Balancing Valves. Balancing valves (Circuit Setters) are used to impose artiﬁcial head in all pipe routes besides the critical one to prevent short circuiting (excessive ﬂow through lower pressure drop paths that results in insufﬁcient ﬂow through the highest pressure drop path). These valves are usually located on the return side (outlet) of the device as because this subjects their elastomers to lesser extremes of temperature and pressure, extending their lives. The most common type of balancing valve consists of a variable oriﬁce and two pressure taps to measure the pressure differential across the valve. The ﬂow rate is determined by measuring the pressure drop and noting the opening position of the variable oriﬁce. Then a chart is used to ﬁnd the ﬂow rate.
Another type of balancing valve uses a ﬂow sensor to measure the ﬂow rate, plus some type of throttling valve, impeller trimming, or a variable speed drive to limit the maximum ﬂow rate. This approach is generally more expensive, but has lower pressure drop and reduces pumping energy.
Automatic ﬂow-limiting valves are preferred by some designers. They consist of a spring and variable oriﬁce to limit the ﬂow rate to the maximum intended for that ﬂow path. They are commonly applied on heat pumps.
One apprehension with this type of control device is that there is often no way to measure ﬂow other than to assume that the automatic ﬂow limiting valve is operating properly. There is also no way to adjust the maximum ﬂow rate without replacing the automatic balancing valve. The advantage is that no manual balancing is required if they operate properly and are not fouled by debris in the piping.
There is also a combined balancing valve which includes a shutoff valve.
There are 2 ports which are located on each side of the balancing valve for measuring the input and output flow rate for balancing.