ACH = QA  x 60 /Room Volume (4)

Example。 Per manufacturer specification, one fully charged lead calcium cell, at 77 degrees F (25 degrees C), will pass 0。24 amperes of charging current for every 100 ampere-hour cell capacity, measured at the 8-hour rate, when subject to an equalizing potential of 2。33 volts。 Calculate the required rate of ventilation for a battery bank consisting of 182 cells。 Each cell has a nominal 1,360-amphere hours capacity at the 8- hour rate and being equalized at an electrolyte temperature of 92 degrees F (30 degrees C)。

At 92 degrees F (30 degrees C), FC is doubled FC = 0。24 amp x 2 = 0。48 amp

AH = 1360 amp hr

K = 0。016 ft3/amp hr cell

C  0。48 amp 100 amp hr

  ft3

x 1360 amp hr x 0。016

amp hr cell

ft3

x 182 cell 19

hr

ft3

19

 1 hr

3

Q  hr 60 min 32 0。01

ft

min

(5)

Assume a room size of 8,000 cubic feet (226。5 cubic meters) with a safety factor of k = 2, charging 3 banks of battery。

ft3

QA 32

min

x 3 x 2 192

ft3 min

ACH 192

ft3 60 min   1AC AC x x 1。44

(6)

min

hr 8000 ft3 hr

8-3。2 Ductwork。  Design ductwork in accordance with paragraph 2-4。1。 Use FRP or PVC ductwork。

8-3。3 Fans and Motors。  Select fans in accordance with paragraph 2-4。2。 Use AMCA 201, Type B spark resistant construction and explosion proof motors。 Fans must have non-sparking wheel。 Locate the motor outside of the air stream。

8-3。4 Weather Stack Design and Location。  Avoid re-entry of exhaust air by discharging the exhaust high above the roof line or by assuring that no window, outdoor intakes, or other such openings are located near the exhaust discharge。 See paragraph 2-4。3 for additional considerations。

8-3。5 Air Cleaning Device。  Due to the quantities and types of contaminants generated by this process, there is no requirement for air pollution control equipment。

8-3。6 Replacement Air。 Design a replacement air system in accordance with paragraph 2-4。5。 Design the replacement air volumetric flow rate for approximately 95 percent of the exhaust airflow rate to provide a negative pressure inside the maintenance facility。 Use 100 percent outside air。 Do not re-circulate exhaust air back to the maintenance facility。

8-3。7 System Controls。  Design system control in accordance with paragraph 2-5 and the following criteria:

a。 Interlock the charging circuit and the exhaust fan in the shop to ensure chargers will not operate without ventilation。