Inst ToolsInst ToolsInst Tools
  • Courses
  • Automation
    • PLC
    • Control System
    • Safety System
    • Communication
    • Fire & Gas System
  • Instrumentation
    • Design
    • Pressure
    • Temperature
    • Flow
    • Level
    • Vibration
    • Analyzer
    • Control Valve
    • Switch
    • Calibration
    • Erection & Commissioning
  • Interview
    • Instrumentation
    • Electrical
    • Electronics
    • Practical
  • Q&A
    • Instrumentation
    • Control System
    • Electrical
    • Electronics
    • Analog Electronics
    • Digital Electronics
    • Power Electronics
    • Microprocessor
  • Request
Search
  • Books
  • Software
  • Projects
  • Process
  • Tools
  • Basics
  • Formula
  • Power Plant
  • Root Cause Analysis
  • Electrical Basics
  • Animation
  • Standards
  • 4-20 mA Course
  • Siemens PLC Course
Reading: Air Compressor Control Circuit Problem
Share
Font ResizerAa
Inst ToolsInst Tools
Font ResizerAa
  • Courses
  • Design
  • PLC
  • Interview
  • Control System
Search
  • Courses
  • Automation
    • PLC
    • Control System
    • Safety System
    • Communication
    • Fire & Gas System
  • Instrumentation
    • Design
    • Pressure
    • Temperature
    • Flow
    • Level
    • Vibration
    • Analyzer
    • Control Valve
    • Switch
    • Calibration
    • Erection & Commissioning
  • Interview
    • Instrumentation
    • Electrical
    • Electronics
    • Practical
  • Q&A
    • Instrumentation
    • Control System
    • Electrical
    • Electronics
    • Analog Electronics
    • Digital Electronics
    • Power Electronics
    • Microprocessor
  • Request
Follow US
All rights reserved. Reproduction in whole or in part without written permission is prohibited.
Inst Tools > Blog > Practical Questions > Air Compressor Control Circuit Problem

Air Compressor Control Circuit Problem

The air compressor control circuit has a problem and unable to start even when the air pressure is zero PSI.

Last updated: October 23, 2020 11:20 am
Editorial Staff
Practical Questions
No Comments
Share
3 Min Read
SHARE

This air compressor control circuit has a problem. The air compressor refuses to start even when the air pressure is zero PSI.

Air Compressor Control Circuit

Air Compressor Control Circuit has a Problem

A technician begins diagnosing the circuit, following the steps shown (in order):

Test 1: Measured 120 VAC between points A and C, with “Hand/Off/Auto” switch in the “Auto” position.

Test 2: Measured 120 VAC between points A and D, with “Hand/Off/Auto” switch in “Auto” position.

Test 3: Measured 0 VAC between points E and C, with “Hand/Off/Auto” switch in “Auto” position.

Test 4: Jumpered points A and B, with “Hand/Off/Auto” switch in “Auto” position. The motor did not start.

Identify any useful information about the nature or location of the fault derived from the results of each test, in order of the tests performed. If the test is not useful (i.e. provides no new information), mark it as such.

Assuming there is only one fault in the circuit, identify the location and nature of the fault as precisely as you can from the test results shown above.

Answer:

Test 1: Measured 120 VAC between points A and C, with “Hand/Off/Auto” switch in the “Auto” position. Proves there is 120 VAC control power available, that the fuse is good, and that the Hand/Off/Auto switch is passing power through to point A.

Test 2: Measured 120 VAC between points A and D, with “Hand/Off/Auto” switch in “Auto” position. Proves there is an “open” fault somewhere between those points, in one of the two switches, and that we do not have any other “open” faults in the contactor coil circuit.

Test 3: Measured 0 VAC between points E and C, with “Hand/Off/Auto” switch in “Auto” position. This is an unnecessary test, as we already know there is continuity through the overload contact.

Test 4: Jumpered points A and B, with “Hand/Off/Auto” switch in “Auto” position. The motor did not start. Combined with the results of previous tests, this test proves the “open” fault must lie between points B and D: namely the PSH.

The fault is an “open” high pressure switch (PSH), or in the wires connecting the PSH to points B and D.

Share your answers with us through the below comments section.

Read Next:

  • Compressor Seal Oil System
  • PLC Compressor Logic
  • Instrument Air Compressor
  • Liquid Level Switch Control
  • PLC Water Level Control Logic

Credits: Tony R. Kuphaldt

Don't Miss Our Updates
Be the first to get exclusive content straight to your email.
We promise not to spam you. You can unsubscribe at any time.
Invalid email address
You've successfully subscribed !

Continue Reading

Distillation Tower Displacer Level Instrument Check
Baffle Nozzle Assembly Sensitive Mechanism
Heat Exchanger Differential Pressure Transmitter
Questions on Dip Tube Type Level System
Pneumatic Relay Questions
Calculate the Magnitude of Hydrostatic Pressure
Share This Article
Facebook Whatsapp Whatsapp LinkedIn Copy Link
Share
Leave a Comment

Leave a Reply Cancel reply

Your email address will not be published. Required fields are marked *

Stay Connected

128.3kFollowersLike
69.1kFollowersFollow
210kSubscribersSubscribe
38kFollowersFollow

Categories

Explore More

Identify Instrumentation Terms in Water Supply System
Something is Wrong with Strain Gauge Bridge Circuit
Calculate Hydraulic System Fluid Pressure
Programmable Logic Controller (PLC) Questions and Answers – 12
Signal Strength of Guided-wave Radar Level Instrument
Three-valve Manifold on Remote Seal DP Transmitter
Motion-Balance and Force-Balance Instruments
Simple High Level Indicator Circuit

Keep Learning

compressor emergency shutdown system

Solenoid Valves Questions & Answers – 2

steadily pour a liquid into vertical tube

Vertical Tube Liquid Level Equilibrium

PLC program pushbutton switches

PLC Permissive for Motor Control

Steam flow to the heat exchanger

Analytical Control System of Heat Exchanger Questions

Calculate the amount of voltage at Thermocouple

Calculate the Voltage across Voltmeters of Thermocouple

PLC Program for Valves

PLC Pump Permissive Interlocks

Stilling well in liquid level measurement

Stilling Well in Interface Level Measurement System

Span of Pressure Gauge

How to Decrease Span of Pressure Gauge?

Learn More

Electro Magnetic Flow Meter Animation

Magnetic Flow Meter Animation

Erratic Radar Level Gauges

Erratic Radar Level Gauges Delays a Refinery Commissioning

Temperature Coefficient of Resistance

Temperature Coefficient of Resistance (α)

Diodes Voltage Quadrupler

Diodes Voltage Quadrupler

Open Tank DP Level Measurement

Open Tank DP Level Transmitter Calculations

DP Level Measurement Problems

DP Level Measurement Problems

Left-Hand Rule for Generators

Starting of DC Motors

PLC Example on Manufacturing Line Assembly

PLC Example on Manufacturing Line Assembly

Menu

  • About
  • Privacy Policy
  • Copyright

Quick Links

  • Learn PLC
  • Helping Hand
  • Part Time Job

YouTube Subscribe

Follow US
All rights reserved. Reproduction in whole or in part without written permission is prohibited.
Welcome Back!

Sign in to your account

Username or Email Address
Password

Lost your password?