Page 70
XP25
Top Cap Switch Operation, Checkout and Status / Error Codes
OPERATION:
Some units are equipped with a compressor-mounted normally closed temperature switch that prevents compressor damage
due to overheating caused by internal friction. The switch is located on top of the compressor casing. This switch senses the
compressor casing temperature and opens at 239-257°F to shut off compressor operation. The auto-reset switch closes
when the compressor casing temperature falls to 151-187°F, and the compressor is re-energized. This single-pole,
single-throw (SPST) bi-metallic switch.
TOP OF COMPRESS0R
SWITCH COVER
COMPRESSOR TOP CAP SWITCH
(SPST BI-METALLIC SWITCH,
NORMALLY OPENS AT 239-257ºF,
AND CLOSES AT 151-187ºF
Figure 49. Top Cap Thermal Sensor Switch Operation
CHECKOUT:
Using a multimeter set to ohms, with the terminals disconnected from the system, check the resistance between the two
terminals of the top cap switch. If the resistance reading is 0 ohms, the switch is closed.
Figure 50. Top Cap Thermal Sensor Switch Checkout (S173)
STATUS:
None
ERROR:
Table 15. Outdoor Control 7-Segment Display Alert Codes - Top Cap Switch
NOTE - System fault and lockout codes take precedence over system status codes (cooling, heating operating percentages or defrost/dehumidification).
Only the latest active fault or lockout codes are displayed (if present). If no fault or lockout codes are active, then system status codes are displayed. Alert
codes are also displayed on the iComfort Wi-Fi
®
thermostat.
Alert
Codes
Priority
Alarm Description
Possible Causes and Clearing Alarm
E 422
Moderate
Compressor top cap switch ex
ceeding thermal limit.
Check condenser fan motor, TEV, indoor unit blower motor, stuck reversing valve,
clogged refrigerant filter or undercharge. When error occurs with inverter slowdown
errors, check for system overcharge. Automatically clears when error is corrected.
E 442
Critical
The top cap switch has opened 5
times within one hour. As a result,
the outdoor unit is locked out
.
When compressor thermal protection sensor opens 5 times within 1 hour, outdoor stops
working. To clear, disconnect power to outdoor unit and restart.
