had a new combo boiler fitted 4 months ago but am still needing to constantly bleed the rads, mainly the upstairs ones, there dont appear to be any leaks in the system. should it take this long to get air out of the system or do i need to be looking at some other cause?
I too have this problem, I have to bleed the highest rad every other day, there are no leaks, someone told it was hydrogen gas so dont smoke when you let the air out.
If your system is a sealed system and you are still bleeding the rads. either there is a leak you haven't found yet or the burners are set to high on the boiler. This causes the water to evaporate like with a kettle. It will also make the boiler scale up which will cause problems later If this is the case you should get it looked at. Its not dangerous but it is a pain to have to keep bleeding the rads. Oh and the only thing coming out of a rad is air and water when you bleed it. If you are getting hydrogen coming out of the rads. I suggest you switch everything off and run.
I forgot to mentioned. If you look on the outside wall where your boiler is hung there should be a overflow pipe there. The loss of water could be going out there if the boiler is overheating. The system is sealed it has know where for the water to go except around the heating.
If this is a sealed system and lets assume that all the air has been expelled from the system. If the boiler was heating the water so much such that it boils, though this should be significantly reduced as the system is presurized, then the gas given off will be steam which may collect in the radiator. As this steam cools in the radiator then it should turn back to water leaving no 'gas'. So I would have thought that it would be air that is getting into the system somehow. Can sealed systems experience negative pressure that would allow air to enter the system? Maybe their boiler is designed to heat the water using 2 electrodes arcing in the water
many thanks to you all for your advise, i'll get the burner temperature checked out, and hope it is just air coming out the rads, cheers all