Pressure Switches - Carrier 50XZ024 Installation, Start-Up And Service Instructions Manual

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Fig. 29—Refrigerant Circuit
Step 9—Pressure Switches
Pressure switches are protective devices wired into control circuit
(low voltage). They shut off compressor if abnormally high or low
Quiet Defrost interval
Shift DIP switches
Fig. 28—Defrost Control
pressures are present in the refrigeration circuit. These pressure
switches are specifically designed to operate with Puron (R-410A)
systems. R-22 pressure switches must not be used as replacements
for the Puron (R-410A) system.
Step 10—Loss of Charge Switch
This switch is located on the liquid line and protects against low
suction pressures caused by such events as loss of charge, low
airflow across indoor coil, dirty filters, etc. It opens on a pressure
drop at about 20 psig. If system pressure is above this, switch
should be closed. To check switch:
NOTE: Because these switches are attached to refrigeration
system under pressure, it is not advisable to remove this device for
troubleshooting unless you are reasonably certain that a problem
exists. If switch must be removed, remove and recover all system
charge so that pressure gauges read 0 psi. Never open system
without breaking vacuum with dry nitrogen.
Step 11—High-Pressure Switch
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The high-pressure switch is located in the discharge line and
protects against excessive condenser coil pressure. It opens at 610
psig.
High pressure may be caused by a dirty outdoor coil, failed fan
motor, or outdoor air recirculation.
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1. Turn off all power to unit.
2. Disconnect leads on switch.
3. Apply ohm meter leads across switch. You should have
continuity on a good switch.
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