🔍 Key Concepts

• Hand/Auto selector switch contacts (A and B) and which one is closed in the HAND position per the small table in Figure A • How the start pushbutton, control relay CR, and the pressure switch PS are wired together in the ladder diagram in Figure B • Whether the pressure switch PS is in series with the motor-control circuit when the selector is in HAND versus AUTO

💭 Think About

• Trace the control circuit in Figure B starting at L1: go through STOP, START, CR contact, then through the HAND/AUTO selector to see what components the current must pass through to energize CR and the motor starter coil. • Compare the current path in HAND to the path in AUTO and decide: in HAND, does current still have to pass through the pressure switch PS before CR can energize, or is PS bypassed? • Ask yourself: if CR can be energized in HAND without the pressure switch, what effect does that have on when the compressor motor can run compared to AUTO, where tank pressure matters?

✅ Before You Answer

• Verify from the contact-position table which contact (A or B) is closed in HAND and which is closed in AUTO. • Confirm whether the pressure switch PS contacts are in the circuit path when the selector is in HAND; this determines if system pressure can prevent the motor from starting. • Check if there is any seal-in (holding) contact for CR that keeps the motor running after you release the START button, and whether this behavior changes between HAND and AUTO.