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Chapter 3: Smoke control system programming
Smoke control
considerations and
sequencing
System response time
Smoke control activation is to be initiated immediately
after receipt of an appropriate automatic or manual
activation command. Smoke control systems activate
individual components such as fans and dampers in a
sequence necessary to prevent physical damage to
equipment. The total response time for individual
components to achieve operational mode should remain
within the limits set in NFPA 92A as a base requirement:
•
60 seconds for fan operation at smoke system
design rate
•
75 seconds for isolating damper travel
The Uniform Building Code (UBC), one of the three
model building codes in use in the US, establishes more
restrictive limits on smoke control system response
times. Section 905.14 of the UBC requires individual
components to achieve their desired operating mode
according to device:
Table 11: UBC response time requirements
Component
Control air isolation valves
Smoke damper closing
Smoke damper openings
Fan starting (energizing)
Fan stopping (de-energizing)
Fan volume modulation
Pressure control modulation
Temperature control safety
override
Positive indication of status
Note: Local codes may require different response times.
System event processing bandwidth
The demand placed on the system event processing
bandwidth cannot exceed 75% of the system response
time requirement. If any of the bandwidth demands
42
Response time
Immediately
15 seconds
15 seconds maximum
15 seconds maximum
Immediately
30 seconds maximum
15 seconds maximum
15 seconds maximum
15 seconds maximum
described below exceeds 75% of the system response
time limit requirement, call Application Engineering for
support.
Signature loop bandwidth demand
Each Signature loop can support a sustained rate of two
events per second. Estimate the Signature loop
bandwidth demand using the formula below.
Ln[x] / 2 < TL × 0.75
where:
•
Ln[x] is the number of events triggered by the
operation on each loop [x]
•
TL is the time limit
CPU board bandwidth demand
Each CPU board can support a sustained rate of
16 events per second. Estimate the CPU board
bandwidth demand using the formula below.
Cn[y] / 16 < TL × 0.75
where:
•
Cn[y] is the number of events triggered by the
operation on CPU board [y]
•
TL is the time limit
Network bandwidth demand
The VM life safety network can support a sustained rate
of 16 events per second at 38400 baud. Estimate the
network bandwidth demand using the formula below.
Nn / 16 < TL × 0.75
where:
•
Nn is the total number of events triggered by the
operation across the entire network
•
TL is the time limit
Activating the smoke control system
The fire detection system activates the smoke control
system automatically when smoke is detected in a
smoke control zone. A waterflow switch or heat detector
can also activate the smoke control system as long as
their piping and wiring are exclusive to the smoke control
zone.
VM-1 Smoke Management Application Guide
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