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The photos attached is of a
system is a seven zone basboard heat system with three boilers. There is a total of 11 circulators. One for each boiler, one for each zone, and one main system circulator. There are no zone valves. Over the last year three circulators have been replaced. When the system was purged of air, the building heated fine. About three weeks after that, the building was not heating, and it appeared air was the issue. The air was purged again, and the building heated fine again. That was the end of last winter, and so far this winter, it has happed once where the system needed to be purged. We are using the same procedure to purge the air that is shown in the the instructions that are shipped with Taco circulators where the water is sent through a zone at near city water pressure, the isolation valve on the return side of that zone is closed, and the boiler drain located in front
of it is opened, and the air is purged from the zone. This seems to keep the system going for a few weeks, and then it needs to be done again. Any suggestions would be much appreciated. Thanks to all.