Operating Instructions

Laboratory Room Controller Owner's Manual
3-16 Siemens Building Technologies, Inc.
For laboratories that employ an unoccupied mode, the alarm limit can be set separately for
occupied and unoccupied periods. Enter the selected alarm levels into the points OC V ALM
LVL and UC V ALM LVL. If there is no difference between occupied and unoccupied periods,
set the two points to the same value.
Troubleshooting Laboratory Air Flow
When problems arise with the laboratory ventilation and pressurization system, you can take
a systematic approach to identify and correct the problem. This section outlines the
recommended processes. Symptoms are listed; each followed by a series of questions
designed to identify the problem.
Problem 1: Observed Positive Pressurization
If positive pressurization is observed physically, complete the following steps:
1. Is it a steady or dynamic condition? If it is dynamic, go to question two. If it is steady, go
to question three.
2. Is it related to moving fume hood sashes, or does it continue when the sashes are still?
If it is related to sash motion, the room pressurization system should be adjusted. This
may involve tuning loops and adjusting the flow difference (VOL DIF STPT) for the room.
Contact your Siemens Building Technologies, Inc. branch for assistance.
If positive pressurization continues when the fume hood sashes are stationary, use the
process described in
Problem 4: Unstable Airflow
.
3. Does the controller show the problem? Read the VOL DIFFRNC point. If it shows a
negative value, or a value that is much less than the set point, then the measured supply
flow is too high for the exhaust and the controller has recognized this situation. Look for
overrides such as dampers (SUP DMPR CMD, etc.) and set points (SUP VOL STPT).
Also, look for flow controls that cannot meet the set point (SUP AIR VOL, etc.).
If the controller shows a positive value that is reasonably close to the set point (VOL DIF
STPT), then there is a flow sensing problem. Look for failed or overridden flow readings
(SUP VOL, HOOD VOL, etc.) and for readings that are obviously incorrect (OTHER SUP,
OTHER EXH, etc.). Also, check HOOD VOL against the reading from the fume hoods
controllers. Use the Pressure Report in CIS, the field panel, or Insight to investigate.
If the procedures listed above do not fix the problem, the flow sensors may need to be
recalibrated. Contact your Siemens Building Technologies, Inc. branch for assistance.