I was called out today on a boiler in a hydronic heating system that was limiting out.
The house was being remodeled, and a plumber had emptied the water out of the system while doing some work on the baseboard heaters. He didn't bother filling the system.
This system had probably never been opened since it was built 17 years ago. I couldn't get the water to circulate in either of the two upstairs zones (bad zone valve wouldn't open for the basement).
I purged all the air that would come out of the purge points until I got all water. The B&G 1/12 HP pump was cranking away fine. The isolation valves are all open, as far as I can find them anyway.
I'm wondering if it needs more places to bleed out air? There were a couple of purge points on each pipe run.
This has stumped me so far. I invite comments on what I may be missing.