Carrier 48PG03-16 Controls, Start-Up, Operation, Service And Troubleshooting Instructions page 90

PROBLEM
Heat Will Not Turn On.
Inadequate Heating. Inadequate Heating.
Heat Will Not Turn Off. Heat Will Not Turn Off.
48/50PG03,04
Fig. 19 --- Saturated Condensing Temperature Thermistor Location — 48/50PG03- -07
Table 98—Electric Heat Service Analysis
CAUSE
Active alarm.
No power to unit.
Unit is in minimum heat off-time, or minimum
cool-heat changeover time.
Thermostat or occupancy schedule setpoint not call-
ing for heating.
Heat forced off in Service Test mode.
No 24 vac at heater contactor. No 24 vac at heater contactor.
Open temperature limit switch on heater.
Dirty air filters.
Thermostat or occupancy schedule setpoint only
calling for W1.
Heat undersized for load.
Restricted airflow
Too much outdoor air.
Limit switch cycles heaters.
Bad heater elements.
Unit is in minimum heat on-time.
Thermostat or occupancy schedule setpoint still
calling for heating.
Heat forced on in Service Test mode.
Heater contactor failed.
SCT.A
MOTORMASTER
SENSOR
Check active alarms using ComfortLink™ Scrolling
Marquee.
Check power supply, fuses, wiring, and circuit breakers.
Check using ComfortLink Scrolling Marquee.
Check using ComfortLink Scrolling Marquee.
Check using ComfortLink Scrolling Marquee. Turn Service
Test mode off.
Check transformer and circuit breaker.
Check auto-reset limit switches on heater.
Check manual-reset limit switch (LS) on indoor fan
housing.
Check minimum airflow. Check limit switch when it is cool,
replace if open.
Replace air filters.
Allow time for W2 to energize.
Decrease load or increase size of heater.
Remove restriction.
Check economizer position and configuration. Adjust
minimum position.
Check rotation of blower and minimum airflow.
Power off unit and remove high voltage wires. Check
resistance of element, replace if open.
Check using ComfortLink Scrolling Marquee.
Check using ComfortLink Scrolling Marquee.
Check using ComfortLink Scrolling Marquee. Turn Service
Test mode off.
Power off unit. Check contactor and replace if closed.
MOTORMASTER
SENSOR
48/50PG05-07
90
REMEDY
SCT.A
C07016