5–3 T-340
Figure 5.2 Upper Fresh Air Make Up Flow Chart
5.3.2 Lower Fresh Air Makeup Vent
a. Full Open or Closed Positions
Maximum air flow is achieved by loosening the wing nuts and moving the cover to the maximum open position
(100% position). The closed position is 0% air flow position. The operator may also adjust the opening to increase
or decrease the air flow volume to meet the required air flow.
b. Reduced Flow for Lower Fresh Air Makeup
NOTE
In order to prevent inaccurate display readings on units equipped with a Vent Position Sensor (VPS),
ensure that the rack and pinion drive of the VPS is not disrupted when adjusting the air makeup vent.
NOTE
Do not loosen the hex nut beyond its stop. Doing so may cause inaccurate display readings and errors in
DataCORDER reports.
Similar to the Upper Fresh Air Makeup vent, two slots and a stop are designed into the Lower Fresh Air slide for air
flow adjustments. The first slot allows for a 0 to 25% air flow; the second slot allows for a 25 to 100% air flow. To
adjust the percentage of air flow, loosen the hex nut and rotate the disc until the desired percentage of air flow
matches with the arrow. Tighten the hex nut. To clear the gap between the slots, loosen the hex nut until the disc
clears the stop.
0
50
100
150
200
250
0 102030405060708090
100
TBAR
1 1/2”
TBAR
2 5/8”
TBAR 3”
AIR
FLOW
(CMH)
50HZ
PERCENT OPEN
0
50
100
150
200
250
300
0 102030405060708090
100
TBAR
1 1/2”
TBAR
2 5/8”
TBAR 3”
AIR
FLOW
(CMH)
60HZ
PERCENT OPEN
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