Application

Sequence of Operation
BACnet
5
Siemens Industry, Inc.
Application Note, App 6752
140-1322
2015-07-07
Overview
Application 6752 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 6752 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 6752 uses slow Venturi Air Valves for both supply and exhaust control. The
Venturi valves are each driven by a 0-10V analog signal. 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 overridden by specified flow limits for the air
terminals)
Temperature control is determined by input from the room temperature sensor.