No flow in one loop

Steven Wolhandler

1970's vintage system. three loops that leave boiler from common manifold and return to a common manifold which has one circulation pump. There's a valve on each return pipe just before it goes into the common manifold, and a valve on the bottom of the common cast pipe between the circulation pump and the boiler. There's a pressure overflow valve and a regulator on the water in pipe, with a manual override to force water into the system.

One loop was noisy with gurgling - that i assumed was stuck air. I opened put a hose onto the valve on that loop's return, ran it into a large bucket and opened it. Air came out. I shut it and opened it a bunch and air came out each time. Then I manually opened the water input valve and water pushed out of it with more force and air came out. Now that loop is stone cold.

Opps!! what am I doing wrong? What pressure should the boilder gauge read? What temperature?

Richard

Purging loop

Have fould when purging system, to get the water pressure around 25psi and hold at that pressure. with a hose on the return line purge valve and close the return line valve on that loop. turn off the power to the system, do not want the pump to run. Open the purge valve 1/2 way and purge the loop. Need to keep the pressure up. After the loop is purged, open all the return valves and turn on system, if there is still a air noise, crack open the purge valve with the system running and let the pump move the air. Try these and let me know