Carrier WEATHERMAKERTM TWO-SPEED 38TDB - Manual (Page 13)

Compressor Control Contactors
Low and high capacity contactor coils are 24 volts. The electronic
control board controls the operation of the low speed (C-L) and the
high speed (C-H) contactors.
TEMPERATURE THERMISTORS
Thermistors are electronic devices which sense temperature. As
the temperature increases, the resistance decreases. Thermistors
are used to sense outdoor ambient and coil temperature. Refer to
Fig. 13 for resistance values versus temperature.
If the outdoor ambient or coil thermistor should fail, a fault code
appears at two-speed control.
IMPORTANT: Outdoor Air Thermistor Placement
Mount outdoor air thermistor underneath unit base pan lip on
control box side of the unit as shown in Fig. 14. Attach to base pan
with adhesive tape. A small piece of TXV bulb insulation tape may
be used.
IMPORTANT: If outdoor air thermistor is not properly placed
underneath base pan, unit may see nuisance thermistor out of
frame faults.
Step 13—Final Checks
IMPORTANT: Before leaving job, be sure to do the following:
1. Ensure that all wiring and tubing is secure in unit before
adding panels and covers. Securely fasten all panels and
covers.
2. Tighten service valve stem caps to 1/12-turn past finger tight.
3. Leave Owner’s Manual with owner. Explain system operation
and periodic maintenance requirements outlined in manual.
4. Fill out Dealer Installation Checklist and place in customer
file.
CARE AND MAINTENANCE
For continuing high performance and to minimize possible equip-
ment failure, periodic maintenance must be performed on this
equipment. Frequency of maintenance may vary depending upon
geographic areas, such as coastal applications.
Table 6—Two-Speed Compressor
(Winding Resistance at 70°F ± 20°)
WINDING 024 036–037 048 060
Start (S-C) 2.280 1.850 1.459 0.740
Run (R-C) 0.770 0.745 0.552 0.356
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