combination boiler systems also have their drawbacks. The main one is that their flow rates can be quite low as the water has to be heated as it travels through the boiler i.e. there is no stored hot water to fall back on.
This means they are unsuitable for homes with two or more bathrooms as the simultaneous use of two outlets will decrease the flow rate even further.
Combi boilers have two heat outputs:
- Hot water for your taps and shower
- Hot water for your central heating system and radiators
It takes more effort and therefore heat to get hot water to your taps and shower than it does to your radiators, so what you must consider when deciding on the right central heating system for your home is the hot water output your household will need.
Use our Comparison Tool to view the full range of combination boilers available and get installation quotes from local, trusted heating engineers.
Mains pressure heating systems
These systems supply mains pressure hot water through the taps in your home.
- Water is drawn in from the cold water mains and is heated by your boiler
- It is then stored in a storage tank (called an unvented cyclinder) until required
- When you open a tap in the house, cold water from the mains forces the heated water into the central heating system and out through the tap
The pressure at the tap of a high pressure heating system is the same as the pressure of the mains which in most cases is a lot higher than you would normally experience.
These particular central heating systems are great if you have a high mains pressure to start with but if the mains pressure is low then the system is unsuitable. They can also be costly to install and some authorities require a certificate of annual maintenance to be submitted to them.
You want to be 100% sure that your mains pressure and flow rate is strong enough to power a mains driven central heating system. If you go through the expense and hassle of having this type of heating system installed, but you get a trickle of water coming out of your shower – there is little you can do to rectify it at this point.
Regular / conventional boilers
These central heating systems use a boiler – either a regular boiler or a system boiler – to heat both the radiators and the hot water. The hot water circulates around the system and is then stored in a hot water cylinder until needed.
The water that travels into the boiler for heating often comes from a feed tank or expansion tank in the loft space of the house and it ensures that the volume of water in the system is always at its optimum level.
In addition to the feed tank, there is normally a larger tank present as well that replenishes the hot water cylinder when water is used around the household.
Water from this tank is drawn down into the system by the force of gravity alone – hence the name of the central heating system. The main drawback to this type of system is that you need loft space for the two tanks and an airing cupboard or similar space for the hot water cylinder.
These gravity based heating systems can work well, especially if you live in a low mains pressure area as the gravity aspect of this system can provide you with some decent water pressure if your mains pressure isn’t up to the job.
However, you will find that heating professionals tend not to recommend this type of central heating system anymore as there are quite a few negatives. For example, the need for two tanks in your loft and a cylinder in your airing cupboard can mean that installation costs will begin to creep up given the need for extra pipework and tanks.
If you do live in an older property that already has this Regular style central heating system, then it can be cheaper just to replace certain elements like the loft tank for example, rather than rip it all out and replace it with something else like a mains pressure system.
Wall Mounted Boilers
Most boilers produced today are made to be wall mounted, with more compact and lighter heat exchangers created with materials including lightweight cast iron, stainless steel, copper or aluminium.
Wall mounted boilers come in many versions, such as with a Fanned Flue or Room Sealed. As with most new boilers, the wall mounted type of boiler is required to have fitted a “system by-pass”, which is required to filter water throughout the boiler appliance to prevent the often loud noise that boilers are known to create, called “kettling”.
Free Standing Boilers
Usually created to be narrow enough to fit snugly between fitted kitchen units as other appliances would, these floor standing boilers can be installed in other suitable locations also. Free standing boilers were a popular choice in the 70’s and 80’s but are still a great option for homeowners who may not have the wall space for a wall mounted boiler now.
This type of boiler boasts an effective “heat exchanger”, which allows heat to be re-circulated rather than lost up the flue of the boiler, making it more energy efficient and therefore reducing fuel costs significantly for the owner.
One of the issues often mentioned with condensing boilers is the pluming effect it creates from the flue terminal, which is often mistaken for steam. The pluming is due to droplets of water that are held in suspension throughout the boilers flue, and is not a danger, although is considered a nuisance and will occur for all the time that the boiler is running. Because of this, the placement of a condensing boiler can be more difficult.