York SUNLINE 2000 D3CE 036 Installation Instruction Download Page 13

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Two-Stage Cooling:
A two-stage cooling thermostat may be used if the unit has an
economizer. First-stage cooling is provided by the economizer
if the outdoor air enthalpy is acceptable, and second-stage
cooling is provided by the compressor. Jumper wire J1 must
be removed. Refer to unit wiring diagram.

After the thermostat is satisfied and opens, the blower
continues to run for a short time. All other components stop.

SAFETY CONTROLS

The refrigerant system is equipped with the following safety
controls:

1. A Suction Line Freezestat to protect against low evaporator

temperatures due to a low air flow or a low return air
temperature.

2. A High Pressure Cutout Switch to protect against excessive

discharge pressures due to a blocked condenser coil or a
condenser motor failure.

3. A Low Pressure Switch to protect against loss of refrigerant

charge.

If any of the above safety controls opens, the refrigerant system
is locked out. The lock out of the system can be reset by
opening the 24V circuit either at the room thermostat or at the
unit disconnect.

HEATING SEQUENCE OF OPERATION

The following sequence of operation is based on using a
standard single-stage or two-stage heating thermostat.

WITH POWER TO UNIT AND THERMOSTAT IN THE
HEATING MODE
Single-Stage Heating:

a. If the fan switch is in the “ON” position, the evaporator

blower motor relay (BR) will be energized through terminal
G to provide continuous blower operation. If the fan switch
is in the “AUTO” position, the blower operates only when
there is a call for heating by the thermostat.

b. Upon a call for heat by the thermostat, the first stage of heat

is energized. Sequencer 1S (or contactor 2M) is always the
first and last to complete its timing cycle and controls power
to the evaporator blower motor.

c. The thermostat cycles the electric heat to satisfy the heat-

ing requirements of the conditioned space.

Two-Stage Heating:

a. If the fan switch is in the “ON” position, the evaporator

blower motor relay (BR) is energized through terminal G
to provide continuous blower operation. If the fan switch is
in the “AUTO” position, the blower operates only when there
is a call for heating by the thermostat.

b. Upon a call for first-stage heat by the thermostat, the first

stage of heat is energized.

If the thermostat calls for the second stage of heat, the
second stage of heat is energized.

As before, sequencer 1S (or contactor 2M) maintains
control of the evaporator blower.

c. The thermostat cycles the electric heat to satisfy the

heating requirements of the conditioned space.

CONTINUOUS BLOWER - Continuous blower operation is
possible by closing the R to G circuit on the thermostat.

HEAT ANTICIPATOR SETPOINTS

It is important that the anticipator setpoint be correct. Too high
a setting results in longer heat cycles and a greater
temperature swing in the conditioned space. Reducing the
value below the correct setpoint causes shorter “ON” cycles
and may result in the lowering of the temperature within the
conditioned space. Refer to Table 8 for the required heat
anticipator setting.

CHECKING SUPPLY AIRFLOW

The speed of the supply air blower depends on the required
airflow, the unit accessories and the static resistances of both
the supply and the return air duct systems. With this
information, the speed for the supply air blower can be
determined from the static resistance and blower performance
data on Tables 3, 4 and 5.

Knowing the required blower RPM and the blower motor HP,
the speed setting for the direct-drive supply air motor can be
determined.

The setting (turns open) for the optional belt-drive supply air
motor pulley can be determined from Table 9.

OPTIONAL BELT-DRIVE BLOWER

All units with belt-drive blowers have single-speed motors. The
variable pitch pulley on the blower motor can be adjusted to
obtain the desired supply air airflow. Refer to Table 6 for blower
motor and drive data.

Start the supply air blower motor. Adjust the resistances in both
the supply and the return air duct systems to balance the air
distribution throughout the conditioned space. The job
specifications may require that this balancing be done by
someone other than the equipment installer.

To check the supply airflow after the initial balancing has been
completed:

1. Remove the dot plugs from the holes in the filter access and

blower access panels. See Figure 5 for location of plugs.

2. Insert at least 203mm (8 in.) of 6mm (

⁄

in.) tubing into each

of these holes for sufficient penetration into the air flow on
both sides of the evaporator coil.

NOMINAL

HEATER

SIZE

VOLTAGE

SETTING, AMPS