hands on testing (apprentices)

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ibew501ed

Senior Member
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danbury ct/work in white plains ny
In an effort to honor our apprentices before graduating (top 3,or 5) we want to have a contest
Any ideas?
pipe bending (saddles, sets, elbows in RMC)
Data punch down
rigging
troubleshooting circuitry
panel dress out

Any help would be greatly appreciated

Ed
 
100201-1358 EST

Under troubleshooting:

Create several types of flickering light problems. High resistance neutral from someplace between the transformer center tap and the main panel neutral buss bar. A normal condition resulting from the inrush current of a 240 V air conditioner turning on. Same from a electric hot plate (different symptoms -- most noticeable on only on one phase, or maybe only one circuit). High resistance in a hot line (possibly a loose screw). Power company wires too small.

Loose breaker contact with buss bar.

Early failure of incandescent lamps.

So call phantom voltage problem. Maybe related to a correctly or incorrectly wired three-way switch circuit.

Tracing the wiring of a circuit.

Voltage on plumbing fixtures. Shock in the shower.

A tripping breaker.

A motor starter contactor that does not seal in. Maybe paint on the holding contact.

Excessive current on the cold water pipe from the street.

.





.
 
Well since it's a contest:

-Who can bend a 90 in 1" Rigid the fastest (using hand bender).
-Who can carry a bundle of 1" Rigid to the 2nd floor the fastest
-Who can hand-thread a 1" nipple 12"long the fastest
-Who can keep the safety officer busy while all this goes on
 
Add some low voltage, code and theory to that and a prank on the end and you're good to go: a well-rounded test for the well-rounded apprentice.
 
ty said:
Well since it's a contest:

-Who can bend a 90 in 1" Rigid the fastest (using hand bender).
-Who can carry a bundle of 1" Rigid to the 2nd floor the fastest
-Who can hand-thread a 1" nipple 12"long the fastest
-Who can keep the safety officer busy while all this goes on
Click to expand...

Thats what I'm thinking
also
Could we have a few wires in a box and out of sight of the apprentice connect 2 to a 5ohm resister to simulate a load
connect 1 to a 100k ohm resister to gnd to simulate a high resist gnd
connect 2 to a light bulb connect 2 in a short etc....
would that be a valid test
 
gar said:
100201-1358 EST

Under troubleshooting:

Create several types of flickering light problems. High resistance neutral from someplace between the transformer center tap and the main panel neutral buss bar. A normal condition resulting from the inrush current of a 240 V air conditioner turning on. Same from a electric hot plate (different symptoms -- most noticeable on only on one phase, or maybe only one circuit). High resistance in a hot line (possibly a loose screw). Power company wires too small.

Loose breaker contact with buss bar.

Early failure of incandescent lamps.

So call phantom voltage problem. Maybe related to a correctly or incorrectly wired three-way switch circuit.

Tracing the wiring of a circuit.

Voltage on plumbing fixtures. Shock in the shower.

A tripping breaker.

A motor starter contactor that does not seal in. Maybe paint on the holding contact.

Excessive current on the cold water pipe from the street.

.





.
Click to expand...

Gar I like all of these BUT to adapt it to a contest fomat w/o killing anyone is the problem. Any Ideas?
 
ibew501ed said:
any thoughts?
Click to expand...
You might want to stick to using low voltage transformers as a supply, say 24 volt center-tap ones. Be sure to fuse the outputs as you will likely have faults. you would have to provide the proper test equipment to work on the lower voltages (test loads, etc).

As for stuff to do (may be some repeats):
Small series loads with a wire from intersection to simulate open neutral conditions. They would have to add loading to see the balance point move.
Coiled/twisted wires to simulate ghost voltages.
Add impedance in conductors to simulate voltage drop and neutral voltage rise above ground.
Correct the wiring on a scrambled three and four way switch combo having all the same color wires. They only have access to the ends of the wires.
Determine the size of several wires in a concealed box by feel only.
 
100209-1310 EST

I am not clear on your question.

You could put a small control transformer in a box so its terminals are not directly accessible. Maybe 500 to 1000 VA, small enough that it has moderate internal impedance relative to the loads you might use. Thus, I favor 500 VA. These are usually available as two primaries and two secondaries. Wire it so that the two secondaries form a center tapped 120-0-120 output. Most likely the inputs would be in parallel from 240. These transformers are usually wound about 2 to 1.

250 W lamps can provide substantial load and therefore secondary voltage change. The center tap can connect to your main EGC for safety. You can setup a system with loose connections, or specific resistance values for simulation of different problems. GFCIs should be part of the test, maybe some old ones without new features. You can simulate bad neutral connections, miswired circuits, bad hot connections, leakage resistance problems with the GFCI, voltage drop problems, phantom voltage on a three-way, have a buck transformer to create a low voltage on one phase of the supply transformer, get some old bad backstab receptacles to create their problems, have a a slightly bad transient voltage limiter that will trip the GFCI, have a KIll-A-Watt EZ meter for experiments, a 1/4 HP capacitor run induction motor (no load), a compensating capacitor for the motor, and may more possibilities. Pick what is appropriate for your student base. Do not try to fool them. Create real world problems to be found or observed.

Setup two 15 W bulbs to use to evaluate neutral problems. I can detect a 1.5 V change at 120 V with one of these bulbs.

.
 
Last edited:
100209-1608 EST

Another test. Several duplex outlets connected to a single circuit. Use #12. From the source 20 ft to the first outlet, 10 ft to the next, and 15 ft to another that is the end of a series string of three. Another branches from the middle of the first three for a distance of 20 ft. The outlets are in some random physical order close to one another such as to not divulge the wiring order. All the wiring is hidden. The task of the students is to map out this circuit and calculate the wire distance between each outlet.

