515.28-N3Y
Unitary Products Group
11
WITH POWER TO UNIT AND THERMOSTAT IN
HEATING
POSITION
1.
Reversing valve is de-energized to position refrigerant
circuit for heating operation. In the heating cycle, dis-
charge gas is pumped to the indoor coil which is the con-
denser. The outdoor coil is the evaporator.
2.
If fan switch is in "ON" position, a circuit is made through
blower relay to provide continuous blower operation.
3.
Solid state YORKGUARD V starts time delay period.
After 5 minutes, the system is ready for operation.
4.
When thermostat first stage heating contact closes, a cir-
cuit is made though the YORKGUARD V to energize
contactor and start the system. With fan switch in
"AUTO" position, a circuit is made from thermostat "Y"
contact through blower relay to provide blower operation.
5.
System will cycle with thermostat demand to provide
heating as needed.
6.
After the system has stopped from a heating cycle or
power interruption, the YORKGUARD V will not permit
the system to re-start for 5 minutes. (This protects com-
pressor by allowing system pressures to equalize.)
7.
YORKGUARD V monitors system operation and will
lockout the outdoor unit if it detects a malfunction. When
a lockout occurs, the emergency heat light will flash at
the thermostat. In addition, the fault indicator light on
YORKGUARD V will flash and will continue flashing until
reset even if the lockout was cleared at the thermostat. It
can only be reset by shorting the "test" terminals on
Yorkguard V terminal block for 3 seconds and releasing.
The lights will flash the code, separated by a pause, indi-
cating the failure mode shown in Table 3.
8.
To restore operation after a lockout (if control causing
lockout has automatically reset);
a.
Turn the system switch on the thermostat to the
"OFF" position and return it to the cooling position,
within 5 seconds with a demand for cooling. (OR)
b.
Interrupt the line power or the 24 volt control circuit
power to the indoor unit for 4 seconds.
NOTE:
9.Either of the above methods will start the 5-minute
time delay which may be bypassed by temporarily short-
ing the test terminals for 3 seconds.
OPERATION BELOW LOW-TEMPERATURE CUT-OFF
1.
At an outdoor temperature below the cut-off point, the
compressor operation cannot be justified due to small
amount of heat generated.
2.
YORKGUARD senses this and performs the following
functions:
a.
De-energizes compressor circuit.
b.
Changes the first step of supplemental heat so that
it is controlled by the first stage of the thermostat
along with the fan.
c.
Energizes standby heat (if installed) under control of
second stage of heating thermostat.
OPERATION IN EMERGENCY HEAT POSITION
When switch on thermostat is placed in emergency heat posi-
tion:
1.
Emergency light is energized.
2.
Compressor circuit is locked out.
3.
Supplemental and standby heaters (if installed) will be
controlled by first stage of heating thermostat.
4.
Indoor blower will operate on demand for heat and cycle
off with the last heater element when in "AUTO" position.
SUPPLEMENTAL ELECTRIC HEAT
Supplemental electric heaters are energized by second stage
of heating thermostat. YORKGUARD V will permit operation
of supplemental heaters below balance point. At all outdoor
temperatures above balance point, supplemental heaters are
not permitted to operate.
OPERATION BELOW BALANCE POINT: With second stage
of heating thermostat contact closed, a circuit is made
through YORKGUARD V to energize the supplemental heat-
ers.
When second stage of heating thermostat becomes satisfied,
contact will open to de-energize supplemental heaters.
FOSSIL FUEL OPERATION
NOTE:
Requires the use of the 2AC02700801 kit.
Supplemental gas or oil furnaces are energized by second
stage of heating thermostat. Yorkguard V will permit opera-
tion of supplemental furnace below balance point. At all out-
door temperatures above balance point, supplemental
furnace is not permitted to operate.
OPERATION BELOW BALANCE POINT: With second stage
of heating thermostat contact closed, a circuit is made
through Yorkguard V to energize the supplemental furnace.
When second stage of heating thermostat becomes satisfied,
contact will open to de-energize supplemental furnace.
DEFROST CYCLE
Frost and ice which forms on the outdoor coil during the heat-
ing cycle must be defrosted when it blocks the air flow
through the coil.
Due to the arrangement of the refrigerant circuit within the out-
door coil of these units, frost may accumulate unevenly in dif-
ferent sections of the coil. However, a normal defrost may
occur even though the coil is not completely covered with frost.
