The main breaker tripped and I don't know why exactly

Thread Starter

rambomhtri

Joined Nov 9, 2015
557
You just mentioned two disadvantages.

Time is money for the electrician. He has no time for soldering/desoldering. What about trouble-shooting? being able to disconnect is useful, right?
When I say that, I always mean safety and performance, which is the things I care when something is not standard. Of course I understand why an electrician wouldn't solder wires, it's what I said, overkill. Not necessary to seal that good a connection in these scenarios.

I was simply worried I was being told "don't use it" because it was not safe or performance wise, and that is why I have been asking that please tell me what kind of problem can develop in a sealed soldered connection that can't in a block or wire nut. Being able to troubleshoot and disconnect is useful, of course. That's why I don't solder my PC wire to the wall outlet. I hope you realize that I solder things that are supposed to be permanent or there for a long time. This time, this lamp was not touched a single time (only bulbs replaced) for more than 40 years.
 

Thread Starter

rambomhtri

Joined Nov 9, 2015
557
When I say that, I always mean safety and performance, which is the things I care when something is not standard. Of course I understand why an electrician wouldn't solder wires, it's what I said, overkill. Not necessary to seal that good a connection in these scenarios.

I was simply worried I was being told "don't use it" because it was not safe or performance wise, and that is why I have been asking that please tell me what kind of problem can develop in a sealed soldered connection that can't in a block or wire nut. Being able to troubleshoot and disconnect is useful, of course. That's why I don't solder my PC wire to the wall outlet. I hope you realize that I solder things that are supposed to be permanent or there for a long time. This time, this lamp was not touched a single time (only bulbs replaced) for more than 40 years.
Things I have soldered in my own house: bathroom lights in the ceiling, I don't like blocks there, the circuit of the mirror is also soldered by me (there were your average blocks with screws exposed before), what else... I have repaired wall cables with little cracks or ripped rubber by doing this exact same thing. I mean, I don't solder something I know I might disassemble or change in the next 2-3 years.
 

Thread Starter

rambomhtri

Joined Nov 9, 2015
557
You said neutral has 20 V on it. So, there is a leakage current path somewhere. So, enough to trip an RCD.

Here:

View attachment 240299

is a typical schematic of a line filter. Suppose the left PE is dosconnected, but the right PE (PE') feeds other outlets.


The leakage current in the Cy's are about the same, so PE' is about 1/2 120V or 60V.

You find the filter in a switching power supply and the parallel outlets could be in a power strip. The leakage current is probably about 7 mA.

Believe me. It wrecks havoc.
I am not sure if I can affirm that. Let me explain again:

First time I saw it, several months ago, ceiling fan, I installed a new one over a pre-existing one. Just out of curiosity, I measured the neutral and hot wire in AC mode with my multi. With the ceiling switch on, I got 220V aprox, all fine. With the switch off, I was reading AC 60V, I would swear. I didn't look into it further because I was measuring out of curiosity, the previous fan was working fine, and the new one so far so good. However I commented it to the proprietary and said I was not sure if that was OK or not.

Second time, few days ago, same situation but with the light of a bedroom, and instead of 60V I was reading 20V, I can guarantee that. Switch off, of course. I checked also an outlet in that bedroom and I was reading 223 between hot and neutral, same between hot and ground, and 1.8V between neutral and ground, all AC of course.

I think I also read 100V somehow, always with the ceiling switch off, between the outlet neutral and the ceiling hot, or something like that. I am not sure because I didn't understand the readings and didn't want to look further. Lamp was working after and before, that is what I cared at that time, because if I start to look into everything I don't understand or seems fishy or wrong I would never leave from anywhere.
 

MaxHeadRoom

Joined Jul 18, 2013
28,617
Second time, few days ago, same situation but with the light of a bedroom, and instead of 60V I was reading 20V, I can guarantee that. Switch off, of course.
As I asked previously, was there any kind of load at the point of measurement?
If not, would it sustain any kind of load to it, with the voltage remaining?
Remember, a modern meter is very high impedance, so any spurious indications have to be verified, not just by the meter itself.
 

Thread Starter

rambomhtri

Joined Nov 9, 2015
557
As I asked previously, was there any kind of load at the point of measurement?
If not, would it sustain any kind of load to it, with the voltage remaining?
Remember, a modern meter is very high impedance, so any spurious indications have to be verified, not just by the meter itself.
No, the cables were just open and exposed, hot and neutral coming from the ceiling, no loads as as far as I can tell, nothing connected, just my multi in AC V mode with alligator clips to each one...

