4.3.3 Airbound Loops. If enough air bubbles gather at the high point of a piping
loop, a gap in the fluid may form.
Now that the piping loop is no longer completely filled, the circulating pump must
work against the effects of gravity. This usually means no flow occurs, since the
pump was not designed for this condition. (Figure 4-5)
An Airbound Collector
Piping with air in it is called "airbound." Flow will be obstructed or stopped. This
occurs most often in collector loops, but is also possible in storage piping. Some
common causes are:
incomplete filling of the solar loop in closed loop systems
leaks admitting air into solar loops
ruptured expansion tank diaphragms.
o dissolved air in potable water forming bubbles which are not vented
out of piping and tanks (usually aggravated by bad or missing air
4.3 TROUBLESHOOTING OPERATIONS