User Guide

Flowrite VF 599 Series Three-Way Valves Technical Instructions
Document Number 155-185P25
April 9, 2007
Siemens Building Technologies, Inc. Page 9
Operation,
continued
If this valve is used in diverting applications, the following conditions apply:
Diverting service with modulating control can use mechanical actuators such as the
SQX and SKB/D. The differential pressure must not exceed 90% of the maximum
differential pressure specified for the three-way valve in mixing service.
Diverting service with a pneumatic actuator can only be used with two-position control.
To change over from one port to another there must be no system pressure. The pump
is tuned off.
Sizing
The sizing of a valve is important for correct system operation. An undersized valve will
not have sufficient capacity at maximum load. An oversized valve can initiate cycling,
and the seat and throttling plug can be damaged because of the restricted opening.
Correct sizing of the control valve for actual expected conditions is considered essential
for good control.
Some variables that must be determined are:
• The medium to be controlled, such as water, etc.
• The maximum inlet temperature and pressure of the medium at the valve.
• The pressure differential that will exist across the valve under maximum load
demand.
• The maximum capacity the valve must deliver.
• The maximum line pressure differential the valve actuator must close against.
• See the Control Valve Selection and Sizing (AB-1) section of HVAC
Systems/Controls Reference Data (125-1853) for further recommendations.
See Tables 2 and 3 for valve capacities.
Mounting and
Installation
• Install the valve so that the flow follows the direction of the arrow indicated on the
valve body.
• For best performance, install the valve assembly with the actuator above the valve
body. The valve and actuator can be installed in any position between vertical and
horizontal. Siemens Building Technologies does not recommend installing the valve
assembly so that the actuator is below horizontal or upside down.
• Allow sufficient space for servicing the valve and actuator. See Table 9 for valve
body dimensions. See Figure 6 and Table 8 for dimensions of the service envelope
recommended around the actuator.
NOTE: Instructions for field mounting an actuator, wiring diagrams, and start-up are
covered in the Technical Instructions and Installation Instructions for each
actuator.