.
 
gar said:
100209-1608 EST

Another test. Several duplex outlets connected to a single circuit. Use #12. From the source 20 ft to the first outlet, 10 ft to the next, and 15 ft to another that is the end of a series string of three. Another branches from the middle of the first three for a distance of 20 ft. The outlets are in some random physical order close to one another such as to not divulge the wiring order. All the wiring is hidden. The task of the students is to map out this circuit and calculate the wire distance between each outlet.

.
Click to expand...
I like that. Make 'em think.
 
100209-1710 EST

mivey:

Think!

That was an important object of one of my old profs, William G. Dow. He was a driving force behind the creation of the Upper Air Atmospheric Research Group which later became the Willow Run Laboratories and separately he was back of the creation of the Electronics Defense Group.

If you had a test question and you thought the question had a problem he would simply tell you go back and describe what you thought was wrong. It should also be noted that all our tests were on the honor system, and many were open book.

Also in EDG program review meetings when when someone was giving a presentation Dow would often ask questions that many would consider "stupid", but these questions were intended to make the presenter clarify their point because Dow realized that many in the audience were afraid to ask for a clarification.

A great deal of important work resulted from Willow Run, EDG, and Bendix Aerospace Research which was an offshoot of Willow Run. Early upper air studies, side looking radar, holography, countermeasures, signal detectability, system engineering, and many others.

For those unfamiliar with Willow Run it was an airport and B24 bomber plant built by Ford for WWII mass production of the B24. Covered about 6 square miles. The peak goal was one bomber per hour from the plant using four final assembly lines. Near the war end this goal was approximately achieved and about 2000 of these bombers per night bomber Germany. After the end of the war the University of Michigan purchased Willow Run for I believe $1.

.
 
gar said:
100209-1608 EST

Another test. Several duplex outlets connected to a single circuit. Use #12. From the source 20 ft to the first outlet, 10 ft to the next, and 15 ft to another that is the end of a series string of three. Another branches from the middle of the first three for a distance of 20 ft. The outlets are in some random physical order close to one another such as to not divulge the wiring order. All the wiring is hidden. The task of the students is to map out this circuit and calculate the wire distance between each outlet.

.
Click to expand...

Gar how do I calculate the wire distance between outlets?
resist /1000' ?
If I could learn it I could like this test...
 
gar said:
100209-1710 EST

mivey:

Think!

That was an important object of one of my old profs, William G. Dow. He was a driving force behind the creation of the Upper Air Atmospheric Research Group which later became the Willow Run Laboratories and separately he was back of the creation of the Electronics Defense Group.

If you had a test question and you thought the question had a problem he would simply tell you go back and describe what you thought was wrong. It should also be noted that all our tests were on the honor system, and many were open book.

Also in EDG program review meetings when when someone was giving a presentation Dow would often ask questions that many would consider "stupid", but these questions were intended to make the presenter clarify their point because Dow realized that many in the audience were afraid to ask for a clarification.

A great deal of important work resulted from Willow Run, EDG, and Bendix Aerospace Research which was an offshoot of Willow Run. Early upper air studies, side looking radar, holography, countermeasures, signal detectability, system engineering, and many others.

For those unfamiliar with Willow Run it was an airport and B24 bomber plant built by Ford for WWII mass production of the B24. Covered about 6 square miles. The peak goal was one bomber per hour from the plant using four final assembly lines. Near the war end this goal was approximately achieved and about 2000 of these bombers per night bomber Germany. After the end of the war the University of Michigan purchased Willow Run for I believe $1.

.
Click to expand...


I subscribe to this also.
I always as the dumb question
 
100210-1122 EST

Never worry about asking a question if you do not understand something.

Copper wire has a resistance based on the characteristics of copper, is different than aluminum, iron, stainless steel, etc. All these materials have a resistance that changes with temperature. Some over a limited temperature range may have a very small change with respect to temperature. For example Constantan. Manganin is even more stable. See http://www.allaboutcircuits.com/vol_1/chpt_12/6.html

If you have a circuit with no current flowing in the wires, then you can assume a 20 deg C temperature for the wire under normal conditions in a heated house. For #12 copper wire the resistance is about 1.588 ohms/1000 ft. A 1500 W heater has a resistance of about 10 ohms and on a 120 V circuit draws about 12 A.

Because of the thermal time constant of wire you can apply a 12 A load for a short time to a #12 copper wire with little change in resistance. If you leave the 12 A on for a long time you can see the copper wire resistance change. But to do this test you need to also be monitoring current as well as the voltage drop.

The resistance of a typical 1500 W heater will show a substantial resistance change from cold to hot.

Consider two duplex outlets connected by 10 ft of #12 copper. Put your meter between the hot terminal of one outlet and the hot terminal of the other outlet without removing cover plates. With no current flowing the voltage should read near 0 millivolts. Plug the 1500 W heater into the outlet furthest from the power source. Ideally you should measure the current, but we will assume 12 A. The voltage difference read should be 10*1.588*12/1000 = 0.191 V or 191 MV. Next move the 1500 W load to the outlet closest to the power source and the voltage difference should be near 0.

You should get essentially the same results on the neutral.

There is some small voltage drop in the termination of the wire to each outlet, but I eliminated the voltage drop of the heater plug to the outlet by using a connection point for the meter that did not include the heater plug.

.
 
ibew,

How about honoring them with a nice Fluke meter. Giving them a 'test' that most of the

long time Electricians could not even figure out may not be such a good idea.
 
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