Need info from an electrician

[calmloki]

Quote:

Originally Posted by OldShooter I have worked in maybe a half-dozen panels as an unlicensed (but MSEE) electrician. IMO dressing the wires that tight makes for an impressive looking panel but makes it difficult when changes are needed because all the wires are exactly to length. When I do similar things, I always make a loop in the wire just ahead of where it enters the breaker. That adds 3+ inches of wire, which can be useful if the wire needs to be moved and gives a little extra to work with if I have to add to it with another piece and a wire nut. The panel in the picture would be a nightmare, too, if one of the breakers had to be converted to a GFI. There would be a huge hunt to find and isolate the neutral that matches that hot. Twenty or thirty cut cable ties on the floor! So while I can admire the craftsmanship, IMO it is not a wise thing to do. Except in the poster-child case of aluminum wiring, UL (in the US) has done a pretty good job of making sure connectors are reliable. I'm never totally comfortable with the push-in wire option on things like duplex outlets but I have never had one fail. Re corrosion, I think UL tries to make sure that approved devices make "gas tight" connections where the physical pressure at the wire and connector metal/metal interface prevents oxygen or anything else from messing up the connection. Of course corrosion can still crawl in from the edges but that is why hostile environments have their own requirements. Fun to watch, like the cat videos, but all he proves is that it is not a good idea to push huge currents through small wires. US spec is 14 gauge for 15a breakers, 12 AWG for 20 amp. The real world is different of course because we don't have wires just hanging in free air. They will be in cables, like NM, in metal like conduit or Greenfield, etc. so will heat faster than his demo wire heated. But his video is an entertaining way to prove nothing. Thanks for posting.

I've owned and managed and cared for our units, all older. I use the screw down wire attachment points. I've replaced too many outlets with push in connections. Common failure is the tenant runs a plug in high wattage portable heater rather than the baseboards. The small surface connection point on the push in spring overloads and gets hot, which detempers the spring which worsens the connection until it all gets too hot and fails. Also see plug connection springs in the outlets fail in the same manner. Have also replaced more than a couple melted wire nuts. Don't think I've ever replaced a static wire that failed in the middle of a wire run - it is always the connection point absent physical damage to the wire.

I agree that while a thing of beauty that wiring panel pictured would be a massive PITA if anything needed changing.

[OldShooter]

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Originally Posted by calmloki I... I use the screw down wire attachment points. ...

Yup. Me too, except in occasional fits of laziness.

[NW-Bound]

Quote:

Originally Posted by OldShooter ... all he proves is that it is not a good idea to push huge currents through small wires. US spec is 14 gauge for 15a breakers, 12 AWG for 20 amp. The real world is different of course because we don't have wires just hanging in free air. They will be in cables, like NM, in metal like conduit or Greenfield, etc. so will heat faster than his demo wire heated. But his video is an entertaining way to prove nothing...

I find it interesting that the different connectors in the string all hold up far better than I expected.

If I were to put a bet, my money would be on the twisted wire nut to do the best, simply because it has the most contact surface between the wires.

And I would bet that the push-in Wago connector would be the 1st to go, but it hang in there.

Of course, in real life the 15A circuit breaker would have popped long before the little wire started to smoke, but 70A through the push-on connector? I was impressed. You said the guy proved or showed nothing?

On youtube, there is another guy who did a similar thing, but viewed the wire and connectors through an IR camera to see the hot spots. All the connectors were less warm than the wire. How could that be? I found that interesting.

Quote:

Originally Posted by calmloki I've owned and managed and cared for our units, all older. I use the screw down wire attachment points. I've replaced too many outlets with push in connections. Common failure is the tenant runs a plug in high wattage portable heater rather than the baseboards. The small surface connection point on the push in spring overloads and gets hot, which detempers the spring which worsens the connection until it all gets too hot and fails. Also see plug connection springs in the outlets fail in the same manner. Have also replaced more than a couple melted wire nuts. Don't think I've ever replaced a static wire that failed in the middle of a wire run - it is always the connection point absent physical damage to the wire...

Yes, the connection points would be the place to fail. That's why Mil-Spec connectors used in aerospace are deep gold plated, sealed from moisture by design, and very expensive.

