No CH circuit vent pipe on fully pumped system

[bfob]

Have a bit of a problem in a house I moved recently.

The central heating looks as though it has been converted from a gravity fed hot water system to a fully pumped system. However, the vent pipe to the expansion tank comes off the hot water circuit and the cold water feed also goes to the hot water circuit.

There is often a metallic bang when the heating kicks in. I an guessing that this is air in the circuit and have bled the rads a number of times but this has not elliminated the noise

Questions

a) Does the heating circuit need a vent pipe

b) Because the boiller has been positioned in the garage it will be impossible to have a completley vertical run to the expansion tank. There will need to be some horizontal sections. Is this OK?

c) Do I also need to run the cold feed in the the CH circuit?

d) Would an automatic air separator device positioned between the boiler and pump be an acceptable alternative to a vent pipe to the CH circuit? (The pipe mods have been run through the roof space of the kitchen extension and putting extra pipes in will probably mean pulling down some of the kitchen ceiling

cheers

bfob

 

[gavinda]

the cold feed and vent config is fine as long as they are the right way around. the bang should be investigated by a qualified individual. this is possibly explosive/poor ignition and needs sorting asap.