Service manual

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,
whichwillvarydependingonthecontainerandhowthe
containeris loaded.Thechartbelowgives airexchange
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 102030405060708090100
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
nutand rotatingthediscto themaximum openposition
(100% open). The closed position is 0% air flow.
Two slots and a stop are designed into the disc for air
flowadjustments.Thefirstslotallowsfora0to30%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
desiredpercentageofairflowmatcheswiththearrowon
thedisc.Tightenthewingnut.Toclearthegapbetween
the slots, loosen the wing nut until the disc clears the
stop, and rotate the disc for the second slot.
The operator mayalso increase or decreasethe airflow
volume to meet the required air flow by aligning the
arrowonthediscwiththepercentageofdesiredairflow
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 i s 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,
whichwillvarydependingonthecontainerandhowthe
containeris loaded.Thechartacrossgivesairexchange
values for an empty container. Higher values can be
expected for a fully loaded container.
a. Full Open or Closed Positions
Theairslideis supplied with two adjustable air control
discs. The fresh air makeup can be adjusted for 15, 35,
50and75cubicmetersperhour(CFM).Theairflowhas
beenestablishedat60Hzpower,anda21/2inchTbar,
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.
Theoperatormayalsoadjusttheopeningstoincreaseor
decrease the air flow volume to meet the required air
flow.
NOTE
Themainairslideisin thefullyclosedposition
during reduced air flow operation.
a. Air Sampling for Carbon Dioxide (CO
2
) Level
Loosenhex nuts and move the cover until the arrowon
the cover is aligned with the “atmosphere sampling
port”label.Tightenthehexnutsandattacha3/8hoseto
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.