[ERD50]

Quote:

Originally Posted by OldShooter I have worked in maybe a half-dozen panels as an unlicensed (but MSEE) electrician. IMO dressing the wires that tight makes for an impressive looking panel but makes it difficult when changes are needed because all the wires are exactly to length. When I do similar things, I always make a loop in the wire just ahead of where it enters the breaker. That adds 3+ inches of wire, which can be useful if the wire needs to be moved and gives a little extra to work with if I have to add to it with another piece and a wire nut. ...

Agreed - a loop makes it a lot easier to change things, and even provides a bit of slack for thermal expansion, movement, etc. That can still be done neatly, but not as neat as that picture, the loops would overlap.

Quote:

Originally Posted by NW-Bound I find it interesting that the different connectors in the string all hold up far better than I expected. Of course, in real life the 15A circuit breaker would have popped long before the little wire started to smoke, but 70A through the push-on connector? ...

But a connector can see a very high current with a direct short, it takes some time for the breaker to pop. I'd have to look it up, but I suppose a couple hundred amps for a few tens of milliseconds?

OK, found this on a quick search, didn't answer everything, but:

Circuit Breakers - UL Standards

Quote:

200% of rating - trip in 2 min. max. (<30A)

So though he tested at 70 A, we might see a breaker @ ~ 30 A not trip for ~ 2 minutes. That's a long time for an over current condition.


And of course it was beyond the scope of what a you-tuber can do, but the real test would be thousands of connectors installed by hundreds of different people under different conditions. Which one maintains the best characteristics under all that variation - not as consistent as a laboratory environment. From that criteria, I would think the WAGO conn (never saw those before) would be good (does the spring contact hold up over time/stress?), or the crimp (assuming the tool makes it hard to not get a full crimp). I like the crimp, I see those on the manufactured side of 120 V wiring a lot, lamps, inside a unit from line cord to the transformer, etc - simple, lots of contact area, simple tool.

-ERD50

[NW-Bound]

I beg to differ about the crimp connections. I have seen too many consumer products fail when a crimp connection becomes a high-ohmic contact. Usually it is an eyelet or a ring connector that is crimped onto a cord. The mechanical connection is still strong, but the electrical contact becomes bad. Could it be due to bad or poor metallic material? I don't know.

I have told this story before. When I bought my used motorhome, I installed a 2kW inverter and tested everything carefully. With the microwave oven on as a load, this inverter will draw upwards of 150A from 2 batteries wired in parallel.

I measured the voltage drop over all individual connections, and found a higher than normal drop across a crimp connection. And it was erratic. So, I wiggled it to observe that voltage drop fluctuating, and the damned AWG 2 cable came off its lug. Holy smoke!

If I did not find that bad connection and it came off while I was driving, it would have set fire to my motorhome. Numerous RVs come up in smoke each year, and I have no doubt many are of electrical nature.

[RobbieB]

Yeah, I don't trust high current crimps either, I solder the things with an 80 watt iron.

[NW-Bound]

Your post is like music to my ears.

Yes, I soldered all the lugs in my RV. But I needed a blow torch, not a soldering iron.

[travelover]

Quote:

Originally Posted by NW-Bound .........If I did not find that bad connection and it came off while I was driving, it would have set fire to my motorhome. Numerous RVs come up in smoke each year, and I have no doubt many are of electrical nature.

Totally off topic now but, I installed a circuit breaker right at my battery terminal in my camper, so if a dead short happens somewhere in the main wire, the damage can be mitigated.

[NW-Bound]

It's OK to be off topic as TexasProud sounded like he was done with this thread.

About my RV, yes I installed a 150A fuse at each battery.

And in going through the motorhome, I discovered that the AWG2 wire that linked the RV batteries to the engine battery was not fused at all. And it snaked under the motorhome through the chassis. Gah!

So, I installed a 150A fuse at each end to make sure that if the big wire cable got shorted to the chassis by chafing, it would not burn down the motorhome.

[Elbata]

I'm an AC contractor and when house was being built, I made mention of downstairs return air duct. It was installed but completely kinked.

Now this is me, but if I was your electrical contractor and you complained about a wire running behind #2 switch and wanted the wall opened up so the box could be rewired, I think I might find you a wee bit obsessive/compulsive. As far as switching #1 and #3, that should be no big deal.

