Central Heating Problems

Radiators cold along the top

A common reason radiators are cold along the top is due to air being within the top of the radiator.

This air must be bled from the radiator so the central heating water can take it place.

To bleed the radiators

Tools required - Radiator bleed key and an absorbent cloth

First of all it is useful to know if your central heating system is pressurised or gravity fed.

If it is pressurised you should be able to locate a mechanical pressure gauge on the front of your boiler or on the pipe-work near to your boiler.

There will also be a 'Filling loop'. The filling loop is connected from the mains cold into the central heating system and shut off with either one valve or a valve at either end. Ensure the pressure within the central heating system is 1.5bar.

NOTE: DO NOT OVER PRESSURISE YOUR BOILER. IF THE PRESSURE GOES ABOVE 3bar A SAFETY DEVICE CALLED THE PRESSURE RELIEF VALVE WILL OPEN AND THE CENTRAL HEATING WATER WILL FLOW OUT OF IT. Providing it has been installed correctly this will dump the central heating water outside. Furthermore, the pressure relief valves don't always reseat and you'll need to call us to replace it. Be warned!

If it is not pressurised and gravity fed from a tank, often in the loft as you bleed air from the radiators water will normally gravity feed its way into the central heating system without you having to do anything.

Using a radiator bleed key, open the bleed nipple on a down stairs radiator until all the air is forced out and water starts to spur out of the nipple. Then, carefully catch the water with the cloth and tighten the bleed nipple immediately.

Go back to the boilers pressure gauge, and using the filling loop top the pressure back up to 1.5 bar if necessary.

Repeat this until all the radiators have been bled.

If the problem still persists it will need investigating with a view to power flushing your system or replacing the radiator.