Hello, I am going to be connecting a wood furnace to my Crown Boiler with a plate heat exchanger and would like some info on draining and filling back the system and then bleeding the air out. My system uses three zone valves on the return line, sends hot water to water to air exchangers in the attic via pex tubing and then heats the house with forced air (hydronic heating), the circulating pump is on the return line after the zone valves, there is an expansion tank on the hot supply line, an automatic low water cut off switch on the supply as well .
I first need to drain my boiler, to do this I believe that I just close the supply line and open the drain at the bottom of the return line. After connecting the plumbing I believe I just open the cold supply line and the automatic low water cut off should fill the system. I do not think there are any bleeder valves on the pex tubing or in the air handlers in the attic. There is a gateway valve on the return line before the three zone valves and on the bottom of the return line after the zone valves before the pipe enters the boiler. I think the only way to bleed the air out of the system is with the gate valves. There is also something ontop of the expantion tank that has a valve like what you see on a tire that I think is for bleeding, but I am not sure.
Any advice on how to do this would be greatly appriciated.

I cannot possibly help much but to tell you.

You need auto bleeder valves at the highest point in your system. That means in the attic. It is a good possibility that the system will never bleed correctly without them. There are auto bleeders available that use adapters and 1/4 inch copper tube so they can be plumbed to the outside near the air vents under the overhang to prevent water damage from a stuck bleeder float.


See below

Automatic Air Valves For All Hot Water and Solar Heating Systems - Maid-O'-Mist® - Illinois (http://www.maid-o-mist.com/autoair.html)


I suggest you read all documents about the parts on your system so you know what is expected of each one. If you do not have the documents I suggest you find them by using Google as a search engine. Good luck on your project.