When bleeding central heating there are a few factors to take into account, such as the source of the problem and whether the problem is in your system itself or in the radiator. When you add new water to the system it allows air to enter as well. At the core of this line is a pump that also generates a certain amount of air in the lines as it runs. Because air rises and is lighter than water, it will float to the top of your radiator or water system itself running the internal flow of the unit.
You would be bleeding central heating lines when you have determined there is a loss of water pressure in the lines of your unit. The most common cause of this is air getting trapped in the radiator lines causing a loss in the heat being pushed out of the blower. You will need to turn on your heating unit and check with your hand the temperature of air on the bottom and the top of the unit, if the bottom is hotter than the top, this is likely the issue.
Bleeding the Radiator
When you start bleeding central heating turn the pump and the unit off to prevent the air pump from pushing more air into the system while you operate. Bleeding the radiator on a sealed system can very well affect the system’s internal pressure and have to be readjusted after you are done.
The next step, once the unit is off, is to make sure the cold water intake is attached and on to help put back pressure on the radiator which will help to push the air pockets out as you progress. Take your valve key and turn the valve on your radiator until you hear a hissing from the trapped air escaping. Be cautious if you have just recently turned the unit off that the water coming out could be hot, and you may want to use a large cloth to turn the key to avoid scalding.
Once water begins to leak from the valve, go ahead and shut it with the same method. Be sure to clean up any water that may drip down to avoid mold growing in the unit. Bleeding central heating can clear air from your lines making your radiator more efficient in your unit, as little things such as this can have a huge impact on cost efficiency of a central heating system.
Bleeding the Circulation System
Another problem in bleeding central heating is checking the circulation system itself. You simply turn off the heater and locate the release valve for the circulation system itself. Twist the valve with a loose cloth and wait for water to come through and the hissing to stop. Again clean up any drippings to avoid mold growth. Tighten the valve once it disperses water instead of air.
You can avoid issues in the future and avoid bleeding central heating lines by doing this in the process when you refill the lines to begin with. Bleeding the lines should be the very next step when changing or checking the water levels in your radiator and water circulation system.