Carrier 50FC 04 Series Service And Maintenance Instructions page 5

lower fan rpms. This offset is factory set and controlled by the
UCB. If fan speed verification is being done with a strobe, fan
speed should be verified in all unit operation modes.
Units with Electro-mechanical controls
The Fan Speed set up controls are located on the lower section
of the Unit Control Board (UCB). See Fig. 7 for location.
1. Check the job specifications for the cfm (cubic feet per
minute) and ESP (external static pressure) required.
2. Using the chart on the Fan Speed Set Up labels (see
Fig. 8), calculate the vdc from the cfm and ESP for the
base unit.
3. If installing any accessories listed at the bottom of the Set
Up Label, add accessory vdc to base unit vdc in upper por-
tion of label. For electric heaters use only one adder (e.g.,
2 stage heater uses only 2 stage adder, not 1 stage plus
2 stage).
NOTE: The Fan Speed Set Up labels are located on the High Volt-
age cover in the Control Box.
4. Connect a multimeter to the vdc terminals on the UCB.
5. Set the Range Switch to either A, B, or C per the Switch
Range table.
6. Using a straight blade screwdriver turn the vdc control dial
to fine tune the vdc reading.
7. Record the reading in the Field Setting field.
Low Speed Fan Adjustment
2-Pin DIP Switch
The Low Speed 2-Pin DIP switch is located near the center of the
UCB. See Fig. 7.
When replacing UCB, the board will be shipped as default without
a low speed selected. To select correct FC low fan speed for 3 to
5 ton 50FC units set both DIP switches to "OFF" (0). For 6 ton
50FC units set both DIP switches "ON" (1). See Table 1. The DIP
switch positions can also be found on the unit's control label
diagram.
Table 1 — Low Speed 2-Pin DIP Switch Settings
LOW SPEED
UNIT SIZE
(tons)
DIP1
3, 4, 5 0
6 1
% OF USER SET
FAN SPEED
DIP2
0 100%
1 66%
Fig. 7 — UCB Fan Speed Controls
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Fan Speed Set Up Controls