Could them hot and neutral be used in parallel in that same room or other with other devices like lamps? They could... I don't know. I just don't know how to read or comprehend the value, I always thought when you turn off a switch in a house, with regular devices that don't store energy, you would get 0 V or almost zero.
 

MaxHeadRoom

Joined Jul 18, 2013
28,617
As I already mentioned, a modern VOM can give misleading readings on 'open circuits' due to the very high impedance measuring stray currents which can be very small, you need to place a load in parallel to the meter and re-check.
 

Thread Starter

rambomhtri

Joined Nov 9, 2015
557
As I already mentioned, a modern VOM can give misleading readings on 'open circuits' due to the very high impedance measuring stray currents which can be very small, you need to place a load in parallel to the meter and re-check.
So, if you want to measure something like that, in my case a neutral and hot in the ceiling, with the switch off which you know should give you values near 0V... what kind of load should you use?
If I short them, meaning very little load, I am "cheating" because that of course is going to give me 0V. What would you suggest?

Should I short it with a simple cable to eliminate the remnant voltage and then measure it again without the short, and that would read almost 0V?
Or the stray voltage would come again?

This is problematic because if I guess those 20-60V are stray voltage, but they aren't somehow, I am shorting an energized circuit. So the only recommended thing, because of this, is to use the device someone shared here to read stray voltage, which is basically, AFAIK, a 3000 ohm load. I am noticing a lot of people and pages know how weird and confusing stray voltage is, because if you are not expecting it or didn't know about it, it makes you question your knowledge, since you are expecting 0V or so, nowhere near 50V or more.
 
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Ian0

Joined Aug 7, 2020
9,667
If the RCD tripped when you touched the neutral with an earthed soldering iron, that is exactly what I would expect to happen. Earth and neutral will be commoned at the supply side of the RCD. If you connect them together at the consumer side, it will allow some neutral current to bypass the RCD. As soon as the RCD detects the current out of balance it will trip. It only takes takes 30mA. If there was more than 30mA being used at the time it would be easy for 30mA to bypass the RCD and trip it.

As for soldering - Don‘t. The solder alloys with the copper, and at a point just where the visible joint ends, forms a very brittle alloy and the wire will tend to break at that point unless it is mechanically supported.

and definitely don’t tin wires before putting them into screw terminal blocks. The solder cold-flows under the pressure of the screw and the wire falls out.

(I did a year of metallurgy at university - a term of turbine blades, a term of steel and a term of solder!)

The only thing worse are the type of quick fit spring terminals that don’t have a button to release the wire. You have to cut them off and then the wire is too short.
 

Thread Starter

rambomhtri

Joined Nov 9, 2015
557
What do you mean it will tend to break?
I have yet to see one of my (or any other person) soldered joints break... I am not soldering cables that are supporting the Titanic, I am not soldering cables that are inside an unbalanced motor rotating at 5000 rpm making huge vibrations, I am not soldering cables to start flexing them up and down...

Besides all of this, yes, it is mechanically supported by the glued shrink tube, which goes about 1/2 an inch further in the cable. I like to use 2 different shrink tube sizes, one that is tight and protects the soldering area and a little bit of cable, and I put another tube slightly bigger to cover the whole thing plus a little bit more of cable. Both tubes with glue in the inside wall. So, my final result is wires mechanically joined, flux, solder them, clean, first shrink tube, and then second shrink tube. Most beautiful, secure and performing way I can think of to join 2 wires. There are exceptions, like high temperature environments, where of course soldering is not appropriate, but in normal temperature environments, blocks and nuts are simply worse from a technical perspective. I use blocks in modular situations where I know the joint needs to be unattached frequently for whatever reason.

I might have done it 3 or 4 times, tinning the wire before putting it inside a screw terminal block, because what I normally do if I am using blocks is bend the wire enough so it fills almost all the hole, and when I screw in the screw, the cable gets really stuck and nicely pressed. I would only tin it if I am already soldering something, which I am normally not if using blocks.
However, if the cable is tinned, when I press down with the screw I am going to deform it and make a hole in the apparently solid tinned cable. Even if there is micro-flow in the surface (I have yet to comprehend this), for it in order to get out of the terminal hole, there is still a chunk of cable trapped. How is that going to "slide" down the bolt?

