Ruud RD17AZ - Page 24

24
Wiring
4.0 INSTALLATION
For indoor units using an ECM motor, the schematic below shows the additional relay to drive the system
to 2 stages of indoor airow. The low stage tap should be selected to deliver 75% of the high stage airow.
For existing indoor units that use a PSC motor, the modication requires a SPST relay, and is
installed per the schematic below: Note that the relay used must be properly rated for the voltage
and current used in the PSC motor. Line voltage will be present across the relay in PSC motor
applications. The low stage tap should be selected to deliver 75% of the high stage airow.
2 Stage 24V
Thermostat
Indoor
Control
Board
Field Installed
SPDT Relay
Low
Stage
IBM
COM
T1
T2
T3
T4
T5
(L)
GND
(N)
Y1
Y2
ST
-A1345-26-00
2 Stage 24V
Thermostat
Indoor
Control
Board
Field Installed
SPDT Relay
Low
Stage
High
Stage
Indoor PSC
Motor
Y1
Y2
ST-A1345-27-00