Radiators are heat emitters, which provide the heat to the various rooms. Radiator proficiency has changed over the years from cast iron heavy radiators to pressed steel. These add in fins to increase the surface area a give a higher output of heat. Aluminium radiators have also been popular giving the opportunity to create special effects in an up to date environment.
If air is trapped in the system you will be aware that the top of the radiator is cool if the lower half of the radiator is hot. Use a radiator-bleeding key to unlock the air vent at one end of the top of the radiator. Make sure you have a piece of rag ready to collect the water once it starts to flow. Do not open the vent entirely. One turn is usually enough to hear the hissing of the escaping air. Once water starts to emerge at the vent, close it up. The water can be very warm, so it is safer to turn the heating off whilst you complete this job.
If you find that radiators, or a particular radiator needs bleeding on a regular basis, then air is entering the system. This predicament can cause corrosion and there may be a problem with the system that needs expert assistance. It could be caused by a build up of sludge in the bottom of the radiator, inhibiting the motion of water. There is a sludge removal liquid available. Add the liquid to the feed and expansion cistern. A few days later, depending on time required it will be necessary to drain and replenish the system.
If the airlocks are more severe, it could be due to lack of water in the system, leaks or a design fault somewhere in the pipework. Bleeding the radiators doesn't help if the problem is more serious. Establish where the pump is and find the flow regulator. Make a note of the setting, before using a screwdriver to turn it off and on very quickly for a few times. If this is still unproductive, try bleeding the pump itself. The bleed valve should be evident on the top of the pump casing. Open and close it with a screwdriver very quickly. If you hear the sound of air hissing - you have located your problem.
All the radiators are cool This problem is probably due to a build up of sludge within the system. The sludge - black iron oxide, is caused by corrosion on the inside of the pipes and radiators, ensuing in poor movement of water. The system needs to be thoroughly cleaned with a special chemical. There is a sludge removal liquid available. Add the fluid to the feed and expansion cistern. A few days, later depending on requirements it will be required to drain and refill the system.
If Lower radiators are cool and upstairs radiators hot It is most likely due to the pump deteriorating. Turn the central heating system off, wait for the pump to cool and try to start the pump manually. In the middle of the pump, remove the screw and turn the pump's manual starter - the impeller.
No luck? Try tapping the pump two or three times with a mallet, gently but sharply.
No luck? Try removing the pump and use a hosepipe to flush it through with clean water. The pump should not be submerged in water.
No luck? Remove and renew the pump.
Cool radiators which are the farthest away from the boiler – you will need to check the complete system, as it is not correctly balanced.
Upstairs radiators are cool, lower radiators hot if the heating is working downstairs but is cool upstairs this often indicates that the feed-and-expansion cistern is empty. Refill the cistern allowing just enough water to float the ball when the water in the system is cold. The extra space is needed to house the expansion of the water as it is heated up. Another problem could be a defective ball valve.
Upstairs radiators cool, except when hot water only is selected on the programmer If the system is gravity driven, hot water from the hot water cylinder fails to reach the upstairs radiators when a gravity-check valve switches off the heating. When the heating is switched on, hot water will rise naturally above cooler water. The gravity-check valve can be found on the flow pipe to the upstairs radiators. If it is stuck in the 'open' position, the pipe on either side of the valve will be warm. It needs replacing and it might be time to call in a central heating engineer.
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