Knowing All the Different Central Heating Parts

There are a number of important central heating parts that make up the entirety of your home heat system. These main parts all serve a specific function to enable smooth operation.

Feed and Expansion Cistern

This is a vital component of your central heating parts, as it allows the water under pressure to move up and down. This allows back pressure in the system to push air out of the lines naturally and at the end of the water return cycle. The water comes from the system hot and overflows from pressure into this section to separate steam, trapped air, and mix fresh water into the line. From here it is pulled from the bottom of the cistern by the circulation pump towards the boiler.

Circulation Pump

This is responsible for assisting fresh water getting fed into the boiler and throughout the system. At this junction the water has been cooled and separated from trapped air gases by the cistern. The water does not feel the heat pressure at this point in the journey and a pump is needed to move the water through the central heating parts to the boiler.


The core heating element in your central heating is this cast iron monster, generally fueled by oil or coal. It takes water through the cast iron walls around the central fire chamber, where the water heats and becomes pressurized through evaporation into the outlets of the chamber to the radiators and heating coil.

Zone Valves

This is found in the lines running throughout your central heating parts to help bleed the lines by adding or removing water back pressure. The lines can be completely closed as well so that you can shut off the heater tank and still have the boiler heating the house, or even the other way around. This allows more control over your water system, and for quicker maintenance without having to shut down your boiler or having to wait for it to cool off.

Hot Water Storage Cylinder and Coil

Your central heating parts also can effect other areas of your home other than just the heating of air. Some systems have a secondary tank, called a water storage cylinder, that has a coil running through it from the boiler itself. This coil is heated by the boiler and runs through the water drum in a coil to help cool the water before it is returned to the cistern, as well as heat the container of water on the way. The water in the tank is then under heat pressure from the heat exchange of the coil and can be run throughout the home as hot water lines.


The boiler water under this pressure also sends heated water through the central heating parts to the radiators, which are commonly known as those old cast iron stand-ups that burned when you touched them. The cast iron structures of the old radiators have been replaced with steel and aluminum radiation units that look more like conventional heating ducts, mounted only at the baseboard level of the walls. The hot water pushes the old water out through the ends of the radiation unit to the cistern for recycling.