Is there a method to find where system is taking on air?

Joseph_4

I have a customer. monoflo system where he called me a few months ago, lots of noise in pipes and different rooms not heating. bled system by building pressure and eventually got all rooms hot and no more noise from pipes- air out of system.

He says the problem is back. He does have a #67 auto air vent on top of boiler. system is obviously still taking on air slowly. Any suggestions what to do or how to locate where air is coming in from?

Thanks

Joe 

Gordan

What kind of boiler? What kind of expansion tank, piped where?

What's the system static pressure? What does it read when fully up to temp? Is there any evidence of pressure relief valve popping? Is the system connected to a makeup line and is that line open?



I've found that it's not unusual to have to bleed the system more than once - it's not just air pockets but also dissolved air. By bleeding I mean actually letting air out of emitters by opening an air vent. I'm not sure what you mean by "bled system by building pressure."

Brad White

Where is

the expansion tank connected? That is the #1 factor to inducing air into the system, especially if the circulator is a high-head type and the system pressure at that point is low.



If the expansion tank connection point is on the discharge of the circulator, you may actually draw a slight vacuum on the suction side. Air can be drawn in via automatic air vents and valve stem packings.



If the expansion tank is properly connected as close to the circulator suction side as possible, the pressure at that point will not change appreciably whether the circulator is running or not.



If you have a diaphragm tank (vs. a standard captive air tank where air and water actually meet), that also eliminates a source of air to be dissolved into the system over time.



Take care of those but especially the circulator vs. expansion tank connection location and I bet you solve the problem.



Think about it this way: Absent the situations described above, how else would air get into a system pressurized to at least 12 psig?