Carrier WeatherMaker 38YDB Installation Instructions Manual page 19

DEFROST
The dual capacity control logic for defrost function is the standard
time and temperature initiated, time or temperature terminated.
Defrost only occurs at outdoor temperatures less than 50°F. The
control initiates defrost when outdoor coil thermistor is 30°F (±2°)
or less, and selected defrost time (interval) has been accumulated
during unit operation. Termination occurs when coil thermistor
reaches 80°F (±5°) or defrost period reaches a maximum of 10
minutes. Defrost will occur at the compressor capacity that is being
called for. During defrost, unit operates in high or low capacity,
energizes reversing valve O and auxiliary heat W2, and de-
energizes outdoor fan. Upon termination, there is a 20-sec delay in
outdoor fan being energized.
FIELD-INITIATED FORCED DEFROST
By placing a jumper across forced defrost terminals (See Fig. 15)
for a minimum of 5 sec and then removing it, a defrost cycle can
be initiated. The cycle occurs only if outdoor ambient is less than
50°F, regardless of outdoor coil temperature. The cycle terminates
when coil thermistor reaches 80°F (±5°) or defrost period reaches
a maximum of 10 minutes.
COMPRESSOR VOLTAGE FAILURE (6 FLASHES)
The control senses the voltage of the compressor run winding. If
compressor voltage (Vc) is out of range (less than 90v or greater
than 600v), control shuts compressor off for 15 minutes with
outdoor fan running. After 15 minutes (provided there is a call for
Y1 or Y2), control attempts to start compressor. During this time,
a code of 6 flashes appears at control board. If Vc trip occurs 3
consecutive times during a Y1 request, then low capacity operation
is locked out and control responds to Y2 requests until a reset
occurs. If 3 consecutive trips occur in a combination of Yl and Y2
or all Y2 requests, then both low and high capacity operation will
be locked out. The compressor voltage failure (6 flashes) can be
caused by:
• compressor internal overload trip (refer to Table 10 for correct
winding resistance)
• no 208/230 volt power supply to outdoor unit
NON-PROGRAMMABLE
THERMOSTAT FK4/FV4
FAN COIL
MODEL 2S
24 VAC HOT
R
24 VAC COM
C
FAN
G
COOL/HEAT
Y/Y2
STAGE 2
W/W2
HEAT STAGE 3
RVS COOLING
O/W2
COOL/HEAT
Y1
STAGE 1
N/A B
S1
OUTDOOR
SENSOR
S2
CONNECTION
Fig. 14—Typical Solenoid Valve Wiring
40FK
TWO-SPEED
HEAT PUMP
DH
J1 JUMPER
R R
C
C
G
Y/Y2 Y2
W1
J2 JUMPER
W1
W2
O
O
Y1 Y1
• failed compressor contactor(s)
• failure of start relay to pick-up properly.
• improper wiring
PRESSURE SWITCH PROTECTION
The outdoor unit is equipped with high- and low-pressure
switches. If the control senses the opening of the high or low
pressure switch, it will respond as follows:
1. De-energize the compressor hi or low speed contactor.
2. Keep the outdoor fan operating for 15 minutes.
3. Display the appropriate error code on the status light (see
Table 8).
4. After a 15 minute delay, if Yl or Y2 inputs are on and the LPS
or HPS is reset, energize appropriate compressor contactor,
either low or high.
5. If LPS or HPS has not closed after 15 minute delay, outdoor
fan is turned off. If the open switch closes anytime after the
15-minute delay, then resume operation on call for Y1 and/or
Y2.
HEATING VAPOR PRESSURE SWITCH
(PressureGuard™)
This outdoor unit is equipped with a heating vapor pressure
limiting device which cycles the outdoor fan at high ambient
heating conditions. The exact ambient at which outdoor fan cycles
depends on indoor and outdoor unit sizing. The effect of outdoor
fan cycling on HSPF (Heating Seasonal Performance Factor) is
insignificant, due to its occurrence at outdoor ambient where
building load is very low. Puron® is a high-pressure refrigerant.
The purpose of this switch is to provide maximum flexibility and
minimum cost for the installer/owner by not requiring special
thicker wall vapor tubing and indoor coils, thus allowing limited
retrofit. The use of this switch also allows the maximum number
of indoor coil choices at minimum cost for the installer/owner,
since it can use standard refrigerant tubing.
NOTE: Due to the presence of a vapor pressure switch in outdoor
unit fan circuit and the possibility of fan cycling, this unit may go
into brief defrost at high ambient heating conditions.
19
Y1
Y2
LLS
Y2
Y1
A00333