To choose the right heating system for your home, start with the boiler type that fits how your household uses hot water and the space you have: a combi, a system boiler or a regular boiler, with radiators and controls to suit. A replacement gas boiler will probably have to be a condensing boiler, and anyone paid to work on it must be a Gas Safe registered engineer. Climate Flow Limited services and repairs domestic gas boilers, radiators and pipework across London and surrounding areas, and is Gas Safe registered for domestic gas work.
How to choose the right heating system for your home: the three boiler types
There are three main boiler types. They differ in where the hot water comes from and in what else has to fit in the house.
Combi boiler
A combi (combination) boiler heats the radiators and heats water straight from the mains when a hot tap is turned on, so there is no hot water cylinder and no cold water tank in the loft. Of the three types, it needs the least room. The water is heated as it is drawn, so the flow at the tap depends on the mains supply coming into the house and on how many taps are running at once.
System boiler
A system boiler heats the radiators and a separate hot water cylinder, usually kept in an airing cupboard. It is fed from the mains, so there is no tank in the loft, but the cylinder needs its own space. Because the hot water is stored, more than one tap or shower can draw from the cylinder at the same time. Once the stored water is used, the cylinder has to heat up again.
Regular boiler
A regular boiler is also called a heat-only or conventional boiler. It works with a hot water cylinder and a cold water storage tank, usually in the loft, that feeds the system. You often find one in an older home that was built around a tank and cylinder. Keeping a regular boiler can mean fewer changes to the existing pipework.
Which boiler type suits which home?
The right boiler type for a home is the one that matches its hot water demand, its water supply and its space. No single type suits every home. These are the questions an engineer works through with you:
- How much hot water is used at once. If the household often runs two showers together, stored hot water from a cylinder is worth considering.
- The mains supply. A combi and a system boiler both depend on the water coming in from the street. If that supply is weak, you notice it at the tap.
- Space. A combi needs room for the boiler only. A system boiler also needs a cylinder. A regular boiler needs a cylinder and a loft tank.
- What is there now. Changing from one type to another means changing pipework, and sometimes removing or adding a cylinder or tank, so the existing layout matters.
- Where the boiler and its flue can go. The flue is the pipe that carries the combustion gases outside. Where the boiler can sit depends on where the flue can safely run.
What rules apply to a new gas boiler?
The first rule is about who does the work. The Health and Safety Executive states that anyone employed to work on gas appliances in domestic premises must be a Gas Safe registered engineer. That covers fitting, servicing and repairing a boiler.
The second rule is about the type of boiler. The Planning Portal's Building Regulations guidance on boilers and heating says that a replacement gas boiler will probably have to be a condensing boiler, unless there is good reason why one cannot be fitted.
In England, the government's Boiler Plus factsheet states that all gas boilers installed into existing systems must have an ErP efficiency, the boiler's rated efficiency, of at least 92%. When a gas combi boiler is installed in a home in England, the factsheet says an additional energy efficiency measure is mandatory, and it lists the measures that qualify. Both are minimum standards for the installation. Neither tells you what a particular boiler will cost to run in your home.
Once the boiler is fitted, the Planning Portal says the installer should give you a commissioning certificate, such as a Benchmark certificate. Keep it with the boiler's other paperwork for future servicing.
How do radiators and controls fit in?
The boiler heats the water, and the radiators and controls decide where that heat goes and when. Radiators pass heat from the circulating water into each room. The pipework between them is part of the system an engineer checks when a boiler is changed or when a room stays cold.
- Room thermostat. Switches the heating on and off to hold the temperature you set in the room where the thermostat sits.
- Programmer or timer. Sets the times the heating comes on, and the hot water too on a system with a cylinder.
- Thermostatic radiator valves (TRVs). A TRV is a valve on a radiator that controls the flow of hot water through that radiator to hold the room at its setting.
- Cylinder thermostat. On a system or regular boiler, holds the stored hot water at its set temperature.
One room that never warms up, a radiator that is cold in patches, or noisy pipework can each come from the radiators or pipework rather than the boiler. Have them looked at before you decide the boiler is the problem. Climate Flow's work on domestic central heating and boilers covers radiators and pipework as well as the boiler itself.
What else to weigh when you choose the right heating system for your home
Every boiler type has to be looked after. HSE advises that all gas appliances, flues and pipework should be regularly maintained and serviced at least annually. HSE also strongly recommends carbon monoxide alarms as one useful precaution to give advance warning of carbon monoxide. An alarm is an extra safeguard. It does not replace a service.
Before an engineer works on your boiler, ask to see their card. HSE's domestic gas safety guidance explains that all Gas Safe registered engineers carry ID cards that tell you which appliances they are qualified to work on.
Climate Flow services and repairs domestic gas boilers and works on radiators and pipework across London and surrounding areas. Climate Flow's full list of services also covers commercial refrigeration and air conditioning.
When to call an engineer
Call a Gas Safe registered engineer if a gas appliance shows signs that it is not burning properly. HSE lists these signs:
- yellow or orange flames rather than blue ones;
- soot or brown staining on or around the appliance;
- more condensation than usual on the inside of windows.
Do not try to find or fix the fault yourself. HSE says that every year around 7 people die from gas-related carbon monoxide poisoning.
If you smell gas, follow the National Gas Emergency Service's advice. Call the National Gas Emergency Service on 0800 111 999, open doors and windows, do not use electrical switches or naked flames, and turn the gas off at the meter unless the meter is in a cellar. Call them before anyone else.
If your boiler has broken down and there is no smell of gas, Climate Flow offers 24/7 emergency callouts on 020 3488 5452.
This guide is general information, not a survey or a quote for your site; every system is different, so an engineer needs to see yours before any work is priced.