|
 General Information
Water based central heating systems only work well if there is minimal air in the system. Air in the system can cause radiators to not get hot at all or radiators are cold over the top part of their radiating area. These effects reduce the efficiency of the central heating system and can lead to increased costs. Getting all the air out of the central heating system needs to be done before trying to balance or set up the system. Bleeding radiators should only be necessary annually or after modifications and repairs to the system.
What Does Bleeding The Radiator Mean?
Bleeding a radiator means opening a small valve to allow any trapped air to be expelled.
Does A Radiator Need Bleeding?
If a radiator is cold and used to work the problem could be due to air in the system. In this case it is best to bleed all the radiators and any other bleed valves you can find, often there are two in the loft. If the radiator gets hot at the bottom and not at the top then the radiator probably needs bleeding. Air in the system can also cause a knocking noise in the pipes when the heating is running and bleeding all the radiators will often solve it. The knocking noise is caused by air trapped in the pipes.
 How To Bleed A Radiator
Most radiators have a small bleed valve at one end at the top (double radiators may have two bleed valves), usually these require a square or hexagonal key or a screwdriver to open them.
 Air is expelled either through a small hole adjacent to the bleed valve or more usually around the thread of the bleed valve itself. Radiators are often painted which means that the bleed valve is clogged with paint and difficult to open. Sometimes the bleed valves are damaged and cannot be opened using the proper key, in this case an adjustable spanner or a small socket may do the job. When all the radiators are being bled it is sometimes necessary to go round them all more than once. Success is when each radiator has a uniform temperature over the whole of it's surface area.
Before starting make sure you have the correct tool to open the valve, plenty of rag and a small container to catch any water expelled.
1. Run the heating system until it has reached normal temperature and then turn it off.
2. If a thermostatic valve is fitted open it fully but remember where it was set to enable it to be reset afterwards.
3. Wrap a rag loosely around the bleed valve.
 4. Open the bleed valve a small amount anticlockwise until air starts escaping (usually a hissing sound is heard) , leave the valve open until water starts coming out. This can take a while especially if there is not much pressure in the system. Be careful as water can spray out suddenly. Once all the air is out close the valve.
5. Rest the thermostatic valve if fitted.
6. On pressurised systems adjust the system pressure back to normal following the manufacturers instructions.
7. Check that the bleed valve is not leaking.
|
