IM 178 / Page 29
Preparing Unit for Operation
Moving machinery hazard. May cause severe injury or death.
Disconnect power and lock off before servicing equipment. More than one disconnect may be required to de-energize unit.
Relief Damper Tie-Down
Economizer sections with a 30" or 40" return fan have a relief
damper that is tied down for shipping. Two brackets and two
screws must be removed before operation to allow free
movement of dampers. Access is from inside the economizer
section.
Spring Isolated Fans
1. Open fresh air intake louver door and remove the triangu-
lar shaped floor pan (pan is fastened by sheet metal
screws).
2. Forward spring mount is now visible and can be replaced
if required.
3. Caulk all edges of the floor pan before reinstalling to
prevent leaks.
Figure 25. Fan mounting springs
Table 11. Nominal isolator clearance, fan off
SUPPLY FAN
RETURN FAN
UNIT SIZE
FRONT
BACK
FRONT
BACK
800C
.06"
.75"
.25"
.50"
802C
.18"
.58"
.25"
.50"
Fan Base
Nom. 0.38" Clearance
While Running
Leveling
Bolt
Shipping Hold-down Bolt
(Remove from unit.)
Release of spring mounts
Spring mounted return fans or supply fans have been locked
down for shipment. Using a
9
⁄
16
" hexagon socket, remove the
shipping lock-down bolts from the unit. (The front mounts on
return fans are accessible by removing a 3" O.D. closure plug
in the louvered fresh air intake area. Replace the closure plug
after removing lock-down bolt.) All four bolts on each fan
assembly must be removed.
Adjustment of spring mounts
Each spring mount is also provided with a leveling bolt.
Turning the leveling bolts clockwise with a
15
⁄
16
" socket raises
the fan base; turning the bolts counterclockwise lowers the
fan base. (See Figure 25 for adjustment.)
Moving machinery hazard. May cause severe injury
or death.
The fans must be started for the first time in accordance
with the “Check, Test and Start Procedures” section of
this manual. If this is not done, severe fan damage can
occur.
When the fan is running, there should be a nominal .038"
clearance below for all four spring mounts as shown in Figure
25. Thus, the fan base should ride level when operating
against a static pressure.
When the fan is not running, the fan assembly will tip
forward and no longer be level. The “Nominal Isolator Clear-
ance” table is provided so that leveling bolt adjustment may
be done when the fan is not running. However, some further
adjustment may be required to compensate for variations.
Keep in mind that when the fan is running with doors shut, the
assembly should ride level and the discharge housing should
seal in the fan bulkhead.
Note: If it is necessary to change or replace the forward
(front) isolators on the return fan, proceed as follows:
!
WARNING
!
WARNING
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