Presentation on Feed and Expansion Cistern

Central Heating At the end of this part you should be able to: Identify general system methods of feed and vent Explain the purpose and function of the component parts Know how to set the water level correctly in the F&E cistern

System components Now we’ll look at some of the key components within the pipework system. This will include the: Feed and expansion cistern Primary open safety vent Central Heating

The feed and expansion cistern is used on all open vented system.. what do you think it’s for ? The cistern allows the system to be filled up. Main purpose is to allow water in the system to expand. Water level should be set low in the cistern when filling the system. Feed from the system on an average domestic property is usually 15mm and should NOT include ANY valves … why ? This to ensure that in the event of overheating there is a constant supply of cooler water to the system to prevent the dangerous condition of boiling occurring.  Central Heating – Feed and Expansion

Water level in F&E below cistern Open vent to rise min 450mm above cistern to prevent surge effects The f & e cistern is located at the highest point in the system, and it must not be affected by the position and head of the circulating pump. To avoid any problems on gravity primaries a minimum height can be obtained by dividing the maximum head developed by the pump by 3 On fully pumped systems, the level of water in the f & e cistern should be a minimum of 1m above the pumped primary to the DHW storage cylinder. Allow 4% of system volume for expansion Central Heating – Feed and Expansion

Flow to cylinder Return from cylinder Flow to heating Return from heating Cold feed from F&E 15mm Open vent to F&E 22mm Both of these pipes tee into the primary flow from the boiler BEFORE the pump IN THE ORDER shown Central Heating – Fully pumped cold feed and open vent position