2nd Year Apprentice labs

[Tulsa Electrician]

https://forums.mikeholt.com/threads/multiwire-branch-circuits.2572640/page-2
This would be a good lab.
Set up some boxes with different loads and cross wire.
Then have them using a meter find and fix.
Looking for red flags along the way.
Set these up to start using single phase than three phase.
Maybe even two labs.
Single phase first than three phase once they understand.
Using the meter and unbalanced loads.
The above link touched on a lot of good info.
I posted an example in #35

 

[kwired]

https://forums.mikeholt.com/threads/multiwire-branch-circuits.2572640/page-2
This would be a good lab.
Set up some boxes with different loads and cross wire.
Then have them using a meter find and fix.
Looking for red flags along the way.
Set these up to start using single phase than three phase.
Maybe even two labs.
Single phase first than three phase once they understand.
Using the meter and unbalanced loads.
The above link touched on a lot of good info.
I posted an example in #35

Not saying there is no value in it, but troubleshooting miswiring isn't necessarily the same thing as troubleshooting things that have failed over time. Failure over time is not so easy to replicate in a lab situation. Failures over time can also tend to have variances that change with conditions where miswiring will often have more consistency with symptom presentation.

A failing connection might be more noticeable when it is carrying heavier load and might seem to disappear in light load conditions - how you reliably replicate that in a lab setup?

 

[Tulsa Electrician]

This from a few weeks back.
A panel was changed.
Two lighting circuits.
Lighting circuits are new led UFO type. Just tied to what ever by other contractor. Other fixture removed.
Each was one was in a different spot in the panle. Lucky on different lines.
Again new work inspected prior to panel change.
This lab would help with a couple different items. First identifying issues for MWBC. Move to a two pole breaker. Identify the fact the circuits are over loaded and advise customer. Teach to do some investigating prior to change out.
Visual insp would show MWBC which would require a little more work prior to change out. Take some meter reading. Properly identify prior to unhook for reconnect.
Identify any netural issues. Give customer a opportunity to resolve before it becomes an issue.
This panel was feed from a single phase transformer from a three phase system.
Primary 480 single phase.
Secondary 120/240 single phase.

Raceways in ceiling mixed up with other systems.

The pictures will show a two pole breaker was used for this MWBC.
The amp reading are greater than code allows for continues loads for these 20 amp lighting circuits.
The netural current is off and is being shared some where up in Ceiling raceway and other circuits.

To find this all other breakers were turned off to find which other netural had current so raceway could be traced out and corrected.
Since a light or two was tied into a j box with a recpt circuit which has a different netural. The wrong one was chosen and causing the issue.
The recptical circuit had no load yet netural current.
An optional theory with out other checking would be one light got tied line to line.

Any way some pics.

 

[Tulsa Electrician]

Not saying there is no value in it, but troubleshooting miswiring isn't necessarily the same thing as troubleshooting things that have failed over time. Failure over time is not so easy to replicate in a lab situation. Failures over time can also tend to have variances that change with conditions where miswiring will often have more consistency with symptom presentation.

A failing connection might be more noticeable when it is carrying heavier load and might seem to disappear in light load conditions - how you reliably replicate that in a lab setup?

Would I was hoping to do was to look for issues before they become a failure.
The lab would help identify such issues based on code compliant installs.
This will work in conjunction with the NEC finding issue and the related code artical.
Hopefully to prevent the issue to begin with. If they go in field and don't know than at some point there work not understanding will fail.

Based on pic. The breaker will run under 20 amps forever however not a code compliant install. Since there was a panle replacement the MWBC would be required to be adjacent with a handle tie or two pole breaker.

This will also help them in a remodel environment on older work.