Purging air from 3-zone closed loop system

TJack303

I am looking for some advice on how to purge air from my system, as I currently can't get any hot water to circulate in any of the zones. 2 zones are in-floor, one in the basement and one in the garage. The 3rd zone is for upstairs baseboard heaters.

Some background: I bought the place a little over a year ago and was told by the previous owners that the upstairs zone needed purged every year, for whatever reason it got air in the system and stopped circulating hot water. I did that last year and everything worked fine. 

With Temps getting cooler in northern Wisconsin I went to go test the system over the weekend. Originally only the upstairs zone wouldn't circulate water, so I attempted to purge it like I did last year. This time, however, it didn't seem to be as effective as last year. The system isn't connected to our domestic water and doesn't have a fill valve, so I hook a hose up from the nearby washing machine connection for the supply and run a second hose to the floor drain in the same room for the return, doing one zone at a time with all valves going back to the boiler closed. Last year it was easy to tell the air was getting out of the system, at first the flow on the return was really intermittent but in a short amount of time the flow became steady. This year however, I let it go for 20+ minutes and the flow on the return was still intermittent, constantly sputtering. 

We are on well water and we have issue with consistent water pressure, so I was thinking of buying a submersible pump to use to try and purge the zones. Is there any risk in doing this? What size pump should I go with? There's a 1/2 hp pump on Amazon that says it does 1900 gallons per hour with a 10' vertical rise. Should I go bigger? Smaller?

neilc

how do you set the system pressure? 12 #s?
and what type tank, bladder or air cushion?
any automatic vents ?
are you pumping away from the tank?
pictures of the boiler and circ(s), all in 1 shot, floor to ceiling

TJack303

neilc said:

how do you set the system pressure? 12 #s? and what type tank, bladder or air cushion? any automatic vents ? are you pumping away from the tank? pictures of the boiler and circ(s), all in 1 shot, floor to ceiling

It's at about 15#'s. There's an automatic damper for the boiler. Water heats up fine but doesn't circulate through the zones, even if I manually open each zone valve. I just turned it on to check again and right now I have hot water coming out the top of the boiler to the expansion tank then nothing past that. It's hard to get it all in one picture because it's a tight space and it's a pretty messy install, at least from my untrained eye.