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LEGEND
HPS – High Pressure Switch
LCS – Loss of Charge Switch
Accurater
Arrow indicates direction of flo w
Step 3 — Defrost Control
Defrost Control
The defrost control is used in all R- -410A heat pump models. Its
features include selectable defrost intervals of 30, 60, 90 minutes,
and standard defrost speed up capability. This section describes the
sequence of operation and trouble shooting methods for this
control.
Defrost Sequence
The defrost control is a time/temperature control that has field
selectable settings of 30, 60, and 90 minutes. These represent the
amount of time that must pass after closure of the defrost
thermostat before the defrost sequence begins.
The defrost thermostat senses coil temperature throughout the
heating cycle.
When the coil temperature reaches the defrost
thermostat setting, it will close, which energizes the DFT terminal
and begins the defrost timing sequence. When the DTF has been
energized for the selected time, the defrost cycle begins, and the
control shifts the reversing valve into cooling position, and turns
the outdoor fan off. This shifts hot gas flow into the outdoor coil
HIGH
QC5
KZ
R13 C8
07
09
0L0
08
ALO
C9
C4
QIL
Z2
06
04
A7
R9
D5 D3
C7
JW5
R3 R5 R6
R2
QCB
Y
R W2 Y
SSTZ-8
P1
W3
Fig. 16 - - Interface Fan Board (IFB)
OUTDOOR COIL
HP S
®
Metering De vice
Fig. 17 - - Typical Heat Pump Operation, Heating Mode
LOW
COM
QC4
QC3
KL
DCR
QCR
C
R11
Q1
D2
QC1
Q3
AL2
RL
G1
01
G2
AB A15
C0
F1
Z1
U1
R4
RL4
C3
JWZ
P2
JW3
P4
C
W3 W3 W2 W2 C
JW4
Y2
Y1
W2
G
C R
DH
Y
TXV in Bypass
Position
LCS
Metering
Position
which melts the frost from the coil. The defrost cycle is terminated
when defrost thermostat opens, or automatically after 10 minutes.
20
A09059
INDOOR COIL
C03012
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