Junior class troubleshooting problems

Again, list the meter, settings, how leads are connected, and your reasoning for your solution.

Scenario 1:

A homeowner is renovating and upstairs room.  The room used to be a kitchen but the homeowner wants to convert it into a bedroom.  The homeowner wishes to remove a light and single pole switch that controls the light but is unsure where the circuit feed originates. This switch does turn the ceiling light on and off.   Upon arriving, you turn the switch OFF and remove the light from its ceiling box.  There is a 14/2 NM cable in the ceiling box.  You carefully remove the single pole switch and again, there is only a 14/2 NM cable in the switch box.  How could you verify the black wire at the switch is the same black wire at the light ?  Once you proved this wire IS the same, how is it possible that this light/switch works ?  What Code violation makes this circuit possible ?

Scenario 2:

A customer calls to complain about a faulty UP DOWN OFF switch that controls a commercial grade garage door opener.  There are 2 limit switches installed, one that stops the door motor at the top of the opening and one that stops the door motor when it hits the concrete fully closed.  There is no memory; the operator UP or DOWN must be held closed.  The complaint is this:  The upper limit switch stops the door when it is fully open but the door motor shuts off just seconds after the door is closed, meaning, each time the door is closed, someone needs to reset the OL relay on the magnetic motor starter.  What is the first thing you check ?  What is one possible cause of the problem ?

Junior troubleshooting problem

A customer complains that their motor keeps turning off when it is lifting a load. 

 The motor is a 480V 3 phase induction run motor which powers a lift gate for a loading dock.  When a load greater than 500 pounds is placed on a metal plate, the plate activates a pressure switch that starts the motor and moves a lift gate which lifts the load up so it can be loaded onto a truck. There is an emergency stop button and flush mounted start button near the loading dock platform. There is a limit switch that stops the motor when it reaches the loading lock.

The motor is accessible under the loading dock.  It is fed from a combination starter located in sight (per NEC) of the dock.  The combination starter contains a fusible disconnect, magnetic motor starter, control transformer, and selector switch ( hand-off-auto).  When in HAND position, the motor runs when the start button at the dock is pressed and held and the pressure switch reads more than 500 pounds, no memory.  In the AUTO position, when a load 500 pounds or greater is placed on the plate, the motor starts automatically with memory and shuts off when the load reaches the limit switch.

The combination starter is fed from a 480V 30 A 3 phase breaker in a distribution panel located 150 feet away from the loading dock. All control devices are 120 volts fed from the combination starter.

Answer the following questions indicating what test equipment you would use, the setting, and how test leads are connected.  Give reasoning for your answers. It may help to draw a ladder diagram to assist you in determining the order of troubleshooting.

1.  What is the first thing you check upon arriving at this site?

2.  Determining that step 1 was not the problem, what do you check next?

3.  Determining that step 2 was not the issue, what do you check next?

4.  Finding that step 3, was not the problem, you decide to do a test. You go to the combination starter and place the selector switch in the HAND position. You place a load greater than 500 pounds on the plate. You press and hold the start button and the lift works fine.  You switch to the AUTO position; You hear the motor start and the plate starts to rise.  About 6 inches above the floor, the plate stops and you hear the motor is off.  Where do you go and what do you check ?

5.  What is the problem?

and more Pythagorean help

another explanation:

The Pythagorean Theorem

The Pythagorean theorem, an important mathematical principle, uses right triangles. A right triangle is a triangle which has one right or 90° angle. The side opposite the 90° angle is called the hypotenuse .

The Pythagorean theorem states that for any right triangle c ² = a ² + b ² , where c is the length of the hypotenuse and a and b are the lengths of its sides (see Fig. 9-23 ) .

Fig. 9-23.

Finding the Hypotenuse

If you need to find the hypotenuse of a right triangle, use c = .

Finding the Sides of a Right Triangle

If you need to find the length of one side of a right triangle, use a = or b = .

more pythagorean theory help

some examples:

Example 1

Find the length of the hypotenuse of a right triangle if the length of its sides are 5 inches and 12 inches.

Solution 1

Example 2

A person drives 33 miles due east, then makes a left turn, and drives 56 miles north. How far is he from his starting point?

Solution 2

The right triangle is shown in Fig. 9-24.

Fig. 9-24.

Then

pythagorean theory help

here is a link that may be helpful to you.  

 http://www.mathwarehouse.com/geometry/triangles/how-to-use-the-pythagorean-theorem.php


once the link opens, scroll down and click on the play arrow for the video.

you may also might want to check out all the examples shown.

magnetic motor starter quiz

 

1.  Will this mag work properly on a three-phase motor?  Support your answer.

2.  If your answer to # 1 was no, list one way this mag could work temporarily.

3.  If your answer to # 1 was no, list one reason why it would not work.

4.  There are two red wires attached to the coil.  One goes to _____ the other to ____.

5.  What is the coil voltage of this mag? 

JUNIORS: Slips Trips and Falls quiz

on a lined piece of paper write your full name, today's date, and the words "Slips Trips and Falls quiz".  you only need to write the numbers and answers.  this will be graded as a shop homework assignment.

 Slips, Trips and Falls Quiz

Name: __________________________________________________________

1. What can improve traction on floors that are frequently wet?

a. Strap cleats onto your shoes.

b. Painting gritty coatings on the floor.

c. Using a greasy floor finish.

d. Putting up a sign.

2. If you carry loads that you can’t see over or around:

a. Make sure you have good lighting.

b. Stay off the stairs.

c. Take small steps.

d. You could trip and fall; don’t carry such loads.

3. Loose carpeting, stair treads and floor tiles:

a. Are tripping hazards.

b. Should be covered with a rubber mat.

c. Should be reported right away.

d. Both a and c.

4. What is a safe way to move materials up a ladder?

a. Hoist them up using a rope after you climb the ladder.

b. Have someone throw them up to you when you reach the top.

c. Carry them in one arm as you climb.

d. All of the above.

5. When is it safe to stand on the top step of a stepladder?

a. When you can’t get a longer ladder.

b. When you can hold on to a sturdy item above while you work

c. When the ladder is less than six feet tall.

d. Never.

Slips, Trips and Falls

6. Which of the following fall protection systems prevents falls?

a. Safety net systems

b. Guardrail systems

c. Personal fall arrest systems.

d. None of the above.

7. Ladder cages are used with:

a. Scaffolds

b. Stepladders

c. Ladders that are fixed to a building or structure

d. Portable extension ladders.

8. In a personal fall arrest system, OSHA recommends the use of:

a. Full body harnesses.

b. Body belts.

c. Safety nets.

d. None of the above.

9. What is used to support a worker on a vertical surface so he or she can work with both hands free?

a. A deceleration device.

b. A positioning device system.

c. A ladder cage.

d. A safety net system.