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AIR CURRENTS
Before a detector can sense a fire, the products of
combustion or smoke must travel from the fire to the
detector. This travel is especially influenced by air
currents; therefore, consider air movement when
designing the system. While combustion products tend
to rise, drafts from hallways, air diffusers, fans, etc., may
help or hinder the travel of combustion products to the
detector. When positioning a detector at a particular
location, give consideration to windows and doors, both
open and closed, to ventilating systems, both in and out
of operation, and to other factors influencing air
movement. Do not install a detector in the air stream of
a room air supply diffuser. It is better to position a
detector closer to an air return.
The distance that products of combustion or smoke
travel from a fire to the detector is not usually the shortest
linear route. Combustion products or smoke usually rise
to the ceiling, then spread out. Average ceiling heights of
8 to 10 feet do not abnormally affect detector response.
High ceilings, located in churches, warehouses,
auditoriums, etc., do affect detector response and should
be considered.
SPECIAL CEILING CONSTRUCTION FACTORS
Ceiling obstructions change the natural movement of air
and combustion products. Depending on the direction of
smoke travel, joists and beams can slow the movement
of heated air and smoke, while pockets between them
can contain a reduced level of smoke. Take obstructions
created by girders, joists, beams, air conditioning ducts,
or architectural design into consideration when
determining area protection. Refer to the Initiating
Devices chapter of NFPA 72 for Location and Spacing
requirements for specific types of construction; e.g.
beam, suspended, level, sloped and peaked ceilings.
TEMPERATURE – HUMIDITY – PRESSURE – AIR
VELOCITY
The temperature range for the OOH941 detector is 32 °F
(0 °C) to 120 °F (49 °C). Use the detector in
environments where the humidity is 15 % to 95 % RH
continuous non-condensing and 1 % to 99 % for short
duration (24 h to 48 h). Normal changes of atmospheric
pressure do not affect detector sensitivity. The air
velocity range is 0-4000 ft/min for open areas
applications. Follow detector spacing and location
requirements in NFPA 72 Chapter for High Air Movement
Areas and Control of Smoke Spread. The detectors can
also be installed in duct applications between 0 and
4000 ft/min. For duct installations follow detector
installation requirements in NFPA 90A, Chapter for
Special Ceiling Construction Factors. When the
detectors employ a fixed temperature rating of 165 °F
(74 °C) or less, they are intended for a maximum
installation temperature of 100 °F (38 °C).
LED INDICATOR OPERATION
The Model OOH941 contains an LED indicator capable
of flashing either one of three distinct colors: green,
yellow, or red. The microprocessor-based detector
monitors the following:
·
Smoke in its sensing chamber
·
Smoke sensitivity is within the range indicated on the
nameplate label
·
Internal sensors and electronics
Based on the results of the monitoring, the LED indicator
flashes the following:
Flash
Color
Condition
Flash Interval
(Seconds)
Green *
Normal supervisory operation.
Smoke sensitivity is within rated
limits.
10
Yellow
Detector is in trouble and needs
replacement.
4
Red
Alarm
1
No
Flashes *
Detector is not powered, or
replacement is needed.
–
* LED can be turned off. Please follow the corresponding
description of the Panel used.
DETECTOR PROGRAMMING
Each detector must be programmed to respond to an
address between 001 – 252.
·
To program the detector address, use the Model
DPU Device Programming Unit. Refer to the DPU
Manual, P/N 315-033260.
·
Record the loop and device number (loop address)
for the detector on the detector label and on the base
to prevent installing the detector in the wrong base.
The optional DPU label printer can be used for this
purpose.
Each detector provides pre-programmed parameter sets
which can be selected by the panel. The OOH941
provides two different alarm channels: the multi-criteria
(UL268) and direct in-duct (UL268A) channel with
supplementary heat detection, and the dedicated heat
(UL521) channel. They can be used simultaneously and
configured individually by the panel. Follow the
description and instructions provided in the operation
manual of specific control panel used. The OOH941 can
be set to the OOH941 Selectable Application Profiles,
OOH941 Selectable Fixed Temperature Threshold
Profiles and OOH941 Selectable Alarm Threshold
Setting Profiles shown in the tables below and to the
right.
Additionally, the detector can have another channel that
can be configured by the panel to have a low or high
temperature warning in the range from -4 to 120 °F
(-20 to 49 °C).
