2.5 UPPER FRESH AIR MAKEUP VENT
The purpose of the fresh air makeup vent is to provide ventilation for commodities that require fresh air circulation. The vent must be closed when transporting frozen foods or controlled atmosphere loads.
Air exchange depends on static pressure differential, which will vary depending on the container and how the container is loaded. The chart below gives air exchange values for an empty container. Higher values can be expected for a fully loaded container.
ZERO EXTERNAL STATIC PRESSURE, 50HZ POWER
AIR |
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FLOW |
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(CMH) |
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225 |
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200 |
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175 |
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150 |
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125 |
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100 |
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75 |
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50 |
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25 |
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0 | 0 | 10 | 20 | 30 | 40 | 50 | 60 | 70 | 80 | 90 | 100 |
PERCENT OPEN
For 60HZ operation multiply air flow values from curve by 1.2
a. Full Open or Closed Positions
Maximum air flow is achieved by loosening the wing nut and rotating the disc to the maximum open position (100% open). The closed position is 0% air flow.
Two slots and a stop are designed into the disc for air flow adjustments. The first slot allows for a 0 to 30% air flow, and the second slot allows for a 30 to 100% air flow. To increase the percentage of air flow, the wing nut must be loosened, and the disc rotated until the desired percentage of air flow matches with the arrow on the disc. Tighten the wing nut. To clear the gap between the slots, loosen the wing nut until the disc clears the stop, and rotate the disc for the second slot.
The operator may also increase or decrease the air flow volume to meet the required air flow by aligning the
arrow on the disc with the percentage of desired air flow marked on the supplied label (see Figure
2.6 LOWER FRESH AIR MAKEUP VENT (Optional)
The purpose of the lower fresh air makeup vent is to provide ventilation for commodities that require fresh air circulation. The vent must be closed when transporting frozen foods.
Air exchange depends on static pressure differential, which will vary depending on the container and how the container is loaded. The chart across gives air exchange values for an empty container. Higher values can be expected for a fully loaded container.
a. Full Open or Closed Positions
The air slide is supplied with two adjustable air control |
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discs. The fresh air makeup can be adjusted for 15, 35, |
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50 and 75 cubic meters per hour (CFM). The air flow has |
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been established at 60 Hz power, and a 2 1/2 inch T bar, |
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2 | ||
with 15 mm (0.6 inch) H2O external static above free | ||
nuts and rotating each disc to the maximum open | SECTION | |
blow. |
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Maximum air flow is achieved by loosening the hex |
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position (100% open). The closed position is 0% air |
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flow. |
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The operator may also adjust the openings to increase or |
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decrease the air flow volume to meet the required air |
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flow. |
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NOTE |
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The main air slide is in the fully closed position |
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during reduced air flow operation. |
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a. Air Sampling for Carbon Dioxide (CO2) Level |
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Loosen hex nuts and move the cover until the arrow on |
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the cover is aligned with the “atmosphere sampling |
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port” label. Tighten the hex nuts and attach a 3/8 hose to |
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the sampling port. |
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If the internal atmosphere content has reached an |
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unacceptable level, the operator may adjust the disc |
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opening to meet the required air flow volume to |
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ventilate the container. |
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