Fire Alarm - Unit Shutdown upon detection

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cwlodyka

Member
This may be a rather general and intepretive question, so I would appreciate any thoughts others may have...

I am not a Fire Alarm expert, I know it is typical to shut down a local AHU or AC unit when smoke is detected through the local return air detector. However, I am working in a data center where cooling is 100% critical to the space. Essentially we have four AC units dedicated to a single room for a data center (so this room is isloated from any other part of the buildings HVAC system.)

In this situation is there a severe disadvantage to keeping the unit running if smoke is detected? Say, if there was a fire would we essentially be feeding the fire, spreading the smoke, etc? This would be preferred to avoid any 'nuisance' or 'false' detection and subsequent shutdown of the units.
 

iwire

Moderator
Staff member
Location
Massachusetts
If the unit is over 2000 CFM which it surly is, you are required to shut it down if smoke is detected in it's return.

I don't believe you must shut the unit down if another unit in another area has sensed smoke in its return.
 

RICK NAPIER

Senior Member
Location
New Jersey
This requirement is usually found in the IMC article 606. Listed below is an exception that sounds as if it applies to this instilation.

606.2 Where required. Smoke detectors shall be installed where indicated in Sections 606.2.1 through 606.2.3.

Exception:
Smoke detectors shall not be required where air distribution systems are incapable of spreading smoke beyond the enclosing walls, floors and ceilings of the room or space in which the smoke is generated.

This is important in locations such as you have and clean rooms use in the pharmaceutical industry that when they loose positive pressure it can take months to have the rooms recertified by the FDA.
 

cwlodyka

Member
If the unit is over 2000 CFM which it surly is, you are required to shut it down if smoke is detected in it's return.

I don't believe you must shut the unit down if another unit in another area has sensed smoke in its return.

Per the 2009 IFC I see the requirement for the smoke detectors in units over 2000 cfm but I do not see the requirment where the unit needs to be shut down upon detection. Is this a standard requirement for any return air sensing?
 

cwlodyka

Member
Thank you guys for the responses, however I realized the exception and our client does not practice the exception in the desire of the earliest possible protection to detect their equipment.

I guess upon my review and these responses my single question is that is it required to shut-down the units when in alarm???
 

steve66

Senior Member
Location
Illinois
Occupation
Engineer
Thank you guys for the responses, however I realized the exception and our client does not practice the exception in the desire of the earliest possible protection to detect their equipment.

I guess upon my review and these responses my single question is that is it required to shut-down the units when in alarm???

Yes, I don't know the code reference offhand, but if a duct detector is required, I'm sure it is required to shut down the HVAC air supply.

But as Ron and Rick have mentioned, you application meets the exception. Since you meet the exception, if you install a duct detector, it would be optional. Since it is optional, I don't think it needs to shut down the HVAC.
 

skeshesh

Senior Member
Location
Los Angeles, Ca
Yes, I believe its under IMC 609. I don't have the reference at hand but I took a look at the California Mechanical Code which is based on the international code and its under 609:

Code:
609.0 Automatic Shutoffs.
Air-moving systems supplying air in excess of 2000 cubic
feet per minute (944 Lis) to enclosed spaces within buildings
shall be equipped with an automatic shutoff. Automatic
shutoff shall be accomplished by interrupting the power
source of the air-moving equipment upon detection of smoke
in the main supply-air duct served by such equipment. Smoke
detectors shall be labeled by an approved agency, approved
and listed by California State Fire Marshal for air duct installation
and shall be installed in accordance with the manufacturer's
approved installation instructions. Such devices shall
be compatible, with the operating velocities, pressures,
temperatures, and humidities of the system. Where fire detection
or alarm systems are provided for the building, the smoke
detectors required by this section shall be supervised by such
systems, and installed in accordance with NFPA 72 and the
California Building and Fire Codes.
Exceptions:
(1) When the space supplied by the air-moving equipment
is served by a total coverage smoke-detection system
complying with the California Fire Code, interconnection
to such system may be used to accomplish the
required shutoff.
(2) Automatic shutoff is not required when all occupied
rooms served by the air-handling equipment have direct
exit to the exterior and the travel distance does not
exceed 100 feet (30,480 mm).
(3) Automatic shutoff is not required for Group R, Division
3 and Group U Occupancies.
(4) Automatic shutoff is not required for approved smokecontrol
systems or where analysis demonstrates shutoff
would create a greater hazard such as may be encountered
in air-moving equipment supplying specialized
portions of Group H Occupancies. Such equipment shall
be required to have smoke detection with remote indication
and manual shutoff capability at an approved location.
(5) Smoke detectors that are factory installed in listed airmoving
equipment may be used in lieu of smoke detectors
installed in the main supply-air duct served by such
equipment.

For what it's worth I've provided automatic shut-down very recently in data rooms for a major university out here. I'm pretty sure that the research data they collect is pretty valuable although they may have remote back-up or other measures that I'm not aware of. I used exception 1 to avoid providing a duct detector and use the area coverage in the room for shut-down but the shut-down was required. I have used exception 2 in the past, but it was a sort of community center building in a public park where it was possible to do this and I highly doubt your project would fit that.
 

gadfly56

Senior Member
Location
New Jersey
Occupation
Professional Engineer, Fire & Life Safety
The first thing to consider is what regulations are in place by consulting your location's adopted building codes and/or consulting with the AHJ. In general, for the situation you describe, there is no point to shutting down the AHU's. Consider the purpose of shutting down the AHU; to prevent the spread of smoke to other areas served by the HVAC system. Here, there are no other areas. Also condsider that the signal from the duct detectors is frequently reported as a supervisory condition, not an alarm condition. Your data center should be protected by a clean agent system. In the event of a fire condition, the clean agent system should activate. Do you not have this?
 

ron

Senior Member
The first thing to consider is what regulations are in place by consulting your location's adopted building codes and/or consulting with the AHJ. In general, for the situation you describe, there is no point to shutting down the AHU's. Consider the purpose of shutting down the AHU; to prevent the spread of smoke to other areas served by the HVAC system. Here, there are no other areas. Also condsider that the signal from the duct detectors is frequently reported as a supervisory condition, not an alarm condition. Your data center should be protected by a clean agent system. In the event of a fire condition, the clean agent system should activate. Do you not have this?

Why have the hassle of a clean agent system? Most DC's that I'm in have a pre-action sprinkler, no clean agent.
 

jeremysterling

Senior Member
Location
Austin, TX
vesda

vesda

Very Early Smoke Detection or ASD (Aspirating Smoke Detection) can provide you with earlier alarm that provides you time to investigate before securing your air movement.
 
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