Carrier 40RFAA12 - Three Stage Operation

17
THREE STAGE OPERATION
All units are factory shipped for 2-stage cooling operation. To con-
vert a unit to 3-stage operation, see Fig. 17 and adjust the follow-
ing wires between the control board and two terminal strips on the
side of the control box:
1. Remove gray wire at Thermostat CB terminal X and insulate.
2. Move orange wire from Thermostat CB terminal Y2 to
terminal X.
3. Make connections of blue wire included in factory harness.
Connect one end to Thermostat CB terminal Y2 and the other
to Indoor Connection Board terminal Y2.
4. Move orange wire from Indoor Connection Board terminal
Y2 to terminal X.
The 3-stage system will run the fan at low speed with a G, Y1, and
Y1+Y2 call, and at high speed with a call for Y1, Y2, and Y3.
A thermostat with 3 cooling stage capability is required for this
system configuration.
Fig. 17 — Three Stage Wiring
DDC
TSTAT
Y1
Y2
X
Y1
Y2
X
UCB
COMP
BLU
BLU
BLU
BLU
ORN
BLU
ORN
ORN
TSTAT CB
IDCB
This wire is included
in factory harness
GRA
Disconnect this wire from
TSTAT CB-X and insulate.