Print

Please login or register.
1 Hour 1 Day 1 Week 1 Month Forever
Login with username, password and session length

[Mike Sokol]

Found this on the ElectricianTalk.com newsletter. Most of these are really good points, especially about using a torque wrench and avoiding the smoke test. I do realize that from an electricians POV isolated grounds are silly and expensive, but from a sound-tech's POV they're useful. However, so many of my gigs are in crappy power locations that I just keep WW ISO-2 and ISO-8 audio transformers in the signal paths and don't worry about it too much. I do make a few bucks chasing ground-loop hum from installed systems, though...

Electrician at work

11 Points Every Electrician Should Know

1. If you are not using a torque wrench to tighten electrical connections chances are you are over tightening connections and damaging the conductors. Additionally, over tightening bolts stress the material and the bolt can fail during an electrical fault. Most electricians over tighten connections (other than overlooking a connection and leaving it loose by accident). I have seen this time and again. If you remove the conductors and the strands are damaged, you most likely have over tightened the connections.

2. If you are not using a Megger prior to energizing, after a fault, or anytime you have de-energized and are ready to re-energize, you are placing yourself, others with you, your customer, and company at risk.

3. We hear engineers, customers, and practically anyone in the electrical field concerned about the “ground.” Most of these parties worry about the ground electrode, when in reality this is (IN MY OPINION) the least of our worries. The number one grounding issue I see that can affect customer sensitive equipment is, grounds on the neutral conductor downstream from the main neutral to ground bond (NGB). These connections can be accidental or intentional. A simple megger test of the neutral to ground prior to energizing the service (with the bond lifted) can verify the integrity of the neutral.

4. A ground conductor is nothing but a 5th conductor in a 3-phase 4-wire system or the 4th conductor in a single phase system. This Equipment Ground Conductor (EGC) is a separate copper conductor and/or EMT rigid and other approved metallic wiring systems, in addition any and all building metallic components that are connected are part of the grounding system. This use of interconnected metal in a commercial facility as part of the EGC is very hard to avoid with steel framing concrete construction, copper piping, sprinkler systems, and metal duct. In a perfect world the EGC should not see current flat out; this conductor should have no voltage or current present at any point in the system. But in larger distribution systems there are small amounts of leakage current. Until they have insulation that is 100% effective, this will always occur. So if the system is installed properly there is only one connection between the neutral and ground, this is at the system bond at the main service or at a Separately Derived System (SDS). Installed and maintained properly there should be no measurable current (other than possible leakage current). If you can measure current at the neutral to ground bond connection, this should be investigated. As part of electrical preventative maintenance (EPM) we lift the neutral ground bond and with the service switches opened we megger the neutral to ground connection.

5. Isolated Grounds (in my opinion) are generally a waste of time. The use of IG branch circuits most likely started due to ground noise which is the result of grounds on the neutral downstream of the main NGB. Properly installed circuits and tested as noted above will negate the need to waste copper. But if the engineer or customer wishes for an IG circuit by all means take their money, but make it code compliant. To do this one needs to install two grounds and an IG receptacle. The EGC can be copper, EMT, Rigid, or whatever wiring method is required. The second equipment grounding conductor is an insulated grounding conductor; this is routed with the circuit conductors to the panel and from the panel to the service or SDS with the feeder conductors at this point the EGC is connected to termination connector in the SDS or service.

6. We service a large number of bolted pressure switches, these are typically in the range of 800-4000 amps, though 5000 and 6000 amp switches have been manufactured. The number one issue with these switches is the inability of electricians to read. The three major manufactures of bolted pressure switched Pringle (Eaton), BoltSwitch, and Square D (BoltLoc) are all operated differently and to operate any one of the three without reading the instructions (normally at or near the handle) can result is operational issues, that can lead to a switch locked open, closed, or partially closed. It is imperative to read the instructions closely.

7. In some areas bolted pressure switches have a bad reputation; normally the complaint is they are dangerous and they blow up. Yet in all the investigations, clean ups, repairs, or replacements we have completed, the following 4 reasons were the major causes for blow ups. 1 – Water in the gear, electricity and water do not mix. 2 – Operator error, the onsite personnel, be it building operating engineers or electricians closed the switch into a fault without investigating the fault. 3 – Misoperation of the opening closing mechanism. The 4th reason is with one brand in particular, Pringle, this name in some areas has become a generic term for a main switch, so a GE HPC may burn up, but the parties involved all call it a Pringle.

8. When a circuit breaker trips or fuse blows from 1 amp – 6000 amps the source of the trip must be located. Closing a switch or circuit breaker into a fault is just plain dangerous, yet many electricians continue to do this. A megger is a must for all service electricians in my opinion; a simple continuity tester is inadequate for this test. We recently were called to a job to replace the 4000 amp busway, after the onsite electrician made 3 tries to close the Siemens 4000 AMP circuit breaker. The circuit breaker contacts vaporized as well as 40’ of busway.

