York D2CG300 User Manual
COOLING SYSTEM
The cooling section is a complete factory package utilizing an
air-cooled condenser. The system is factory-charged with
Refrigerant-22.
The compressors are hermetically sealed, internally sprung
and base-mounted with rubber-insulated hold-down bolts.
Compressors have inherent (internal) protection. If there is an
abnormal temperature rise in a compressor, the protector will
open to shut down the compressor.
air-cooled condenser. The system is factory-charged with
Refrigerant-22.
The compressors are hermetically sealed, internally sprung
and base-mounted with rubber-insulated hold-down bolts.
Compressors have inherent (internal) protection. If there is an
abnormal temperature rise in a compressor, the protector will
open to shut down the compressor.
PRELIMINARY OPERATION COOLING
After the initial installation, the compressors should be given
three false starts (energized just long enough to make a few
revolutions) with 5-7 minutes delay between each start, before
being put into full time service.
three false starts (energized just long enough to make a few
revolutions) with 5-7 minutes delay between each start, before
being put into full time service.
COOLING SEQUENCE OF OPERATION
NO OUTDOOR AIR OPTIONS - When the room thermostat
calls for “first-stage” cooling, the low voltage control circuit from
“R” to “G” and “Y1" is completed to energize compressors #1/2
(50% capacity), condenser fan motor #1, and the supply air
blower motor (if the fan switch on the room thermostat is set in
the ”AUTO" position).
When the thermostat calls for “second-stage” cooling, the low
voltage control circuit from “R” to “Y2" is completed to energize
compressor #3/4.
After the thermostat is satisfied and opens, all components will
stop simultaneously. The blower motor will continue to operate
if the fan switch on the room thermostat is set in the “ON”
position.
ECONOMIZER WITH SINGLE ENTHALPY SENSOR - When
the room thermostat calls for “first-stage” cooling, the low
voltage control circuit from “R” to “G” and “Y1" is completed.
The ”R" to “G” circuit energizes the blower motor (if the fan
switch on the room thermostat is set in the “AUTO” position)
and drives the economizer dampers from fully closed to their
minimum position. If the enthalpy of the outdoor air is below the
setpoint of the enthalpy controller (previously determined), “Y1"
energizes the economizer. The dampers will modulate to
maintain a constant supply air temperature as monitored by the
discharge air sensor. If the outdoor air enthalpy is above the
setpoint, ”Y1" energizes compressors #1/2, and condenser fan
motor #1.
When the thermostat calls for “second-stage” cooling, the low
voltage control circuit from “R” to “Y2" is completed. If the
enthalpy of the outdoor air is below the setpoint of the enthalpy
controller (i.e. first stage has energized the economizer), ”Y2"
will energize compressors #1/2. If the outdoor air is above the
setpoint, “Y2" will energize compressor #3/4.
After the thermostat is satisfied and opens, all components will
stop simultaneously. The blower motor will continue to operate
if the fan switch on the room thermostat is set in the “ON”
position.
ECONOMIZER WITH DUAL ENTHALPY SENSORS - The
operation with the dual enthalpy sensors is identical to the
single sensor except that a second enthalpy sensor is mounted
in the return air. This return air sensor allows the economizer
to choose between outdoor air and return air, whichever has
the lowest enthalpy value, to provide maximum operating
efficiency.
ECONOM IZ ER ( S INGLE OR DUAL) WITH POWER
EXHAUST - This system operates as specified above with one
calls for “first-stage” cooling, the low voltage control circuit from
“R” to “G” and “Y1" is completed to energize compressors #1/2
(50% capacity), condenser fan motor #1, and the supply air
blower motor (if the fan switch on the room thermostat is set in
the ”AUTO" position).
When the thermostat calls for “second-stage” cooling, the low
voltage control circuit from “R” to “Y2" is completed to energize
compressor #3/4.
After the thermostat is satisfied and opens, all components will
stop simultaneously. The blower motor will continue to operate
if the fan switch on the room thermostat is set in the “ON”
position.
ECONOMIZER WITH SINGLE ENTHALPY SENSOR - When
the room thermostat calls for “first-stage” cooling, the low
voltage control circuit from “R” to “G” and “Y1" is completed.
The ”R" to “G” circuit energizes the blower motor (if the fan
switch on the room thermostat is set in the “AUTO” position)
and drives the economizer dampers from fully closed to their
minimum position. If the enthalpy of the outdoor air is below the
setpoint of the enthalpy controller (previously determined), “Y1"
energizes the economizer. The dampers will modulate to
maintain a constant supply air temperature as monitored by the
discharge air sensor. If the outdoor air enthalpy is above the
setpoint, ”Y1" energizes compressors #1/2, and condenser fan
motor #1.
