Gas boilers use natural gas to produce the heat that is then used to heat water or other fluids in a pipe that passes close to the heat produced. They are usually very efficient especially the condensing boiler where the exhaust gases pass out through a heat exchanger that warms cold water returning from radiators thus helping to heat it up and reducing the boiler’s work.

Below is a diagram illustrating the processes involved in a gas boiler system.

1 - Natural gas entering, 2 - gasaes burning in boiler, 3 - pump for pumping the heated water, 4 - shows the areas the hot water/vapor may move through, 5 - its possible for the water to move to higher heights, 6 - thermostat.

Natural gas enters the system through a pipe and is directed to the boiler. The boiler burns the gas producing the heat required to heat the copper pipe containing water. The copper pipe (heat exchanger) has several bend so as to increase the area exposed to heat thus maximizing the heating effect. An electric pump is used to push the heated water so that it can flow to all required areas. The pump should be powerful enough to push the water to all the heights it is required to go to. The water then moves round doing the intended work e.g. warming the house and since it loses heat, it return to the boiler for heating before continuing with the cycle. A thermostat is mounted within the system somewhere to monitors the temperature and switch the boiler off when temperatures are above the required and switching the boiler back on again when the temperature fall below the minimum level. During combustion there are waste gases from the boiler that leave through a small smokestack called a flue and disperse in the air.

Below are some steps to carry out during the troubleshooting and repair of modern boilers without a pilot flame burning continuously that is gas fired:

1)The thermostats should be checked to ensure that they are set above the room temperature or the desired temperature. For the analog boilers ensure the thermostats are level and if damaged beyond repair they should be replaced.

2)Ensure that the circular pump is running correctly. This is done by feeling the motor. A cold motor means the pump is not running which can result from a faulty breaker that supplies power to the boiler. A very hot motor indicates a problem with the run capacitor.

However if the motor is cool the problem is on the thermostat.

3)Make sure that the temperature and pressure gauges are above zero reading and below the red/maximum reading. Too low temperatures indicate a problem with aquastat or boiler control.

4)The vent dumper should be open and the inducer fan running. If not so there is a problem with the pilot (the pilot vent could be blocked, dirty flame sensor, bad boiler control or a faulty thermocouple).