System Start-up
90 RT-SVX35H-EN
Economizer Damper Adjustment
Exhaust Air Dampers
With the unit "Off", verify that the exhaust dampers (if
equipped) close tightly when the unit is off. Adjust the
damper linkage as necessary to ensure proper closure. An
access panel is provided under each damper assembly.
Fresh Air & Return Air Damper Operation
The fresh air and return air damper linkage is accessible
from the filter section of the unit. The damper linkage
co
nnecting the fresh air dampers to the return air dampers
is preset from the factory in the number 1 position. Refer
to Table 31, p. 91 for the appropriate linkage position for
the unit and operating airflow (cfm).
Arbitrarily adjusting the fresh air dampers to open fully
when the return air dampers are closed or; failing to
maintain the return air pressure dro
p with the fresh air
d
ampers when the return air dampers are closed, can
overload the supply fan motor and cause building
pressurization control problems due to improper cfm
being delivered to the space.
The fresh air/return air damper linkage is connected to a
crank arm with a series of holes that allows the installer or
operator to modify the amount of fresh air damper travel
in order to match t
he return static pressure. Refer to
T
able 31 for the equivalent return air duct losses that
correspond to each of the holes illustrated in Figure 49,
p. 93.
To Adjust the Fresh Air Damper Travel:
1. Drill a 1/4" hole through the unit casing up stream of
the return air dampers. Use a location that will produce
an accurate reading with the least amount of
turbulence. Several locations may be necessary, an
d
average th
e reading.
.
Table 30. 50% exhaust fan drive selections (casings 2-9)
Casing
Size
3 HP 5 HP 7½ HP 15 HP
RPM Drive No RPM Drive No RPM Drive No RPM Drive No
2
500 5
600 6
700 7
800 8
900 9
3
500 5 800 8
600 6 900 9
700 7 1000 A
800 8
900 9
4 & 5
500 5 600 6
600 6 700 7
700 7
6
400 4 700 7
500 5
600 6
9
500 5
600 6
700 7
800 8
WARNING
Reinforce base sheet metal surface!
Do NOT walk on the base sheet metal surface before it
has been reinforced. Bridging between the unit's main
supports may consist of multiple 2 by 12 boards or
sheet metal grating. Failure to comply could result in
death or serious injury.
WARNING
Hazardous Voltage!
HIGH VOLTAGE IS PRESENT AT TERMINAL BLOCK 1TB1
OR UNIT DISCONNECT SWITCH 1S14. Disconnect all
electric power, including remote disconnects before
servicing. Follow proper lockout/tagout procedures to
ensure the power can not be inadvertently energized.
Failure to disconnect power before servicing could
result in death or serious injury.
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