Application

Overview
Hardware Inputs
5
Siemens Industry, Inc.
Application Note, App 2923
140-1347
2015-07-07
Overview
Application 2923 controls pressurization, ventilation, and room temperature in a
laboratory room served by one single-duct supply terminal with a reheat coil, one
general exhaust terminal, and up to six fume hoods (multiple fume hood flow signals
must be averaged using an averaging and scaling module. Pressurization is controlled
by maintaining a selected difference between supply and exhaust airflows.
This version of the LCM uses conventional supply and exhaust actuation (rather than
high speed actuation). Therefore, it should be used only where rapid room response to
fume hood volume changes is not required. Fume hoods used in conjunction with
these applications should be constant volume or slow actuation.
NOTE:
Application 2923 can be set up to operate without a supply box, or without a general
exhaust box. See the
Application Notes section for more information.
Application 2923 uses floating control electronic actuators for both supply and exhaust
damper control. A standard 0 to 10 Vdc actuator is used for the hot water valve.
NOTE:
The LCM controls pressure, ventilation, and temperature. When these functions
conflict, the priorities are:
• Pressurization
• Ventilation (supply minimum may be overridden to maintain negative pressurization)
• Temperature
Temperature control is determined by input from the room temperature sensor.