How Do Gas Boilers & Furnaces Work

In the olden days, heating a house was a difficult task. Oftentimes, the upper class would have a fireplacenatural gas boilerroaring in every room in their house. The less fortunate would sleep with heated bricks at the foot of their bed, and do their best to stay warm with clothing and heavy blankets.

The idea of using a central heat source to control the warmth of the rooms in a house or building was met with great enthusiasm, and today central heating and even central cooling systems are commonplace and popular.

Gas boilers
heat water that moves in specialised tubing from room to room, heating the radiators throughout the structure. These versions of heating systems are extremely convenient and help to stave off the cold during winter months. They offer an economical way to stay comfortable in all the rooms in a building while keeping heating costs and upkeep costs relatively low.

 What does a boiler do?

The boiler is the primary source of heat in a gas heating system. A gas boiler is supplied fuel by a pipeline in a building that is connected to a bigger pipeline underground. An electric switch powers on the boiler, which turns the gas fuel into heat through a series of combustion chambers. The heat that is generated through the combustion chambers is then carried on to the water in the system.

Water Heating & Circulation

The water in the system heats up considerably, to about 60 degrees Celsius. Then the heated water is ran through a massive structure of piping that runs throughout the building. As the water circulates through the pipes, it reaches the radiators to warms the building and then it returns to the boiler to be reheated.

The heat is transferred to the individual radiators throughout the building as the water circulates through the pipes and returns to the boiler to be reheated. 

The electric switch on the boiler helps not only to turn the machine on, but to assist in pumping the heated water through the system. Pumping the hot water out into the pipes and radiators helps to ensure the cooled water returns to be heated.

What do thermostats do?      

boiler thermostatThermostats are found in most homes with a central heating system. Oftentimes, space heaters also have thermostats. Thermostats are like thermometers in that they gauge the temperature of a room or space. They also contain a switch that will stop heating or start heating to maintain whichever temperature the user has set the thermostat to.

Thermostats are a convenient way to maintain a certain room temperature without having to keep a heater constantly on, or have to manually switch the heating apparatus on or off. Some households have heating programs that are set on electronic timers. These timers will turn the boilers on or off at predetermined times, such as bedtime or when the house will be empty. These hourly timers are an alternative to temperature controlled thermostats.

 How do radiators work?               

how do radiators workRadiators are not to be confused with space heaters. Space heaters, as previously mentioned, are electronically controlled and oftentimes come equipped with a thermostat, or temperature control switch, whereas radiators are simply a length of pipe filled with warm water from the boiler. The pipe is classically accordion style, folded back and forth a number of times.

This is done to create a large, dense surface area to release heat into the room in a more uniform way. The radiator does not have thermostat abilities. The temperature of the water that is heated by the boiler is controlled by the boiler itself, and radiators are simply a way to transmit the heat from the water into the air of various rooms.

Screw Valves – How to switch on and off the radiator

Each basic radiator has a screw valve found near the bottom of the radiator. This valve serves to be the on and off switch of the radiator. Each individual radiator can be switched on and off throughout the building. If you were to turn the screw up on the radiator, you would turn the radiator on.

Turning the radiator on means that you are now allowing heated water from the boiler to flow through the pipes. If you were to turn the screw on the radiator down, you would turn the radiator off. The radiator would then empty of water as the valve closes and the hot water begins to entirely bypass the radiator and continue on its basic circuit back to the boiler.

How do thermostatic radiator valves work?

thermostatic-radiator-valveThough radiators typically come standard with no built in thermostat of their own, only an on and off switch, there are valves that can help to offer users a bit of a temperature control in various rooms. Thermostatic valves are valves that can be used with radiators in an effort to offer more control to users in terms of the temperature in specific rooms throughout a boiler system. These thermostatic radiator valves also lend a hand in saving energy and money. As opposed to having all the rooms throughout a system strive to reach the same temperature, a user can focus on more trafficked areas and save energy by focusing heat into necessary areas.

The Role of  Radiator Valves in Heat Circulation

Firing up the boiler in a house means that the water in the system begins to heat and circulate that heat. The circulated heat has a base temperature set by the user. The base temperature of the water determines the heat output of the radiator, and the same temperature is generated by each radiator. The maximum heat will kick in for all radiators in the on position.

As the heat from the water reaches the base temperature, the valves start to turn off so the boiler fires less frequently. This will reduce the temperature of the water inside the radiator and cool it to a lower heat. Eventually, the heat will reduce until the room temperature has cooled too much. At this point, the thermostatic radiator valves reopen, and the heated water is again pumped into the radiator.

Radiator Valves & Room Thermostats

Radiator valves are an excellent tool when paired with a thermostat, or even on their own as a way to streamline temperatures throughout a system. Technicians do not recommend that users use these valves in a room with a main wall thermostat. The wall thermostat will attempt to exert temperature control using the boiler, and can influence the temperature of the radiator.