9. Busway is a wonderful product as long as you keep moisture from entering the enclosure. For installation the best method is to store busway in a dry location, if possible use a dehumidifier to keep the busway dry and cover it with plastic. This may just be in our area but most busway, during construction is stored in parking garages, cold and damp. Identify and megger each section as it is unloaded from the delivery truck, megger each section as it goes up, megger the run after each new section is added, and megger the complete run at completion and again prior to energizing. Energize the busway as soon as safely possible.

10. The FOP (Fall of Potential) test is a simple test that can be performed to verify newly installed circuit breakers or switches are free from high resistance connections. Additionally the FOP test can be utilized to isolate high resistance connections in distribution equipment. One simply uses a multimeter set on millivolt or the lowest voltage range and measure across the device in question. Measure from upper line side conductor to the lower end on the load conductor. Comparison readings are best, such as a 3-pole fused safety switch feeding a motor load, current should be the same on all three poles. By a process of elimination you can isolate the high resistance connection. Measure across the line to load, line to top of fuse, fuse clip to fuse clip. By making notes one can find the source of the heat. With practice one should be able to keep a mental record and have an idea if a connection could be bad just by the millivolt reading. Safety is a must in performing this and any electrical test on energized equipment.

11. Note for Troubleshooting

a. Some of the best test equipment ever made is our eyes; many issues can be located by paying attention, looking at everything and knowing what the issues are.
b. Never trust everything a customer tells you, listen to them and keep it in mind but do not let their perception of the issue be the driving force, especially if they are another electrician.
c. Do not work with blinders on, often I have headed down a path to wasted time, because I thought I knew the answer.
d. BE SAFE! Go home the same way you came to work, walking, seeing, and with all your fingers and toes.
e. While OSHA safety can seem a nuisance, it is important we follow all safety rules. PPE was designed to minimize injuries and deaths.
f. While much can be learned by the self taught method, know your limitations and do not put yourself in dangerous situations beyond your capabilities.
g. The Smoke Test is not an acceptable, approved method for determining if the work you just installed is operational.

Written by:
Brian J. Gaquin
Mid-Atlantic Power Specialist’s, Inc.

[Robert Piascik]

What's the Smoke Test?

[Mike Sokol]

What's the Smoke Test?

That's when you turn on the power and see where the smoke comes out. Not recommended with big power systems because it often results in vaporizing a lot of copper and sometimes causes an arc-flash explosion that can kill you. Seriously...

Avoiding the smoke test involves using things like Meg-ohmmeters on wire runs prior to applying full power. This stress insulation at above maximum voltages, but with very low currents, which allows you to identify where short circuits might happen without vaporizing anything. For testing sound gear on the bench such as tube amps, I often use a Variac to ramp up the AC voltage slowly so I can watch for any signs of component overheating before throwing full voltage/power at it.

[Stephen Swaffer]

Before reading the signature, I could tell this was from a power distribution standpoint.  And good points.

One I would add-given that temporary power is by definition set up and tore down more often-is that you should get in the habit of powering up one circuit at a time.  If you have a distro-all breakers off, then turn on the main then one at a time.  If nothing else, it certainly narrows down the problem to one circuit if something trips.  It also minimizes the loads being energized by a given breaker-I really hate turning on a heavily loaded breaker, that is just asking for trouble.

[Mike Sokol]

Before reading the signature, I could tell this was from a power distribution standpoint.  And good points.

One I would add-given that temporary power is by definition set up and tore down more often-is that you should get in the habit of powering up one circuit at a time.  If you have a distro-all breakers off, then turn on the main then one at a time.  If nothing else, it certainly narrows down the problem to one circuit if something trips.  It also minimizes the loads being energized by a given breaker-I really hate turning on a heavily loaded breaker, that is just asking for trouble.

And make sure you don't plug in any distro connectors with the loads on either. That will cause a lot of sparks and pitting of the contacts, eventually destroying your expensive plugs and receptacles.

[Frank DeWitt]

All electronic gear comes with smoke built in.  If it is let out the stuff won't work anymore.

Outlets come with reverse hot and neutral,  Boot leg neutral. 240 when you expected 120, and some are connected to dimmers.  I have reached the point where I won't plug anything in fancier then a lamp without testing it first.

[Cailen Waddell]

Under number 5, it may be obvious but the seperate grounding conductor should be isolated from the ECG until you get back to the NGB or SDS. This often means an isolated ground bus in panels on the way back to the NGB or SDS


Sent from my iPhone using Tapatalk

[Steve M Smith]

What's the Smoke Test?

You will know when you fail it.  Then you will need something like this:

 
Steve

[Mike Sokol]

You will know when you fail it.  Then you will need something like this:

 
Steve

My brothers and I used to race around in Triumphs back in the 70's (Spitfire, TR4A, GT) so there was a lot of smoke let out during those years. And these cars would perform the smoke test for us randomly. No need to initiate it yourself. Apparently a built-in Lucas feature.   

[Stephen Swaffer]

I had heard that replacement smoke was available, what I have been unable to find is a youtube video showing the correct method for re installing it.

Since Steve has a source, I assume he has successfully done this task a time or two.  I wonder if he would be so kind as to put together a short clip showing the correct method? 

[ProSoundWeb Community]