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COOLING SYSTEM
The unit has an air-cooled condenser and is factory-charged
with Refrigerant-22.
The compressors are hermetically sealed, internally sprung
and mounted to the base with rubber insulated hold-down bolts.
The compressors also 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 installation has been completed, energize the crankcase
heaters for at least four hours before operating unit. After this
initial warm-up, 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.
NOTE: Prior to each cooling season, the crankcase heaters
must be energized at least 10 hours before system is
put into operation.
COOLING SEQUENCE OF OPERATION
When the thermostat calls for “first-stage” cooling, the low
voltage control circuit from “R” to “G” and “Y1" (wiring
schematic) is completed to energize compressor #1 and blower
motor simultaneously.
When the thermostat calls for “2nd-stage” cooling, the low
voltage control circuit from “R” to “Y2" is completed to energize
compressor #2 and condenser fan motor #2.
After the thermostat is satisfied and opens, all components
likewise stop simultaneously.
The reversing valve is energized thru the “Y1” circuit when the
subbase is in the cooling mode.
The suction line freezestat will cut the compressors out when
the suction line temperature drops below 26
°
F. This is an
automatic reset device.
HEATING SEQUENCE OF OPERATION
The following sequence of operation is based on using a
standard YORK heat pump two-stage heating/two-stage
cooling thermostat/subbase. Economizer (if supplied)
operation is not allowed in the heating mode - however the
minimum position does operate.
FIRST STAGE HEAT
When the thermostat calls for “heating”, the low voltage control
circuit from “R” to “G” and “W1" (wiring schematic) is completed
to energize the compressors, outdoor fan motors and blower
motor (if subbase is set on auto) simultaneously. If the subbase
has the indoor fan set on ”on" the motor will run all of the time.
SECOND STAGE HEAT
If the compressors alone can not satisfy the heating
requirements, second stage heat will energize all the electric
heat (if supplied) thru the “W2" circuit.
NOTE: On 10 ton units with 54KW heaters, only 36KW of
electric heat can be simultaneously energized with
mechanical heating. The full 54KW operates in emer-
gency heat mode only.
BASIC
UNIT
BLOWER
RANGE
(RPM)
MOTOR*
ADJUSTABLE
MOTOR PULLEY
FIXED
BLOWER PULLEY
BELTS
HP
SERVICE
FACTOR
FRAME
SIZE
EFFICIENCY
(%)
PITCH
DIA.
(IN.)
BORE
(IN.)
PITCH
DIA.
(IN.)
BORE
(IN.)
PITCH
LENGTH
(IN.)
DESIG-
NATION
QTY
BCB090
975-1220
1-1/2
2
1.20
56
82.0
3.4 - 4.4
7/8
6.2
1
50.3
A49
1
BCB120
860-1090
2
3
1.20
56
82.0
3.4 - 4.4
7/8
7.0
1
57.3
A56
1
* All motors are 1750 RPM, have solid bases and are inherently protected. These motors can be selected to operate into their service factor because they are located in the moving air,
upstream of any heating device.
TABLE 7 - BLOWER MOTOR AND DRIVE DATA
OPERATION
511.06-N2W
10
Unitary Products Group
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