Hydrogen sensor location

Nexttimebud

Member
Location
Los Angeles
Occupation
Electrician
Good morning ,
We are installing a hydrogen detection system in a battery room of a data center , does anyone know if it falls under same codes as smoke detectors where the beam pocket is deeper than 12” a second detector needs to be added? Thanks
 
Is the hydrogen being used for something or is it discharged by the batteries?

There are mentions in NFPA 72 and NFPA 2.

Any method that can detect at a fraction of 4%. From NFPA 2, Annex L, "Alarm levels should be some set fraction of the hydrogen lower flammable limit, which in air is 4 vol%."

Most VRLA batteries have a sealed layer by either a mat or gel. I don't know if I have ever noticed a hydrogen detection system with VLRA batteries.

NFPA 2 has annex L which has a lengthy description on detection methods.
 
The system is being used to monitor levels of hydrogen in space, if to high Fire alarm system goes off and exhaust kicks on. The batteries are Lithium.
 
The system is being used to monitor levels of hydrogen in space, if to high Fire alarm system goes off and exhaust kicks on. The batteries are Lithium.

Are you sending the Data Center to the moon? lol What does in space mean?

You usually install detection because explosive quantities of a given compound are capable of being present. If nothing creates hydrogen then why monitor for it'? It could just be one of the many things Data Centers do to over engineer.

You most likely need to consult with the engineer of record on the sensor locations. Or whomever decided to put them on the plans and confirm the locations with them.
 
Back to the original question, does hydrogen sensors fall into same category as smoke detectors and if there is steel beams deeper than 12" do you add additional sensors between beams?
 
Back to the original question, does hydrogen sensors fall into same category as smoke detectors and if there is steel beams deeper than 12" do you add additional sensors between beams?

What code section are you using for the requirement of smoke detectors?
 
The 2002 edition of NFPA 72 requires that when beams project more than 12 inches below the ceiling and when ceiling heights exceed 12 feet, each bay (beam pocket) formed by the beams should/must be treated as a separate area
 
NFPA 72 17.10.2.4* -

"The selection and placement of the gas detectors shall be based on an engineering evaluation."

It depends on the type of sensor and other airflow conditions present. A gas sensor should be used to mitigate the condition prior to fire starting. A smoke detector is used to acknowledge the existence of a fire.

The rules are not the same. NFPA 72 acknowledges that. But you can not ignore the possibility of pockets being created. Someone familiar with the amount of possible hydrogen and the airflow of the room should be telling you where to mount the sensors.
 
Definitely not.
Well, not in normal operation, but hydrogen is one of many flammable as well as toxic gasses that are given off when the battery is in thermal runaway. However, at that point it is too late.

There are gas detectors used for li-ion battery installations that sense the off gassing that occurs when the batteries start to malfunction, but hydrogen is not one of the early warning gasses.

The types of gases released at this stage are predominantly battery electrolyte solvent vapors, such as diethyl carbonate, dimethyl carbonate
or other carbonate species used in electrolyte solvents. Detectors for these gasses can be used in conjunction with the battery management system to shut down the batteries in an attempt to prevent a complete thermal runaway.
 
VRLA or standard wet batteries do not usually off-gas hydrogen at a very high rate. You tend to get a gradual buildup of H2. As a result, the room will have a pretty flat concentration profile from floor to ceiling due to H2's very high diffusion rate. Locating the sensor at the ceiling should be sufficient. As always, follow the manufacturer's installation instructions.

That said, H2 sensing is not a good fit for monitoring LiON batteries. The major fire alarm manufacturers each have their own proprietary systems. Siemens has their Sinorix NXN N2 system which detects AND suppresses the fire. Xtralis has their Li-ion Tamer system.
 
VRLA or standard wet batteries do not usually off-gas hydrogen at a very high rate. You tend to get a gradual buildup of H2. As a result, the room will have a pretty flat concentration profile from floor to ceiling due to H2's very high diffusion rate. Locating the sensor at the ceiling should be sufficient. As always, follow the manufacturer's installation instructions.

That said, H2 sensing is not a good fit for monitoring LiON batteries. The major fire alarm manufacturers each have their own proprietary systems. Siemens has their Sinorix NXN N2 system which detects AND suppresses the fire. Xtralis has their Li-ion Tamer system.
How does that work since the Li-ion batteries can burn completely underwater?
 
Self-serving, but informative.

My understanding is that there is plenty of O2 in the battery chemistry and I don't see how N2 puts the fire out. From what I have read, the only way to put such a fire out is to provide enough cooling to prevent cells that are adjacent to the cells that are in thermal runaway from also entering into thermal runaway. Now if they were telling me that they were injecting liquid N2 into the cooling passages, I might believe that could prevent the expansion of the fire.
Note, I have a huge distrust of manufacturers information ever since the AFCI issue, when the manufacturers said, in order to get the AFCI into the code, they had a product that would do what they now tell us that the combination type AFCI will do...the only issue they made those statements some 13 years before the combination type AFCI even existed.
 
Top