17
8.4 Capacitor
A run capacitor is wired across the auxiliary and main winding of a single phase permanent split
capacitor motor such as the compressor. A single capacitor can be used for each motor or a dual
rated capacitor can be used for both.
The capacitor's primary function is to reduce the line current while greatly improving the torque
characteristics of a motor. The capacitor also reduces the line current to the motor by improving the
power factor of the load. Run capacitor hook-up line side of the capacitor is marked with a red dot
and is wired to the line side of the circuit
Capacitor test:
1. Remove capacitor from unit.
2. Check for visual damage such as bulges, cracks, or leaks
3. For dual rated, apply an ohmmeter lead to common (C) terminal and the other probe to the
compressor (HERM) terminal. A satisfactory capacitor will cause a deflection on the pointer,
and then gradually move back to infinity.
4. Reverse the leads of the probe and momentarily touch the capacitor terminals. The
deflection of the pointer should be two times that of the first check if the capacitor is good.
5. Repeat steps 3 and 4 to check fan motor capacitor.
NOTE: A shorted capacitor will indicate a low resistance and the pointer will move to the "0"
end of the scale and remain there as long as the probes are connected.
An open capacitor will show no movement of the pointer when placed across the terminals of
the capacitor
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