Shutdown CRAC Units with FM200 Activation?

7/8/2025

I have an IT room with FM-200 under the raised floor and a pre-action sprinkler system at the ceiling. Contractors are replacing CRAC units.

Should the CRAC units be connected to the suppression system to shutdown upon activation of the FM200 system?

I have done 2 days of research with no answer. Thanks in advance.

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5 Comments

Pete H

7/8/2025 06:36:05 am

https://www.meyerfire.com/daily/shutdown-crac-unit-for-clean-agent-discharge

This was previously discussed on the forum here.

The useful part of NFPA 2001 (2018) that I see in this discussion was:

5.3 Enclosure
5.3.6 Other than the ventilation systems identified in 5.3.6.2, forced-air ventilating systems, including self-contained air recirculation systems, shall be shut down or closed automatically where their continued operation would adversely affect the performance of the fire extinguishing system or result in propagation of the fire.
5.3.6.1 If not shut down or closed automatically, the volume of the self-contained recirculating undampered ventilation system ducts and all components mounted below the the ceiling height of the protected space shall be considered as part of the total hazard volume when determining the quantity of agent.
5.3.6.2 Ventilation systems necessary to ensure safety shall not be required to be shut down upon activation of the fire suppression system. An extended agent discharge shall be provided to maintain the design concentration for the required duration of protection.

----

Short answer: yes, unless you want to consider their volume as part of the total hazard when determining the quantity of agent.

Mark Harris

7/8/2025 08:25:12 am

Halocarbon clean agents are heavier than air so if unit is shut down the agent will leak and cause a descending interface (minimum design concentration level height will drop). This is considered as part of the door fan test and ceiling height verses top of protected equipment.

As Pete notes if you do not shut down you will need to consider any additional volume. If the CRAC unit is in room and return is on unit (verses a plenum above ceiling) this may not be an impact. If unit stays on over time leakage will result in depleted concentration but the air movement keeps the concentration similar in entire room (verses the descending interface).

The Fire Suppression Systems Association (FSSA) just put out a white paper about this that suggests 15% more agent. Here is the link: https://www.fssa.net/fssa-white-papers. IT Managers fear their equipment overheating as much as fire so hence the interest from FSSA.

Glenn Berger

7/8/2025 08:31:47 am

The comment does not mention if power to the Data Equipment will be terminated upon fire suppression system activation. The comment also does not mention if the CRAC Unit only serves that one room. I have come across some clients who will require a "centralized" room for CRAC Units to serve multiple ITE spaces.

If power is terminated then shutting down the CRACs may be appropriate.

If the power is maintained, then shutting the CRACs will cause additional heat to build up in the space and not be the best solution.

Anthony

7/8/2025 08:59:40 am

The are should be air seals at the time of clean agent discharge for the appreciate amount of time per NFPA 2001.

However additional engineering controls need to be in place to lower the power on any computing in the area. With the cooling shut down the commuters WILL overheat and create an additional hazard.

The point of the FM-200 system is to reduce the failure of the whole system it would be pointless to have the physical computers(severs/racks ect) melt when a single unit fails.

Franck

7/8/2025 09:53:29 am

That’s a complex question as the FM200 is apparently only under the raised floor (preaction sprinkler for the room itself) and the concentration has been calculated on this quite limited volume only.

If your CRAC system is not impacting the volume under the raised floor, no need to stop it to maintain a correct concentration of gas. If the ventilation system is impacting the volume under the raised floor, the airflow needs to be stopped prior to the activation of the gas protection system, otherwise the gas will be diluted in the entire room and the minimum required concentration will never be maintained for 10 minutes.

This being said, from a fire prevention standpoint it would be good to stop it anyway, as it is sometimes a quite high ventilation system that may also have an impact on the efficiency of the sprinklers (activation at the ceiling may be impacted by high airflow velocities and sprinklers away from the fire area may activate, creating more water damages on equipment not involved by the fire).
But then, we are in the battle between sprinkler efficiency and technical requirements from IT people who want to keep the cooling for the equipment.

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Shutdown CRAC Units with FM200 Activation?

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