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Table 11—Two-Speed Compressor
(Winding Resistance at 70°F ± 20°)
WINDING
3 TON
T1-T2
0.80
T1-T3
3.20
T1-T7
1.30
T1-T8
3.10
The 2-speed compressor is protected by an internal pressure relief
(IPR) which relieves discharge gas into compressor shell when
differential between suction and discharge pressures exceeds 500
psi.
The compressor is also protected by 3 PTC devices attached to
motor windings. The PTC resistance is sensed by the 2-speed
control. See Table 10 for resistance ranges.
Mechanically Interlocked Contactors
Interlocked contactor coils are 240v, high voltage. Electrical
shock can cause personal injury or death.
Do not bypass interlocks of contactors, as compressor damage
will occur.
The 2-speed products are equipped with mechanically interlocked
contactors. Each contactor has interconnecting linkage, providing
independent interlocks.
The 2-speed control provides the electrical interlock. The contac-
tors are supplied with 240-v coils, which reduce the va require-
ments of low-voltage (24-vac) control system.
Temperature Thermistors
Thermistors are electronic devices which sense temperature. As
the temperature increases, the resistance decreases. A thermistor is
used to sense outdoor ambient. Refer to Fig. 14 for resistance
values versus temperature.
4 TON
5 TON
0.70
0.60
2.20
1.80
1.00
1.00
2.20
2.00
19
THERMISTOR CURVE
90
80
70
60
50
40
30
20
10
0
0
20
40
TEMPERATURE (DEG. F)
Fig. 14—Resistance Values Versus Temperature
If outdoor ambient thermistor should fail, a malfunction signal
appears at 2-speed control. The control does not initiate second-
stage latching, and crankcase heater is turned on during all off
cycles.
Step 14—Final Checks
IMPORTANT: Before leaving job, be sure to do the following:
1. Securely fasten all panels and covers.
2. Tighten service valve stem caps to 1/12-turn past finger tight.
3. Leave User's Manual with owner. Explain system operation
and periodic maintenance requirements outlined in manual.
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.
60
80
100
120
A91431
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