Emergency 24Vac System Operation; Thermostat Communication Mode - Lennox XP25-024-230-01 Installation And Service Procedure

Emergency 24VAC System Operation

The Y and O terminals located on the outdoor control allow the outdoor unit to be cycled ON and OFF using 24VAC inputs. The
outdoor unit will operate at 100% capacity in this configuration.
NOTE - Defrost operation will not have any indoor discharge air tempering due to the lack of a W1 out terminal.
The following wiring diagrams display the wiring changes needed to switch a full communicating system to a partial
communicating system with the XP25 running in emergency mode (24VAC inputs to outdoor unit).
iComfort Wi-Fi
Communicating Air Handler and XP25
iComfort Wi−Fi 
THERMOSTAT
RSBus
NOTES:
1. Move two wires on both indoor and outdoor controls from terminals i+ to Y1 and i- to O for 24VAC operation on heat pump and indoor unit.
2. Do not disconnect wires from the XP25 R and C terminals, both are required.
3. Cut R to O link on indoor control.
®
Thermostat
Communicating Air
Handler or
Furnance
XP25 UNIT
XC25
DO NOT CUT
Figure 62. Thermostat Communication Mode
(Non-Communicating Mode)
24VAC Thermostat
C
R
NOTE 1
O
Y
NOTE 3
XP25
CUT LINK
Page 84
Emergency 24VAC
Communicating Air
Handler or
Furnance
NOTE 2
XP25 UNIT
XP25