Central Heating

[naseem]

My central heating works fine but my hot water will not heat up. If I release the air from the sysytem via a air vent near the boiler both the inlet and the outlet to the cylinder get hot then go cold until I release the air again. Please could you help me?

[KARL]

This is not an easy question to answer because more information is needed to give a better indication of your essential problem. It seems clear that there is an airlock forming in the system whereby circulation to the cylinder stops. Whether this is a large "bubble" somewhere that is being moved bit by bit to the vent location or whether there is a fundamental design problem is unclear. I suggest you set the pump to its lowest speed and keep venting the air until you (hopefully) get sustained circulation. If this setting does not give you adequate circulation at no-air-buildup, then try the next up and see if air build up as quickly again.