How I removed and purged air from my hydronic radiant heat boiler Pex tubing closed loop system when filling by adding water and anti freeze for the first time setup. It was a little difficult for me to figure out to to fill the Pex lines and purge all the air out of the lines. I had a hard time finding videos that explained the process very well. Your system may be different but hopefully this will help to give you an idea of what I went through.

http://bit.ly/WaterTransferPump here you can find water transfer pumps to purge the system.
http://bit.ly/TempraBoiler here is the Tempra Boiler water heater that I have. I use the 12, You may need a bigger one based on your sq footage.
Let me know how it goes for you. Thanks for watching!