I would like to have an explanation of what a balancing valve does in a hot water heating system and when manual valves are used and when powered valves are used. Any and all information about these hot water heating system valves would be appreciated.

I hope the link below will help you, Thanks.

John

How to balance your central heating system. How to get your radiators all to the same temperature (http://www.diydoctor.org.uk/projects/balancingcentralheatingsystems.htm)

Manual valves are used for isolation and service so the entire system doesn't have to be drained to replace a pump.

Powered valves in a consumer system are generally used to turn on zones. In a commercial system they may be proportional. e.g. You want a particular loop temp.