[Texas Proud]

Quote:

Originally Posted by NW-Bound It's OK to be off topic as TexasProud sounded like he was done with this thread. About my RV, yes I installed a 150A fuse at each battery. And in going through the motorhome, I discovered that the AWG2 wire that linked the RV batteries to the engine battery was not fused at all. And it snaked under the motorhome through the chassis. Gah! So, I installed a 150A fuse at each end to make sure that if the big wire cable got shorted to the chassis by chafing, it would not burn down the motorhome.

For me, yes... I am through.... but I will still read the comments


As for a failure.... in my last house I had a slight burning smell for a few days... I could not track it down... finally it was a bit worse one day and it was a plug in my living room (very open house which is why it was all over).... the plug had melted!!! It never tripped the fuse even though it was hot enough to melt and burn part of the plug... I was lucky that a fire did not start... IIRC, the wires were screwed in....

[ERD50]

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Originally Posted by NW-Bound I beg to differ about the crimp connections. ....

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Originally Posted by RobbieB Yeah, I don't trust high current crimps either, I solder the things with an 80 watt iron.

OK, I wasn't speaking from any experience, it just appeared to me that a crimp provides a lot of contact area and is simple, so maybe that leads to being reliable? I wonder what accounts for the failures you saw? Maybe since the crimp doesn't really have much/any 'springiness' once it is crimped? Some of those other methods keep a spring tension on the connection throughout its life.

I agree it is a good thing to actually test for voltage drop with a high current. That will validate the connection (at least at the time it is tested). I wish that you-tuber had done that.

This is pretty easy to do at home - plug a toaster and a voltmeter into a power strip. Check voltage with toaster on/off. The voltage should not sag much (3% is NEC spec for full load, IIRC?). If you can estimate how long the run back to the box is, you can do the IR math for a better estimate.

I did that after adding a dryer socket, I really wanted to know those connections were good.

-ERD50

[ERD50]

Quote:

Originally Posted by Texas Proud ... As for a failure.... in my last house I had a slight burning smell for a few days... I could not track it down... finally it was a bit worse one day and it was a plug in my living room (very open house which is why it was all over).... the plug had melted!!! It never tripped the fuse even though it was hot enough to melt and burn part of the plug... I was lucky that a fire did not start... IIRC, the wires were screwed in....

Yes, fuses/circuit-breakers add a lot of safety, but if you have a not-full-short, it may not be enough to trip the breaker, but still can generate plenty of heat.

Just like a toaster produces plenty of heat to start a fire with something in close contact, but doesn't pop the breaker. Or a 40 watt soldering iron, drawing only ~ 1/3rd amp.

-ERD50

[Music Lover]

Quote:

Originally Posted by Texas Proud As for a failure.... in my last house I had a slight burning smell for a few days... I could not track it down... finally it was a bit worse one day and it was a plug in my living room (very open house which is why it was all over).... the plug had melted!!! It never tripped the fuse even though it was hot enough to melt and burn part of the plug... I was lucky that a fire did not start... IIRC, the wires were screwed in....

I've replaced most of the plugs in my house and have often wondered how reliable the $0.99 - $1.49 plugs really are (I'm not saying that's what was in your house)...they seem to be very cheaply made and, although they must be to code or they couldn't be sold here, I would never use them. I buy the higher quality ones that are still cheap at $3 and always connect them using the screws instead of the push in connections to ensure maximum contact and tightness.

[NW-Bound]

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Originally Posted by ERD50 OK, I wasn't speaking from any experience, it just appeared to me that a crimp provides a lot of contact area and is simple, so maybe that leads to being reliable? I wonder what accounts for the failures you saw? Maybe since the crimp doesn't really have much/any 'springiness' once it is crimped? Some of those other methods keep a spring tension on the connection throughout its life...

When I examined the failed crimp connectors, I invariably saw that the crimp was still solid but the stranded copper wire turned a darker color. The oxidization is what causes the contact to have a high resistance. Once that starts, the area gets heated more due to ohmic loss, and that avalanches until the joint completely failed.

Why some other joints such as wire nuts have better reliability? I believe that in the case of the wire nuts, the spiral wire inside the nut cuts into the soft copper wires, and the contact areas are sealed against oxidization.

The same thing happens with wires attached to a wall receptacle terminal with the screw. One needs to tighten enough to smash the copper wire to seal the contact area against air. When replacing receptacles, I often see that the copper wires have oxidized, but the areas under the screws are still bright copper. The bad and burned socket that TexasProud experienced might be due to a screw not properly tightened.