1622722959542.png
Besides, again, these connections are not supposed to be supporting any kind of permanent forces, you are supposed to install these with no tension, nicely "loose" without any external forces. I have seen, hands down, way more important issues with blocks, such as excessive force cutting the wire, exposed wire before the hole, the cable barely filling anything inside the hole (too much hole for such tiny cable) and the screw all the way in doing a very weak force to press the cable, lose cables...
These are real problems that happen everyday with the standards, yet I have to read "well, due to micro vibrations and thermal movements the soldered cable could break". Really...
 
Last edited:

Ian0

Joined Aug 7, 2020
9,667
I might have done it 3 or 4 times, tinning the wire before putting it inside a screw terminal block, because what I normally do if I am using blocks is bend the wire enough so it fills almost all the hole, and when I screw in the screw, the cable gets really stuck and nicely pressed. I would only tin it if I am already soldering something, which I am normally not if using blocks.
However, if the cable is tinned, when I press down with the screw I am going to deform it and make a hole in the apparently solid tinned cable. Even if there is micro-flow in the surface (I have yet to comprehend this), for it in order to get out of the terminal hole, there is still a chunk of cable trapped. How is that going to "slide" down the bolt?
If you did that inside an electrical product for sale within Britain or the EU it would fail safety testing.
From BS EN60335 ( a while ago, before RoHS)
23.9 Stranded conductors shall not be consolidated by lead-tin soldering where they are subjected to contact pressure, unless the clamping means is constructed so that there is no risk of bad contact due to cold flow of the solder.
 

MaxHeadRoom

Joined Jul 18, 2013
28,617
So, if you want to measure something like that, in my case a neutral and hot in the ceiling, with the switch off which you know should give you values near 0V... what kind of load should you use?
For mains circuits a 60w lamp should suffice.
This would normally shunt any stray high-impedance sources that may cause a erroneous reading on the meter.
Of course, if the voltage remains and the lamp glows, you have a problem! ;)
 

Lo_volt

Joined Apr 3, 2014
316
Of course, if the voltage remains and the lamp glows, you have a problem!
MaxHeadRoom has a good suggestion. Use the incandescent lamp to "short" the neutral to earth ground. I know it's not a true short but it will help to diagnose the issue. If the lamp lights up then your neutral is likely shorted to hot somewhere else in the building and your problem is bigger than you think.

The other possibility is that the neutral is picking up potential inductively or capacitatively along the run from the entry into the building to the lamp where you were working. Putting the lamp across the neutral to earth ground should reduce this nearly to zero because the lamp has very low impedance. When you measure from neutral to earth with the lamp connecting the two, you should read zero or no more than a few millivolts.

This will also make sense regarding the hot wire. The reason that the hot wire does not trip the RCD (I don't see where you've confirmed that it's an RCD but I'm assuming so anyway, please correct me if I'm wrong) is that you've opened the switch in the room where you are working. Doing so reduced the length of wire available to inductively couple from hot to neutral which in turn reduced the stray voltage that you are reading.

I'm not sure of code requirements where you are, but I'm in the US. Here in the US when neutral inside a house is established, it is bonded to ground at a single point near the main breaker panel. I believe this is the case in the UK as well. You should check this connection as it may also be a contributing factor to what you are seeing.
 

Ian0

Joined Aug 7, 2020
9,667
For mains circuits a 60w lamp should suffice.
This would normally shunt any stray high-impedance sources that may cause a erroneous reading on the meter.
Of course, if the voltage remains and the lamp glows, you have a problem! ;)
If you short neutral to earth, you will almost certainly trip the RCD/GFI, because some neutral current flowing in the house wiring will find its way to the incoming combined-neutral-and-earth bypassing the neutral winding on the RCD. It will detect an unbalance and trip.
This will happen even if you have isolated the circuit that you are working on, unless the circuit has a double-pole isolator.
 

MaxHeadRoom

Joined Jul 18, 2013
28,617
It's a brand name of wire nuts.
Named after the inventor.
They are Probabally not so well known this way because Marrettes were invented in Canada, just as the Robertson Screwdriver was! :cool:
At the turn of the twentieth century, a young Scotsman named Bill P. Marr immigrated to Ontario, Canada.
After settling in the Toronto area, Marr was soon employed by the T. Eaton Company as a contractor for Ontario Hydro, where he worked as an electrician converting gas-lit homes.
He got a little tired of splashing solder on himself when making soldered wire joints called “solder and tape”.
Hence the invention.
 
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