Carrier GZ024, Руководство по установке, Страница: 20 / 34

20
SYSTEM FUNCTIONS AND SEQUENCE
OF OPERATION
GZ models utilize either a Communicating Wall Control or a
standard 2--stage heat pump thermostat.
With a call for first stage cooling/heating, the low stage is
energized. If low--stage cannot satisfy the cooling/heating demand,
high stage is energized by the second stage of indoor thermostat.
After second stage is satisfied, the unit returns to low--stage
operation until the first stage is satisfied or until second stage is
required again.
When both first and second stage cooling are satisfied, the
compressor will shut off. When a 2--stage unit is operating at
low--stage, system vapor (suction) pressure will be higher than a
standard single--stage system or high--stage system.
Communicating Sequence
: The UPM board controls all
functions. See Fig. 22.
Non--Communicating Sequence : The reversing valve is energized
to cool.
Cooling -- The first stage of cooling powers Y1 and O. The
second stage of cooling powers Y1, Y2 and O.
Heating
-- The first stage of heating powers Y1, and the second
stage of heating powers Y1 and Y2.
Communication and Status Function Lights
A green LED (COMM light) on the UPM (see Fig. 22) indicates
successful communication with the other system products. The
green LED will remain OFF until communication is established.
Once a valid command is received, the green LED will turn ON
continuously. If no communication is received within 2 minutes,
the LED will be turned OFF until the next valid communication.
Amber Status Light
-- An amber colored STATUS light is used to
display the operation mode and fault codes as specified in the
troubleshooting section. See Table 15 for codes and definitions.
NOTE
: Only one code will be displayed on the UPM board (the
most recent, with the highest priority).
Time Delays
Unit time delays include:
S
Five minute time delay to start cooling or heating operation when
there is a call from the thermostat or user interface. To bypass this
feature, momentarily short and release Timer Speed--Up pins.
S
Five minute compressor re--cycle delay on return from a
brown--out condition.
S
Two minute time delay to return to standby operation from last
valid communication (with UI only).
S
There is no delay between staging from low to high and from high
to low capacity. The compressor will change from low to high
and from high to low capacity “on the fly” to meet the demand.
Compressor Operation
The basic scroll design has been modified with the addition of an
internal unloading mechanism that opens a by--pass port in the first
compression pocket, effectively reducing the displacement of the
scroll. The opening and closing of the by--pass port is controlled by
an internal electrically operated solenoid.
The modulated scroll uses a single step of unloading to go from
full capacity to approximately 67% capacity. A single speed, high
efficiency motor continues to run while the scroll modulates
between the two capacity steps. Modulation is achieved by venting
a portion of the gas in the first suction pocket back to the low side
of the compressor, thereby reducing the effective displacement of
the compressor.
Full capacity is achieved by blocking these vents, thus increasing
the displacement to 100%. A DC solenoid in the compressor
controlled by a rectified 24 volt AC signal in the external solenoid
plug moves the slider ring that covers and uncovers these vents.
The vent covers are arranged in such a manner that the compressor
operates at approximately 67% capacity when the solenoid is not
energized and 100% capacity when the solenoid is energized. The
loading and unloading of the two step scroll is done ”on the fly”
without shutting off the motor between steps.
NOTE : 67% compressor capacity translates to approximately
75% cooling or heating capacity at the indoor coil. The
compressor will always start unloaded and stay unloaded for five
seconds even when the thermostat is calling for high stage capacity.
Safety Devices and UPM Board
3
1
2
4
5
6
8
9
10
12
11
13
14
15
16
17
18 19
7
1. PL2 LPS Low pressure switch
11.
C W 1 Y 1 Y2 0
: Standard tstat
connection
2. PL3 HPS : High pressure switch 12. J2 Speed Up Timer : Test jumper
3. SEC1 and SEC2 : Transformer 13. S1 : DIP Switches
4. VS : Start circuit high volt. 14. PL8 Model : Model plug conn.
5.
L2 and L1
: Contactor and high
voltage
15.
PL6 FRZ1
: Water coil freeze sen-
sor
6. PWM1 and PWM2 : N/A 16. PL6 OPT : N/A
7. F1 : 3 amp fuse 17. PL1 RVS : Reversing valve plug
8. PL5 : Compressor plug 18. LED1 COMM : Comm status light
9. PL7 : ABCD comm. stat conn.
19. LED2 STATUS : Status and fault
code light
10. COND : Condensate overflow
A150170
Fig. 22 -- UPM Board
The UPM Board includes the following features:
S
LOW PRESSURE SWITCH : The low pressure switch safety is
designed to shut down the compressor in th event of loss of
charge. Cut in 60 +/-- 15 psig and cut out 40 +/-- psig.
S
HIGH PRESSURE SWITCH : The high pressure switch safety
is designed to shut down the compressor if it exceeds limits. Cut
in 420 +/-- 15 psig and cut out 600 +/-- psig.
Pressure Switch Protection:
The split geothermal unit is
equipped with high-- and low--pressure switches. If the control
senses the opening of a high-- or low--pressure switch, it will
respond as follows:
1. De--energize the compressor contactor.
2. Display the appropriate fault code (see Table 15).
3. After a 15 minute delay, if there is a call for cooling or heat-
ing and LPS or HPS is reset, the compressor contactor is
energized.
4. If the open switch closes anytime after the 15 minute delay,
then resume operation with a call for cooling or heating.
5. If LPS or HPS trips 2--4 consecutive cycles per the dip
switch lockout setting or UI setting (Communicating only),
the unit operation is locked out for 4 hours.
6. In the event of a high--pressure switch trip or high--pressure
lockout, check the refrigerant charge, and the coax coil (in
cooling) for water issues, or indoor airflow in heating.
7. In the event of a low--pressure switch trip or low--pressure
lockout, check the refrigerant charge and indoor airflow
(cooling) and coax coil water pressure and flow in heating.
S
LOW PRESSURE BYPASS TIMER : If the compressor is
running and the low pressure switch opens, the board will keep
the compressor ON for 120 seconds. After 2 minutes, if the low
pressure switch remains open, the board will shut down the
compressor and enter a soft lockout. The compressor will not be