Daikin DBG Series Service Instructions Manual page 17

SYSTEM OPERATION
Pre-startup Precautions
Transformer and Induced Draft Motor
NOTE: On the 208/230 volt units only.
Ensure the transformer and induced draft motor are set on
the appropriate voltage taps. Both the transformer tap and
induced draft motor are set on 230v from the factory. To
change transformer and induced draft motor voltage to 208V,
move the black wire on the transformer from the 230V tap
to the 208V tap.
It is important to your safety that the unit has been properly
grounded during installation. Check ground lug connection in
main control box for tightness prior to closing circuit breaker
or disconnect switch. Verify that supply voltage on line side
of disconnect agrees with voltage on unit identification plate.
System Voltage - That nominal voltage value assigned to a
circuit or system for the purpose of designating its voltage class.
Nameplate Voltage - That voltage assigned to a piece of
equipment for the purpose of designating its voltage class
and for the purpose of defining the minimum and maximum
voltage at which the equipment will operate.
AIR FLOW ADJUSTMENTS
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. The
total airflow must not be less than that required for operation
of the electric heaters or the furnace.
If an economizer is installed, check the unit operating bal-
ance with the economizer at full outside air and at minimum
outside air.
NOTE:Airflow setting below 300 CFM/Ton is not recommend-
ed, as evaporator freezing or poor unit performance is pos-
sible.Start-up Procedure and Checklist for 2 Speed Models.
Set Evaporator Fan Rpm
Actual RPM's must be set and verified with a tachometer
or strobe light. 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.
For gas heat units, the airflow must be adjusted so that the
air temperature rise falls within the ranges given stated on
Data Plate.
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.
2 SPEED MODELS
NOTE: For 2 Speed Models, airflow adjustments must
be made with the evaporator motor operating at high
speed,i.e, 2nd stage cooling or in heat mode.
BELT DRIVE MODELS ONLY
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 re-
placing 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. For direct drive units, move fan speed wire.
Start-up Procedure and Checklist for 2 Speed
Models:
Models with a V in the 11th position of the model number.
For 2 speed models, the indoor blower will operate on low
speed when in "Fan Only" mode or while in first stage "Cooling"
mode. Unit will operate on high speed in "Heating" mode and
while in second stage "Cooling" mode.
The start-up procedure is the same as for "Air Conditioning
Start-up Procedure" with the understanding that in Step 6,
the indoor blower will run at low speed (~1175 motor rpm)
and in Step 7, the indoor blower will operate at high speed
(~1775 motor rpm).
NOTE: While in the Cooling Mode, to prevent frost from
forming on the evaporator while the unit is operating in
outdoor temperatures of 65°F or lower, it is recommended
that a low ambient kit (LAKT-**) is used. This is strongly
recommended for 2 Speed models due to the lower airflow
while in the first stage cooling. To further protect the
compressor from damage during low ambient conditions,
a Freezestat Kit (FSK***) can be added that turns the
compressor off when the evaporator temperature drops too
low.
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