HomeMy WebLinkAboutLetter; Auto fan Shut Down Requirements19
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St. Lucie County
Fire District
(561) 462-2300 FAX (561) 462-2325
P.O. Box 3030
2400 Rhode Island Ave.
Fort Pierce, FL 34948
AUTOMATIC FAN SHUT DOWN REQUIREMENTS
FOR AIR HANDLING SYSTEMS.
The requirements for automatic fan shut down in air handling systems are the
requirements of the Southern Standard Mechanical Code, 1994 edition, Chapter 406, .
and the National Fire Protection Association "Life Safety Code" N.F.P.A. 101.
In determining which code to comply with, the following information is necessary
1. A/C units make up a system and is referred to in the codes as an air
handling system.
2. The N.F.P.A. Life Safety Code, Occupancy Chapters 8 through 31
references Heating, Ventilation, and Air Conditioning and shall
comply with Section 101-7-2 of the Life Safety Code.
3. Section 101-7-2 requires air conditioning, heating, ventilating
ductwork, and related equipment to be installed in accordance with
• N.F.P.A. 90 A, Standard For The Installation of Air Conditioning and
Ventilation Systems, or N.F.P.A 90B, Standard for the Installation of
Warm Air Heating and Air Conditioning Systems.
4. N.F.P.A. 90A. Scope: This standard applies to all systems for the
movement of environmental air in structures that:
(a). Serve spaces over 25,000 cubic feet in total volume, or
(b). Serve buildings of Types III, IV, and V construction over
three stories in height, regardless of volume. The construction
types indicated are in accordance with N.F.P.A. 220.
5. N.F.P.A. 90A. For the purpose of this standard, a space is
considered as the entire building or a portion thereof separated
from other portions of the building by fire resistance rated
construction and whose environmental air does not mix with that of
any other space. For spaces not exceeding 25,000 cubic feet in
volume, reference the Standard Building Code, Chapter 406.
Page 1 of 4
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6. For spaces not exceeding 25,000 cubic feet in total volume, compliance
to The Standard Mechanical Code, 1994 Edition, shall be in
compliance.
7. Automatic fan shut down requirements, N.F.P.A. 90A.
a. Location: Smoke detectors listed for use in air distribution
systems shall be located: .
(1). Downstream of the air filters and ahead of any branch
connections in air supply systems of greater than 2,000
cfm capacity.
(2). At each story prior to the connection to a common return
and prior to any recirculation or fresh air inlet connection in air
return systems over 15,000 cfm capacity. and serving more than....
one s o .
Exception: No 1: Retum systems smoke detectors are
not required when the entire space served by the air
distribution system is protected by a system of area
smoke detectors.
Exception No. 2: Fan units whose sole function is to
remove air from inside the building to outside the building.
b. Function: Required smoke detectors shall automatically stop
their respective fan(s) upon detecting the presents of smoke.
Exception: Where the return air fan is functioning as part of an
engineered smoke control,system and a different mode is required.
C. Installation: Listed duct type smoke detectors shall be installed in
accordance with N.F.P.A. 72,, National Fire Alarm Code.
(1). When an approved protective signaling system, (fire alarm)
is installed in the building, the smoke detectors shall be connected
to the protective signaling system in accordance with N.F.P.A. 72
so that activation of any air distribution system smoke detector will
cause a supervisory signal to be indicated at a constantly
attended location, or will cause an alarm signal.
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wl (2). All detection devices used for the operation of
smoke dampers, fire dampers, fan control, smoke doors, and fire
doors shall be monitored for integrity in accordance with N.F.P.A.
72 -1 - 5.8 where connected to the fire alarm system serving the
protected premises.
(3). When smoke detectors are installed in a building not
equipped with an approved protective signaling system shall,
(a). cause a visual and audible signal in a normally
occupied area, and
(b). Smoke detector trouble conditions shall be indicated
visually, or audibly in a normally occupied area and shall be
identified as air detector trouble.
(c). The above signal requirements can be annunciated
with a simple Remote Test Station, with a Sounder.
8. Smoke detectors having power supplied separately from the signaling
system (fire alarm) for the sole function of stopping fans do not require
standby power.
9. Standard Mechanical Code, Automatic Fan Shut Down
requirements.
a. Systems serving buildings or spaces less than 25,000 cubic feet in
volume shall comply with the requirements of the Standard
Mechanical Code, Chapter 406, 1994 Edition.
b. Capacity from 2,000 - 15,000 cfm. Recirculating air systems shall
automatically shut down when heat within the system becomes
excessive, or exceeds 136 F. An automatic control (firestat) shall be in
the return air stream prior to any exhausting from the building or mixing
with fresh air makeup.
An approved smoke detector for duct installation may be used in
lieu of the firestat. The Fire Marshal recommends the use of a listed
duct type smoke detector be used in lieu of the firestat. A complete
building system of smoke detection that is connected to the fan system
for automatic fan shut down may be used.
C. Capacity less than 2,000 cfm.
Recirculating air systems with a fan capacity less than 2,000 cfm,
but serving an area used for egress, shall have automatic fan shut
down. This would be foyers, lobbies, stairways, corridors and
passageways. Page 3 of 4.
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10. Code Conflicts:
a. There is some confusion as to the installation of duct type
detectors in the supply air or return air systems. The important
advantages of detectors being in stalled in the supply air is the supply air
is filtered and will be free of dust that can collect on the detector(s).
Some manufactures specify the installation in supply air only.
b When duct type detectors are connected to a protective signaling
system (fire alarm), detectors shall be installed in the supply air in
accordance with NFPA 90-A. Fire alarm systems are Uniform Fire
Safety Standards and the requirements shall be in accordance with
NFPA 101 Life Safety Code and not the Standard Mechanical Code.
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