Richard Cummins
Member
- Location
- Chattanooga TN
My question is on the interpetation the work space about a battery system. The passage below is out of the 2011 NEC. My question is the requirment for work space. We normally bolt the battery rack to the wall for stability. I have an inspector that wants the battery rack with 3' of clearance all the way around the battery rack. The batteries are an ungrounded system. What is your interpetation of work space about the battery system?
480.9 Battery Locations.
Battery locations shall conform to 480.9(A), (B), and (C).
(A) Ventilation. Provisions shall be made for sufficient diffusion and ventilation of the gases from the battery to prevent the accumulation of an explosive mixture.
Compliance with 480.9(A) is necessary to prevent classification of a battery location as a hazardous (classified) location, in accordance with Article 500.
The intent of 480.9(A) is not to mandate mechanical ventilation. 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 may 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, roof ridge vent, or louvered area.
Although valve-regulated batteries are often 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.
(B) Live Parts. Guarding of live parts shall comply with 110.27.
Batteries should be located in clean, dry rooms and be arranged to provide sufficient work space for inspection and maintenance. Provisions must also be made for adequate ventilation, to prevent an accumulation of an explosive mixture of the gases from the batteries.
The fumes given off by some storage batteries are very corrosive; therefore, wiring and its insulation must be of a type that withstands corrosive action [see 310.10(G)]. Special precautions are necessary to ensure that all metalwork (metal raceways, metal racks, etc.) is designed or treated to be corrosion resistant. The battery racks shown in Exhibit 480.1 are coated with a nonmetallic outer covering as required by 480.8(A) that insulates and provides protection against the corrosive action of fumes from charging batteries and any electrolyte that may escape from the cells. Manufacturers sometimes suggest that aluminum or plastic conduit be used to withstand the corrosive battery fumes, or, if steel conduit is used, that it be zinc coated and corrosion protected with a coating of an asphaltum-type paint (see 300.6).
Overcharging heats a battery and causes gassing and loss of water. A battery should not be allowed to reach temperatures over 110?F, because heat causes a shedding of active materials from the plates, which will eventually form a sediment buildup in the bottom of the case and short-circuit the plates and the cell. Because mixtures of oxygen and hydrogen are highly explosive, flame or sparks should never be allowed near a cell, especially if the filler cap is removed.
Exhibit 480.1 A well-arranged battery room with batteries installed on corrosion-resistant racks. (Courtesy of the International Association of Electrical Inspectors)
(C) Working Space. Working space about the battery systems shall comply with 110.26. Working clearance shall be measured from the edge of the battery rack.
480.9 Battery Locations.
Battery locations shall conform to 480.9(A), (B), and (C).
(A) Ventilation. Provisions shall be made for sufficient diffusion and ventilation of the gases from the battery to prevent the accumulation of an explosive mixture.
Compliance with 480.9(A) is necessary to prevent classification of a battery location as a hazardous (classified) location, in accordance with Article 500.
The intent of 480.9(A) is not to mandate mechanical ventilation. 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 may 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, roof ridge vent, or louvered area.
Although valve-regulated batteries are often 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.
(B) Live Parts. Guarding of live parts shall comply with 110.27.
Batteries should be located in clean, dry rooms and be arranged to provide sufficient work space for inspection and maintenance. Provisions must also be made for adequate ventilation, to prevent an accumulation of an explosive mixture of the gases from the batteries.
The fumes given off by some storage batteries are very corrosive; therefore, wiring and its insulation must be of a type that withstands corrosive action [see 310.10(G)]. Special precautions are necessary to ensure that all metalwork (metal raceways, metal racks, etc.) is designed or treated to be corrosion resistant. The battery racks shown in Exhibit 480.1 are coated with a nonmetallic outer covering as required by 480.8(A) that insulates and provides protection against the corrosive action of fumes from charging batteries and any electrolyte that may escape from the cells. Manufacturers sometimes suggest that aluminum or plastic conduit be used to withstand the corrosive battery fumes, or, if steel conduit is used, that it be zinc coated and corrosion protected with a coating of an asphaltum-type paint (see 300.6).
Overcharging heats a battery and causes gassing and loss of water. A battery should not be allowed to reach temperatures over 110?F, because heat causes a shedding of active materials from the plates, which will eventually form a sediment buildup in the bottom of the case and short-circuit the plates and the cell. Because mixtures of oxygen and hydrogen are highly explosive, flame or sparks should never be allowed near a cell, especially if the filler cap is removed.
Exhibit 480.1 A well-arranged battery room with batteries installed on corrosion-resistant racks. (Courtesy of the International Association of Electrical Inspectors)
(C) Working Space. Working space about the battery systems shall comply with 110.26. Working clearance shall be measured from the edge of the battery rack.