Open Vented Central Heating System Diagram

Central heating systems are either open vented or sealed systems.

Open vented central heating system diagram.

There is also a vent line that releases any air in the system and returns any water or steam to the top of the expansion tank in the event of. Nb not to be confused with vented and unvented hot water tanks which are explained in our guide to hot water cylinders many homes in the uk still have an open vented heating system and in some cases they are the better option for your home. No external pump no tanks no external expansion vessel no motorised valves and in many cases item 6 is not needed either. The diagrams below show three central heating types.

Draining an open vented central heating system is fairly straightforward. An automatic bypass valve is fitted inside most combi boilers by the manufacturer these days. Open vented system using a hot water cylinder a sealed system using a hot water cylinder and combination boiler systems. The vented boiler regular boiler and combination boiler systems probably account for over 95 of water based central heating installations.

You will find a draincock usually situated on the return pipe blue in our diagram which is used to drain the water from the system. You will need a rubber hose long enough to reach an outside drain from the draincock. Open vented central heating system. Fitting the components together to make central heating systems central heating systems come in generally three combinations.

The open vented system is fed from a feed and expansion tank located in the loft this keeps the system topped up and also allows the water to expand as it heats up.