System Refrigerant; Emergency 24Vac Operation - Lennox XC20-036-230-01 Installation And Service Procedure

Emergency 24VAC System Operation
The Y terminal located on the outdoor control allows the outdoor unit to be cycled ON and OFF using 24VAC inputs. The
outdoor unit will operate at 100% capacity in this configuration.
The following wiring diagrams display the wiring changes needed to switch a full communicating system to a non-communic­
ating system with the XC20 running in emergency mode (24VAC inputs to outdoor unit).

iComfort Wi-Fi or iComfort S30
Communicating Air Handler and XC20
Communicating Air
Handler or
Furnance
®
iComfort Wi-Fi

®
or iComfort S30
THERMOSTAT
RSBus

System Refrigerant

IMPORTANT !
The system must be operating at full capacity during
charging. Increase (heat) or decrease (cooling) the
thermostat setting by 5°F to create system demand.
Confirm outdoor unit running capacity on the
display on the outdoor control. Value should be
100%.
This section outlines the procedures to:
1.
Connect a gauge set for testing and charging as illustrated in fig­
ure 54.
2.
Check and adjust indoor airflow as described in figure 55.
3.
Add or remove refrigerant using the weigh-in method shown in
figure 56.
 Thermostat,
XC20 UNIT
NOTES:
1. Move one wire on both
indoor and outdoor controls
from terminals i+ to Y1 for
24VAC operation on air
conditioner and indoor unit.
2. Disconnect the i- wire from
terminal strip and tape.
3. Do not disconnect wires
form the XC20 R and C
terminals, both are required.
Figure 53. Emergency 24VAC System Operation
Communicating Air
Handler or
Furnance
24VAC Thermostat
C
R
Y
NOTE 1 and 2
4.
Verify the charge using the subcooling method described in fig­
ure 57.
IMPORTANT:
Unit must be operating at 100% input to be charged
properly.
ADDING OR REMOVING REFRIGERANT
This system uses HFC-410A refrigerant which operates at much
higher pressures than HCFC-22. The pre-installed liquid line filter
drier is approved for use with HFC-410A only. Do not replace it with
components designed for use with HCFC-22.
INDOOR AIRFLOW CHECK
Check airflow using the Delta-T (DT) process using the illustration in
figure 55.
The diagnostic screen on the thermostat or outdoor control 7-seg­
ment display shows indoor and outdoor motor CFMs or RPMs.
75
Emergency 24VAC
(Non−Communicating Mode)
XC20 UNIT
NOTE 3
XC20