The radiator valve can work against the thermostat as well, preventing a room from reaching a desired temperature or keeping a room at a temperature higher than the thermostat is set to. Also, in a setting with rooms that can be affected by the room temperature in neighbouring areas, Gas boiler users are recommended to shut the door to help each room maintain its set temperature. Rooms that have cooler air could influence a room with a higher temperature setting, and cause the room’s radiator to work overtime in a effort to heat the additional air.

How do boilers make hot water?

Oil boiler tune upBoilers make hot water in a few different ways. The heating of the water varies based on the type of gas boiler owned. Most gas boilers on the market today offer purchasers the luxury of doubling as a hot water heater. Two of the most popular types of gas boilers are open-vented boilers, the kind that heat water from a tank, and combi boilers, gas boilers that heat water on demand.

To explain further the inner workings of a combo boiler, imagine that the hot water tap is turned on. This running of the tap is essentially the opening of a valve that water then comes through from the boiler. If a combi boiler is doubling as a hot water heater, the gas boiler will turn on and heat the water. A central heating boiler often stops heating the central heating water when its other valves are open. The central heating boiler, or open-vented boiler, does not have enough heat energy to warm both reservoirs at once.

What are condensing boilers?

how-do-condensing-boiler-workGas boilers work through the science of combustion, which means that they burn fuel from an outside pipeline in combination with oxygen to yield carbon dioxide and steam. The carbon dioxide and the steam that is formed tend to escape from a type of boiler chimney called a flue. In addition to the escape of the steam and carbon dioxide, the heat of both escapes as well. The loss of this heat is in turn a loss of energy, which equates to a dip in the productivity and efficiency of the machine. In an effort to maximize the productivity of agas boiler, inventors introduced consumers to the condensing boiler.

With a condensing boiler, the flue transmits the carbon dioxide and steam through a device called a heat exchanger. The heat exchanger takes in the carbon dioxide and steam and warms the cold water that is returning to the boiler from the radiators. By using this heated run off of gases, the water gets heated significantly without using any power from the boiler first. Though condensing boilers are more expensive and require a more detailed maintenance checklist, they are wonderful in terms of maximizing energy efficiency. In fact, over 90 percent of the gases’ heat energy is carried over into the water that heats the radiators.

Can you run a boiler on fuels other than gas?

There are several different types of boilers available for purchase by consumers. Some options include the gas boiler, which has been discussed in some detail in this article, a wood or coal burning boiler, and an oil boiler. When considering a boiler system, differentiate between the radiator’s role in a building and the role of a boiler. Boilers and radiators are separate entities, and one can be replaced without replacing the other, though replacing radiators and a radiator system is understandably more difficult than replacing the boiler.

Do you always need a pump?

Essentially, yes. Most modern boiler systems use a system that is called fully pumped. Using this system means that the boiler’s water is circulated using an electronic pump that circulates the heated water throughout the heating system. An older method of circulating the boiler’s water into radiators was called the gravity-fed system. This pumping design relied on gravity and the convection of water to assist the flow of the heated liquid into different areas. A hybrid of these two systems is known as a semi-pumped system.

Safety Considerations

Maintaining a properly functioning machine is crucial in the ownership of a gas boiler. Ensuring that the gauges are all reading properly, the machine is tuned and has all the necessary parts, and employing a professional to come examine the machine at least annually are all important safety considerations. The main cause of injury or incident involving gas boilers are related to the ignition of a combustible gas within the device. For this reason, proper maintenance and ventilation are crucial to the preservation of the boiler.

Best Maintenance Practices

One of the most important parts of maintaining a boiler would be to remain efficient in practice. Checking your boiler’s gauges against the recommended standards in the owner’s manual helps ensure that your energy efficiency is as high as possible. Ensuring a proper combustion is occurring through the use of your boiler is essential in avoiding complications in terms of dangerous gases or pressures building. Optimizing controls, being familiar with your equipment, and maintaining contact with a professional in the event of any questions or concerns are all great ways to maintain a gas boiler.

Keeping a boiler clean, and using boiler maintenance checklists are also important in assisting a user in practicing the best maintenance practices. Preventative maintenance, careful monitoring, and daily records are instrumental in staying ahead of the curve on the health of your boiler as well.


In conclusion, gas boilers work through an ignition switch that burns a natural gas against oxygen and harvests the energy into heated water. This heated water is circulated through the house using a radiator system, and the rooms in a building may use a thermostat in an attempt to maintain a respective temperature in a room.

Individual radiators throughout a system may house radiator valves, offering that room an option as to how to control the temperature in the space. Gas boilers are an efficient way to have central heating in a space, and though boilers can generate heat using different methods, gas boilers are popular due to the ease of access that many have to natural gas pipelines. With proper maintenance and care, boilers are a safe and energy efficient means to central heating.