Anyway, the guy who did the video tested the string of connectors when it was still new. One has to "age" the connections for a few years to see the difference between them.

Still, I am impressed that the Wago connector worked so well. I did not expect it to stand up to 70A even when new. I believe this is widely used in Europe, and the Europeans are of course no dummies. So, there's something about the construction of that connector that makes it better than imagined.

And by the way, the aerospace connectors I saw were all with crimp contacts. A round circular connector can have hundreds of signal wires leading to it, and just one bad contact can cause a lot of grief. The wires are however not bare copper but multi-stranded and plated with something shiny (not tin). The contact pins crimped onto the wires are all gold plated.

PS. The cheap test cords I bought off eBay have notoriously bad crimp contacts between the wire and the alligator clips. This caused me a lot of grief until I found out what happened. So, I sat down and soldered them all.

[OldShooter]

Quote:

Originally Posted by NW-Bound ... the spiral wire inside the nut cuts into the soft copper wires, and the contact areas are sealed against oxidization. ... One needs to tighten enough to smash the copper wire to seal the contact area against air. ...

You are talking about the "gas tight" connections I mentioned.

Quote:

Originally Posted by NW-Bound Still, I am impressed that the Wago connector worked so well. I did not expect it to stand up to 70A even when new. I believe this is widely used in Europe, and the Europeans are of course no dummies. So, there's something about the construction of that connector that makes it better than imagined. ...

I think the design of those also creates gas tight connections when the screws are properly tightened.

Quote:

Originally Posted by NW-Bound ... aerospace connectors I saw were all with crimp contacts. ... The contact pins crimped onto the wires are all gold plated.

When asked about the reliability of a satellite electronics package, the reliability guys only want to know about the number and type of connections. Wire bonds between silicon chips and their packages, soldered plated-through holes between the package pins and the circuit board, flip-chip solder bonds, pins and sockets at the edges of the cards, ... and so on. They have failure rate numbers for every type of connection. After the electronic circuits themselves are tested and burned in and after the shake-rattle-roll testing, in the end it is the connections that dominate reliability.

[Texas Proud]

Quote:

Originally Posted by Music Lover I've replaced most of the plugs in my house and have often wondered how reliable the $0.99 - $1.49 plugs really are (I'm not saying that's what was in your house)...they seem to be very cheaply made and, although they must be to code or they couldn't be sold here, I would never use them. I buy the higher quality ones that are still cheap at $3 and always connect them using the screws instead of the push in connections to ensure maximum contact and tightness.

It was an original plug by the builder, so I am sure it was the cheapest available...

[misanman]

Had to diagnose and fix an "open neutral" a couple of weeks ago. Had a really difficult time finding it. Turned out it was a "back stab" connection failure on an outlet that was "hidden" behind a piece of furniture. At some point it had gotten hot enough to burn/melt the insulation on the neutral wire. I ended up replacing all 10 outlets on the circuit using the screw terminals.

I'm glad the offending outlet was only "hidden" behind some furniture. If it had been drywalled over or otherwise concealed it would have been nearly impossible.

[NW-Bound]

Quote:

Originally Posted by calmloki ... Don't think I've ever replaced a static wire that failed in the middle of a wire run - it is always the connection point absent physical damage to the wire...

I agree with you that it is hard to see a wire failing in the middle instead of at a connection point.

But then, I just saw the utility company having several trucks working on the driveway of a house in the neighborhood. They dug up a section of his driveway, and what could it be but a failed cable. I walked there to chat with the workers, and indeed that's what it was.

The big 0000 AWG power cable failed in the middle of a run. They said it's aluminum wire, and can fail over time due to stress from repeated heating and cooling cycles due to heavy current load. This neighborhood is 35-year old.

This cable carries power from the ground mounted transformer into the homes, and not the high voltage line feeding the transformer. I wonder what kind of splice they use, and then what keeps that from failing if a solid piece of cable failed before.

This is how big a 4/0 cable is. It can feed a few homes. The workers were not sure how many, but I guess I could tell by counting how many homes are between two adjacent ground transformers.

[Texas Proud]

As for failing in the middle of a wire run, I had that happen once...

We have a hot tub... wire was running to the heater or the pump, cannot remember which.... was having a problem and when I went to look the middle of the wire was melted... it was maybe a 3 ft run... I think they used too small of wire....