We have an ASD and point detection system for the cabinet. Are you suggesting to utilize the ASD only as a primary detection and the point detection to trigger the fire suppression?
As a safeguard when releasing Clean Agent suppression, we recommend two devices in alarm for initiating a release. As an example, the sequence could include a spot-type smoke detector plus Fire 2 (4th alarm level) of an ASD detector for release initiation.
Since ASD has around 4 stages of alarms – what if we integrate the fire suppression with the ASD – 4th stage alarm?
Correct, and couple Fire 2 of the ASD detector with alarm from a spot-type smoke detector. To ensure release initiation doesn’t occur too early, we recommend Fire 2 being set at a threshold equivalent to achieve Standard Fire Detection (Class C for EN-54) sensitivity at each sample hole, which is about 8% obs/m (2.5%obs/ft). To achieve this, simply take the target hole sensitivity and divide by total number of holes on the ASD detector. The resulting number is the alarm threshold to be programmed for Fire 2.
The OneU in-rack fire detection and suppression system takes care of the fire within the specific server rack. However, how does the rack integration of spot and ASD detection vary from the OneU in-rack protection method?
The spot and ASD detection are appropriate for in an open rack fire protection where area detection and suppression serving the space would be applicable. The OneU in-rack system is appropriate for protection of fully enclosed cabinets, where the OneU would be applicable in serving the enclosure, since a fully enclosed cabinet would be isolated from fire protection elements serving the room.
There is a requirement for fire detection and protection of a metal container / compartment – which is used to store Lithium – Ion batteries. Which detection and suppression system do you recommend?
A Li-Ion battery installation is a Class C hazard according NFPA 2001 with live electrical equipment. We recommend ASD and point detection for early warning and to trigger a VSH1230 suppression system. However, Li-Ion batteries could also go into thermal runaway. It has been found in various tests, that an CO off gas detection is an early indicator for most Li-Ion cells going into thermal runaway. Based on a risk evaluation adding a gas detector into the ASD suction pipe allows to power down and isolate the Li-Ion batteries. Once the batteries are in thermal runaway cooling stops the process and water is a good option.
What are the appropriate standards, codes, and recommended practices in regard to keeping cooling systems (CRAC/CRAH/AHU) operational during gas suppression?
There isn’t a definite answer whether to shut down the HVAC/CRAC units before suppression agent discharge to maintain the concentration and to avoid circulating of smoke and aggressive gases or to damper off air intakes and the keep HVAC/CRAC unit recirculating cool air and suppression agent to prevent overheating of equipment.
The NFPA research foundation started to evaluate the impact of high air flow on the effectiveness of a clean agent system.
Another source is FM Global Data Sheet 5-32, section 22.214.171.124.13
126.96.36.199.13 For HVAC systems that do not introduce makeup (outside) air, the forced air distribution system does not need to be shut down when both of the following are provided:
A. A cooling air system that only recirculates air within the data processing equipment space (e.g., CRAH and CRAC) unless the data processing equipment is interlocked to shut down on agent discharge.
B. Sufficient clean agent is provided for the volume of HVAC system ducts and components open to the protected space as part of the total hazard volume
Another source is NFPA 2001
5.3.6* Other than the ventilation systems identified in 188.8.131.52, 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.
A.5.3.6 …………. Where recirculating ventilation is not shut off, additional agent could be needed to compensate for room leakage during the hold time.
184.108.40.206 If not shut down or closed automatically, the volume of the self-contained recirculating undampered ventilation system ducts and components mounted below the ceiling height of the protected space shall be considered as part of the total hazard volume when determining the quantity of agent.
Another source is NFPA 75:
9.4.5 Where operation of the air-handling system would exhaust the agent supply, it shall be interlocked to shut down when the extinguishing system is actuated.
A.9.4.5 This provision requires that all environmental design criteria – for example, damper closure, fan shutdown, and sealed openings – be carefully maintained to ensure that needed concentration for extinguishing will be achieved. It is preferable, but not essential, to de-energize ITE prior to discharge if ITE shutdown does not cause major service interruptions.
Bottom line is that it is essential to maintain the required clean agent concentration inside the enclosure during the hold time. It’s obvious that a cooling system could have an adverse effect and the provisions outlined above need to be observed if a cooling system shut down is not an option.