Zone valve question

[eagleslawyer]

My friend's home has three zone two pipe radiator setup. Somehow system gets full of air. Handyman told her the zone valves are on wrong side of boiler (they are on feed to the rads) and should be on the returns.


Any ideas, suggestions?

thanks

 

[NHmaster3015]

should make no difference. Usually they are on the feeds though. The air is some other issue.