When the thermostat calls for “second-stage” cooling, the low
voltage control circuit from “R” to “Y2" is completed. If the
enthalpy of the outdoor air is below the setpoint of the enthalpy
controller (i.e. first stage has energized the economizer), ”Y2"
will energize compressors #1/2. If the outdoor air is above the
setpoint, “Y2" will energize compressor #3/4.
After the thermostat is satisfied and opens, all components will
stop simultaneously. The blower motor will continue to operate
if the fan switch on the room thermostat is set in the “ON”
position.
ECONOMIZER WITH DUAL ENTHALPY SENSORS - The
operation with the dual enthalpy sensors is identical to the
single sensor except that a second enthalpy sensor is mounted
in the return air. This return air sensor allows the economizer
to choose between outdoor air and return air, whichever has
the lowest enthalpy value, to provide maximum operating
efficiency.
ECONOM IZ ER ( S INGLE OR DUAL) WITH POWER
EXHAUST - This system operates as specified above with one
addition. The power exhaust motor is energized whenever the
economizer is chosen by the enthalpy sensor for first stage
cooling, “Y1". As always, the ”R" to “G” connection provides
minimum position but does not provide power exhaust
operation.
MOTORIZED OUTDOOR AIR DAMPERS - This system
operation is the same as the units with no outdoor air options
with one exception. When the “R” to “G” circuit is complete, the
motorized damper drives open to a position set by the damper
motor adjustment. When the “R” to “G” circuit is opened, the
damper spring returns fully closed.
CONTINUOUS BLOWER - Continuous blower operation is
possible by closing the R to G circuit on the thermostat.
economizer is chosen by the enthalpy sensor for first stage
cooling, “Y1". As always, the ”R" to “G” connection provides
minimum position but does not provide power exhaust
operation.
MOTORIZED OUTDOOR AIR DAMPERS - This system
operation is the same as the units with no outdoor air options
with one exception. When the “R” to “G” circuit is complete, the
motorized damper drives open to a position set by the damper
motor adjustment. When the “R” to “G” circuit is opened, the
damper spring returns fully closed.
CONTINUOUS BLOWER - Continuous blower operation is
possible by closing the R to G circuit on the thermostat.
SAFETY CONTROLS
Each refrigerant system is equipped with the following safety
controls:
controls:
1. A Suction Line Freezestat to protect against low evaporator
temperatures due to a low air flow or a low return air
temperature. (Opens at 26
temperature. (Opens at 26
°
F + 5
°
F and resets at 38
°
F +
5
°
F)
2. A High Pressure Cutout Switch to protect against excessive
discharge pressures due to a blocked condenser coil or a
condenser motor failure. (Opens at 380 psig + 10 and resets
at 300 psig +10)
condenser motor failure. (Opens at 380 psig + 10 and resets
at 300 psig +10)
3. A Low Pressure Switch/Loss Of Charge to protect against
loss of refrigerant charge. (Opens at 7 psig + 3 and resets
at 22 psig + 5)
at 22 psig + 5)
If either one of the above safety controls opens, that individual
refrigerant system will be locked out. The other refrigerant
system will continue in operation unless it too is effected by the
same fault. The lock out of either system can be reset by
opening the 24V circuit either at the room thermostat or at the
unit disconnect.
refrigerant system will be locked out. The other refrigerant
system will continue in operation unless it too is effected by the
same fault. The lock out of either system can be reset by
opening the 24V circuit either at the room thermostat or at the
unit disconnect.
ELECTRIC HEATING - SEQUENCE OF OPERATION
WITH POWER TO UNIT AND THERMOSTAT IN THE
HEATING MODE
Single-stage heating: (applies only to 18 KW heater, all other
heaters MUST use a two-stage thermostat:)
HEATING MODE
Single-stage heating: (applies only to 18 KW heater, all other
heaters MUST use a two-stage thermostat:)
a) If the fan switch is in the “ON” position, the evaporator
blower motor contactor (3M) will be energized through
terminal G to provide continuous blower operation. If the fan
switch is in the “AUTO” position, the blower will operate only
when there is a call for heating by the thermostat.
terminal G to provide continuous blower operation. If the fan
switch is in the “AUTO” position, the blower will operate only
when there is a call for heating by the thermostat.
NOTE: All 240 & 480V heaters are provided with manual
reset backup protection limits. These will de-ener-
gize the heaters should the primary limit fail to open
or the contactors fail to open in a failure mode.
gize the heaters should the primary limit fail to open
or the contactors fail to open in a failure mode.
b) Upon a call for heat by the thermostat, the heater contactor
(6M) will be energized.
c) The thermostat will cycle the electric heat to satisfy the
heating requirements of the conditioned space.
Two-stage heating: (applies to all heaters except 18 KW):
a) If the fan switch is in the “ON” position, the evaporator
blower motor contactor (3M) will be energized through
terminal G to provide continuous blower operation. If the fan
terminal G to provide continuous blower operation. If the fan
OPERATION
530.18-N11Y
Unitary Products Group
15