Top Cap Switch Operation, Checkout And Status / Error Codes - Lennox XC20-036-230-01 Installation And Service Procedure

Top Cap Switch Operation, Checkout and Status / Error Codes

OPERATION:
Top Cap Thermal Sensor Switch (S173)
Some units are equipped with a compressor-mounted normally closed temperature switch that prevents compressor dam­
age 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 is a single-pole,
single-throw (SPST) bi-metallic switch.
COMPRESSOR TOP CAP SWITCH
(SPST BI-METALIC SWITCH,
NORMALLY OPENS AT 239-257ºF,
AND CLOSES AT 151-187ºF
SWITCH COVER
TOP OF COMPRESS0R
Figure 40. Top Cap Thermal Sensor Switch
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 meter display does not change, the switch is open. If the meter display goes to infinite,
the switch is closed.
Figure 41. Verifying Top Cap Thermal Sensor Switch
STATUS:
None
XC20
61