Operating Instructions

Chapter 2 – Applications
Basic Operation
11
Siemens Industry, Inc.
Owner's Manual, Apps 2920/2926
125-5109
2015-06-30
Chapter 2 – Applications
Basic Operation
The LCM-OAVS Room Pressurization with Two Fast-acting Venturi Air Valves (One
Suppy, One Exhaust) and Hot Water Reheat provides Direct Digital Control (DDC)
technology for pressure independent Variable Air Volume (VAV) and Constant Volume
(CV) laboratory room applications.
Application 2920 LCM-OAVS Venturi Fast Speed
The LCM is specifically designed to perform these functions in laboratories with VAV
fume hoods. This version of the LCM uses one supply duct with a reheat coil, one
exhaust duct and up to six fume hoods using an averaging and scaling module.
Pressurization is controlled by maintaining a selected difference between supply and
exhaust airflows and uses fast-acting electronic actuators (shipped separately) to
control the supply and exhaust Venturi air valves.
NOTE:
If desired, the LCM can be used without any fume hoods attached. In this case, MAX
HOOD VOL should be set to 0 cfm to disable the alarming that would occur if
MINHOODVOLTS is set to 1 Volt or more and the fume hood flow input drops below
.4 Vdc.
Pressurization is controlled by maintaining a selected difference between supply and
exhaust airflows.
Temperature control is determined by input from the Room Temperature Sensor
(RTS).
The LCM controls pressure, ventilation, and temperature. When these functions
conflict, the priorities are:
1. Pressurization
2. Ventilation (supply minimum may be overridden to maintain negative
pressurization)
3. Temperature