User Guide

Technical Instructions 599 Zone Valve Series: Two-Way and Three-Way
Document No. 155-320P25
February 6, 2006
Page 4 Siemens Industry, Inc.
Operation
2-Way
Figure 3 shows the zone valve in the open or full flow
position. The valve spring provides the necessary force to
hold the stem in the raised or NO position.
In the event of power failure, the actuator returns to its
normal position; the actuator determines whether the
valve will fail open or closed. See the actuator Technical
Instructions for additional information.
Figure 3.
3-Way
Diverting
As the valve stem moves downward, the flow through the
NO port (AB-A) decreases and the flow through the NC
port (AB-B) increases. As the valve stem moves upward,
the flow through the NO port (AB-A) increases and the
flow through the NC (AB-B) port decreases.
In the event of power failure, the actuator returns the valve
to its normal position; the actuator determines whether the
valve fails with flow to port A or port B. See the actuator
Technical Instructions for additional information.
Figure 4.
Mixing
The 3-way zone valves are diverting valves. However, they may be used as mixing
valves under the conditions shown in Figures 5 and 6.
Figure 5. Mounting in the Return Flow.
Figure 6. Allowable Differential Pressure in Relation to the System Pressure.