When some of the radiators used for a central heating system in your home are hot and others are cold, they will need to be balanced to provide an even amount of heat. A radiator has coils that are heated by hot water that comes from a boiler to provide radiant heat for each room. You can balance a central heating system radiator by regulating the temperature between two of the valves on the radiator.
Bleed all of the radiators with the radiator bleeding key. Bleeding will remove all of the excess air that is in the system. Turn off the heating system to allow the radiators to cool down.
Find the lockshield valve on the radiator. The lockshield valve has a push-on cap or a cap that is secured with a screw. Pull off the cap or remove the screw with the screwdriver.
Find the wheelhead or thermostatic valve on the other side of the radiator. This valve will have a knob and is used to turn the radiator on and off.
Place the lockshield valve adjuster onto the lockshield valve and turn it counterclockwise or to the left to open the valve. Go to the other side of the radiator and turn the wheelhead or thermostatic valve counterclockwise or to the left to open the valve. Repeat this step on all of the radiators.
Turn on the heating system and note on a piece of paper the order in which the radiators in the home heat up. The first radiator to heat up will be the one closest to the boiler. Turn the heating system back off and wait for the radiators to cool.
Turn the heating system back on and then go to the first radiator that you noted in Step 5. Close the lockshield valve by turning it clockwise. Open the valve by turning it a quarter of a turn. Take a temperature reading, at the valve, with the digital thermometer after the radiator has been heated.
Get a temperature reading on the wheelhead or thermostatic valve. Open the valve slowly and note the temperature reading on the thermometer. Stop opening the valve when there is a 20 degree difference between the current temperature and the temperature you noted in Step 6.
Go to the next radiator that you noted in Step 5. Repeat Steps 6 and 7 to balance each remaining radiator in your home.
The lockshield valve will need additional turns to open it the further away you are from the boiler.