2-13
T-294-01
2.7 UPPER FRESH AIR MAKEUP VENT
The purpose of the upper 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 below gives air exchange
values for an empty container. Higher values can be
expected for a fully loaded container.
0
25
50
75
100
125
150
175
200
225
0
10 20 30 40 50 60 70 80 90 100
AIR
FLOW
(CMH)
2-3/8
”
PERCENT OPEN
T-BAR
ZERO EXTERNAL STATIC PRESSURE,
50HZ POWER
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 2-1).
2.8 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
discs. The fresh air makeup can be adjusted for 15, 35,
50 and 75 cubic meters per hour (CFM). The air flow has
been established at 60 Hz power, and a 2 1/2 inch T bar,
with 15 mm (0.6 inch) H
2
O external static above free
blow.
Maximum air flow is achieved by loosening the hex
nuts and rotating each disc to the maximum open
position (100% open). The closed position is 0% air
flow.
The operator may also adjust the openings to increase or
decrease the air flow volume to meet the required air
flow.
NOTE
The main air slide is in the fully closed position
during reduced air flow operation.
a. Air Sampling for Carbon Dioxide (CO
2
) Level
Loosen hex nuts and move the cover until the arrow on
the cover is aligned with the “atmosphere sampling
port” label. Tighten the hex nuts and attach a 3/8 hose to
the sampling port.
If the internal atmosphere content has reached an
unacceptable level, the operator may adjust the disc
opening to meet the required air flow volume to
ventilate the container.
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