75
XC20
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).
Emergency 24VAC
Communicating Air
Handler or
Furnance
24VAC Thermostat
Thermostat,
RSBus
Communicating Air
Handler or
Furnance
NOTE 1 and 2
(Non−Communicating Mode)
C
Y
R
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.
NOTE 3
iComfort Wi-Fi or iComfort S30
iComfort
®
Wi-Fi
or iComfort
®
S30
THERMOSTAT
Communicating Air Handler and XC20
XC20 UNIT
XC20 UNIT
Figure 53. Emergency 24VAC System Operation
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.
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.
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