Figure 5 shows a typical bypass control arrangement
on a cooling coil. The sketch shows that a balancing
valve is installed in addition to the bypass valve. The
balancing valve is adjusted to provide the same flow
resistance as the cooling coil. This arrangement provides
better control by the control valve, especially at low
loads. In many cases, a balancing valve is not used. As
an alternative to using a balancing valve, the bypass valve
is selected to provide the characteristics of the balancing
valve. (With this type of balancing valve, the bypass
path has a minimum flow resistance approximately equal
to the resistance of the controlled equipment.)