NEC Hazardous Area Classification

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timm333

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Electrical Design Engineer
I have a question about hazardous area classification for battery room. NEC 500.6(A)(2) states that the areas which have hydrogen (batteries) shall be classified as Class I Group B. However hydrogen has a high flash point (1058 Deg F) and that much temperature is not possible in battery room. Because as per NEC Table 500.8(C), the maximum possible temperature of electrical equipment is for T1 type enclosure which is only 842 Deg F.

As 842 Deg F is less than 1058 Deg F, so I think hydrogen (battery room) should not be required to be classified. What do you guys think about it? Thanks
 
You may be a little confused on the Division VS Group of the gasses. Per 500.5 and 500.6 if hydrogen is present under normal operating conditions or under a fault condition then the area is A Class 1 Division 1 location, They hydrogen its self is a Class 1 Group B material. Your Battery room would be a Class 1 Division 1 area because of the unregulated presence of a Class 1 Group B material.

580.8(C) Is referring to the operating conditions under normal operation. This is more to protect users/servicers from injury due to this known surface temperature.

The concern is for that of arcing or other electronic ignition sources causing ignition of the Hydrogen. A contactor that is not rated for use in a Class 1 Division 1 location could have a small arc when making or breaking. This electrical arc can be up to 35,000 degrees. Plenty to ignite your hydrogen.

If you are looking to avoid hazardous classification. Then you will need to prove that the batteries cannot create an ignite able concentration of hydrogen.
 
See 480.10(A). The battery area probably does not need to be classified. The following is from the "enhanced content" that follows section 410.10(A) in LinK.
Ventilation is necessary to prevent classification of a battery location as a hazardous (classified) location, in accordance with Article 500.
Mechanical ventilation is not mandated. Hydrogen disperses rapidly and requires little air movement to prevent accumulation. Unrestricted natural air movement in the vicinity of the battery, together with normal air changes for occupied spaces or heat removal, normally is sufficient. If the space is confined, mechanical ventilation might be required in the vicinity of the battery. Hydrogen is lighter than air and tends to concentrate at ceiling level, so some form of ventilation should be provided at the upper portion of the structure. Ventilation can be a fan, a roof ridge vent, or a louvered area.
Although valve-regulated batteries often are referred to as “sealed,” they actually emit very small quantities of hydrogen gas under normal operation and are capable of liberating large quantities of explosive gases if overcharged. These batteries, therefore, require the same amount of ventilation as their vented counterparts. Of the primary types of battery chemistries used in storage battery systems and energy storage systems, only lithium-ion and sodium nickel chloride batteries do not require ventilation under normal or abnormal charging conditions.
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Yes that makes sense. Just in case we have to classify the battery room: then should we classify the whole battery room, or should the classified area end after 3 feet from the edge of the battery?

If the classified area ends after 3 feet from battery, then the breaker of the battery does not have to be hazardous-rated. Because in this case a non-hazardous (unclassified) breaker is allowed by NEC 240.21(H).
 
timm333 said:
Yes that makes sense. Just in case we have to classify the battery room: then should we classify the whole battery room, or should the classified area end after 3 feet from the edge of the battery?

If the classified area ends after 3 feet from battery, then the breaker of the battery does not have to be hazardous-rated. Because in this case a non-hazardous (unclassified) breaker is allowed by NEC 240.21(H).
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If the room is classified it would likely only be near the ceiling. Maybe 18" down like is required for major repair garages where lighter than air fuels such as hydrogen or natural gas are used. See Table 511.3(D).

You really need someone with experience in this to provide the area classification drawings that are required by 500.4.

The rule in 480.10(A) requires ventilation to prevent an accumulation of hydrogen with in the flammable range. However it does have very wide flammable range with LEL being 4% and UEL being 75%.
 
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