Defrost Control - Trane 4TWB4018G Installer's Manual

*AM4 & GAM5 Air Handler
Hook-up Diagram
Comfort Control
X2
White W
White
Green G Green
Yellow
Yellow Y
Orange
Orange O
Red
Red R
Blue
Blue
B
Field wiring

11.3 Defrost Control

Defrost controls have a selectable termination temperature. As shipped, defrost will terminate at 47°F. For a
higher termination temperature, cut Jumper J2 to achieve 70°F when at or below 30°F ambient. See Service
Facts shipped in the outdoor unit for more information.
Pin Identification (See Illustration at right)
1. TEST_COMMON (Shorting any of the other pins to this pin causes the function of the other pin to be
executed. Leaving this pin open results in the normal mode of operation.)
2. TST = Test (Shorting TEST_COMMON to this pin speeds up all defrost board timings.)
3. FRC_DFT = Forced Defrost (Short TEST_COMMON to this pin for two (2) seconds to initiate a forced
defrost. Remove the short after defrost initiates.)
Defrost Control Checkout
Normal operation requires:
•
LED on board flashing 1 time/second.
•
24V AC between R & B.
•
24V AC between Y & B with unit operating.
•
Defrost initiation when FRC_DFT pin is shorted to TEST_COMMON pin.
If a defrost control problem is suspected, refer to the service information in control box.
Defrost Termination Temperatures
Outdoor
Temperature
As >22°F
Shipped
10°F–22°F
6°F–10°F
Cut >30°F
Jumper 2
6°F–30°F
All < 6°F
18-BC77D1-6
Air Handler
W3
W2
W1 - White
W1
G
YI (In)
O ** O - Orange
R ** R - Red
B B - Blue
YO (Out)
Y - Yellow
Termination
Temperature
47°F
ODT + 25°F
35°F
47°F
70°F
12 min. or 35°F
every 3 hrs.
Heat Pump
Black
(X2)
Orange
Red
Blue
Defrost Board
Detail
JUMPER 2
TEST PINS
1. * For multiple stages of
electric heat, jumper W1,
W2, and W3 together if
comfort control has only
one stage of heat.
2. ** R to O jumper must be
removed for heat pump
system.
3. Yi and Yo connections
must be made as shown
for freeze protection and
internally mounted con-
densate overflow circuits
Yellow
to work properly.
4. Internally mounted con-
densate switch is optional
and must be ordered
separately.
5. If 3rd party condensate
overflow switches are
installed, they should be
wired in series between
YO and Y to the outdoor
unit.
* T or A
J1
J2
J3
FRC_DFT U1
TST
15