Zone valve question
I have a well mclain cgi gas fired hot water system boiler. We added a room on the second floor and want to make a seperate zone with a seperate thermostat. The boiler has one circulator pump which is on the return side of the system. Where should I install the two zone valves on the return or on the feed side of the boiler. Also I have been looking at the TACO zone valves. One last thing the original feed for the first floor was piped using 1 inch and the room on the secon floor was piped using 3/4.