Gas Boilers are central heating systems that use different types of fuels to burn – most commonly natural gas (on a grid) or bulk oil, LPG stored on site. This fuel is then burned in the boiler’s combustion chamber, normally by the burner fitted onto the boiler. The heat then warms the water in the heat exchanger to around 70°C domestic (industrial and commercial boilers operate at a higher temperature). This heated water is then pumped around the property through pipes and radiators in order to heat space, and can also be pumped directly to taps or showers.
Types of Industrial and Commercial Boilers
There are two general types of boilers: fire-tube and water-tube. Boilers are classified as high-pressure or low-pressure and as steam boilers or hot water boilers. Boilers that operate higher than 15psig are called high-pressure boilers.
A hot water boiler, strictly speaking, is not a boiler. Technically, it’s a fuel-fired hot water heater. It is because of its many similarities to a steam boiler that the term ‘hot water boiler is used.
Single-pass fire tube
These boilers are likely to be found in older establishments, dry cleaners or in factories where clothes are manufactured. Typically they are used for creating the steam required for ironing processes. Single-pass fire tube hot water boilers can be found in many other buildings such as schools, office buildings, hospitals, universities, libraries, and other similar facilities.
They represent older boiler types with a single set of fire tubes, whereby the burner fires into the tubes at one end and gas combustion products exhaust to the flue at the other end. Because there is only one pass of combustion products, the heat transfer to water is not very efficient, efficiencies are likely to be down around 60% (or less).
The boiler will be either vertically or horizontally mounted. On the smaller vertical boilers, the burner system is likely to be natural draught, whilst the larger horizontal boilers will be fired by fanned draught.
Multi-pass fire tube
As the need for higher efficiency boilers grew, so the multi pass system was developed to allow more convective heat transfer surface area. By installing more tubes and creating a system whereby the flow of the combustion gases passes through a second, third and even fourth pass of the tube configuration a better heat transfer and efficiency of the boiler.
The name ‘fire-tube’ says it all: the fire, or hot flue gases from the burner is channeled through tubes that are surrounded by the fluid to be heated. The body of the boiler is the pressure vessel and contains the fluid. In most cases, this fluid is water that will be circulated for heating purposes or converting to steam for process use. These boilers are also found in office buildings, universities, hospitals, schools, and other similar facilities.
Essentially, condensing boilers are water heaters fuelled by oil or gas. These appliances can achieve exceptionally high level of thermal efficiency up to 98%. This high level of efficiency is achieved through the condensing of water vapour which takes place in the heat exchanger and exhaust gases.
With the condensing design, The boiler recovers a good portion of the heat of vaporisation, which would otherwise be wasted. Most models boast efficiencies over 90% when correctly fitted, and when used, the temperature of the return water is at or below 43°C. As the temperature of the return water decreases, the boilers efficiency will increase.
Absence of an effective maintenance regime can lead to a significant drop in a boilers efficiency or could even lead to a breakdown. It is recommended that you service your boiler a minimum of once a year.
Importantly, when natural gas is burned without enough oxygen it burns yellow. This creates a dangerous toxic gas called carbon monoxide, which can be lethal if inhaled for long periods. However, providing you a have a functioning carbon monoxide detector and a regularly serviced boiler, you shouldn’t have any problems at all.