Air Flow Adjustments; Belt Drive Models Only - Daikin DBC Series Installation Instructions Manual

Three Phase Models Only
Control Voltage Check
Close the disconnect switch to energize control
transformer. Check primary and secondary (24V) of control
transformer.

AIR FLOW ADJUSTMENTS

NOTE: For 2 Speed Models, airflow adjustments
must be made on high speed, i.e., 2nd stage cooling
or in heat mode.
The drive on the supply fan is typically set in the middle of
the RPM range. The drive motor sheave pitch diameter is
field adjustable for the required airflow. Upon completion
of the air flow balancing, we recommend replacing the
variable pitched motor sheave with a properly-sized fixed
sheave. A matching fixed sheave will provide longer belt
and bearing life and vibration free operation. Initially, it
is best to have a variable pitched motor sheave for the
purpose of airflow balancing, but once the balance has
been achieved, fixed sheaves maintain alignment and
minimize vibration more effectively. Refer to the following
"Drive Adjustments" section.
When the final adjustments are complete, the current
draw of the motor should be checked and compared to
the full load current rating of the motor. The amperage
must not exceed the service factor stamped on the motor
nameplate.
If an economizer is installed, check the unit operating
balance with the economizer at full outside air and at
minimum outside air. Upon completion of the air flow
balancing, we recommend replacing the variable pitched
motor sheave with a properly-sized fixed sheave. A
matching fixed sheave will provide longer belt and bearing
life and vibration free operation. Initially, it is best to have
a variable pitched motor sheave for the purpose of airflow
balancing, but once the balance has been achieved, fixed
sheaves maintain alignment and minimize vibration more
effectively.
NOTE: Never run high stage CFM below 300
CFM per ton, evaporator freezing or poor unit
performance is possible.
Evaporator Fan Rotation Check
Check that fan rotates clockwise when viewed from the
drive side of unit and in accordance with rotation arrow
shown on blower housing. If it does not, reverse any two
incoming power cables at Single Point Power Block. In this
case, repeat bearing check.
Do not attempt to change load side wiring. Internal wiring
assures all motors and compressors will rotate in correct
direction once evaporator fan motor rotation check has
been made.
Electrical Input Check
Make preliminary check of evaporator fan ampere draw
and verify that motor nameplate amps are not exceeded. A
final check of amp draw should be made upon completion
of air balancing of the duct system.
Set Evaporator Fan Rpm
Actual RPM's must be set and verified with a tachometer
or strobe light. Refer to Appendex A for basic unit fan
RPM. Refer also to "Airflow" section of this manual. With
disconnect switch open, disconnect thermostat wires
from terminals Y and W. This will prevent heating and
mechanical cooling from coming on. Place a jumper wire
across terminals R and G at TB1 terminal block. Close
disconnect switch; evaporator fan motor will operate so
RPM can be checked.

BELT DRIVE MODELS ONLY

Refer to "Motor Sheave Adjustments" section.
Bearing Check
Prior to energizing any fans, check and make sure that all
setscrews are tight so that bearings are properly secured
to shafts.
Tension and Alignment Adjustment
Correct belt tension is very important to the life of your belt.
Too loose a belt will shorten its life; too tight, premature
motor and bearing failure will occur. Check your belt
drive for adequate "run-in" belt tension by measuring the
force required to deflect the belt at the midpoint of the
span length. Belt tension force can be measured using
a belt tension gauge, available through most belt drive
manufacturers.
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