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

#### rambomhtri

Joined Nov 9, 2015
508
Hi, I was fixing things and I faced a situation that didn't understand as much as I would like. To simplify things, I was basically fixing the light of one bedroom. First thing I did was to turn off the switch, put on some insulated gloves, a nice pair of insulated boots (I know, kind of overkill but I like to get used to work with fine protection, just for the sake of it), disassembled the ceiling light and checked with my multimeter the AC voltage between the only 2 terminals: neutral and hot (no ground here). Now here's the first question:

With the switch on I got the expected 222V (EU). With the switch off, I got 20V. Why? Isn't that supposed to be zero?
I remember one time in one house, I was installing a ceiling fan and just for the sake of it checked the same thing. I got 223V with the switch on and I would swear I got 60V when the switch was off. I was kind of shocked, and told it to the person living in that house. Since everything worked and it was like that before, I didn't think about it much. However, I still don't understand how is that possible. Any ideas? Any situation where these values are normal and are not the consequences of something wrong?

OK, now for the second part. I repaired the light, it was a roof lamp, old, dirty, full of messed up connections and joints, sticky electrical taped joints, corrosion in cables... hell on earth. I sanitized everything, put new cables, everything went fine, and I put the lamp on the ceiling. Now it was time to connect the 2 lamp neutral and hot to the ceiling cables.

I went overkill here, I pretended to solder the cables, instead of using your average terminal block (they were joined before using electrical tape... yeah...). Then I was going to use heat shrink tubes with glue inside to properly insulate and protect the cables. In my opinion the best way to join 2 cables, but also the most complex and slowest, compared to terminal block, electrical tape and those common fast joints.

With the ceiling switch OFF, of course, and the soldering iron plugged to a grounded wall outlet, I proceeded to solder first the hot wire. Did it, no problem, sturdy fantastic joint. Then did the same with the neutral wire. However, as soon as the soldering iron touched the wires, the main breaker tripped. I was kind of shocked (well, may be not the best word to use here), saw the switch, it was turned off, and I started to feel stupid and incompetent for not knowing what was going on. I wouldn't attempt to repair or fix something that has anything to do with electricity if I don't completely understand and have knowledge of all the parts and how they work. So, a breaker tripping because of me, and not knowing what I am doing wrong, is something that gives me anxiety and sadness.

Anyways, I checked the ground of my iron and as I expected, the tip and all the visible metal parts are grounded, as it should be. Then I started to think.... OK, if the switch is off, that's like cutting the wires, so it's like having these 2 wires flying and insulated from everything. How is it possible that I am tripping a breaker working with 2 cables that are connected to nothing?

Then I immediately thought: oh, the switch is only cutting the hot wire, and the neutral in the ceiling is still connected to everything, it does not go through the switch. So, I realized that I was basically joining the ground of the wall outlet to the neutral of the ceiling. Can somebody explain to me how the breaker checks this and trips?
I know that one of the breakers checks the amps going through the hot wire at the beginning of the circuit (house), then checks the amps going at the end of the circuit (neutral wire). If their values are different, that means electricity is flowing somewhere else in the path, probably ground, and that breaks the circuit. Pretty clever. However, in this situation there should not be any flow of electricity from neutral to the ground, right?

Does this behavior have anything to do with the voltage being 20V with the switch off?

Anyways, what I ended up doing was heat the iron, then unplug it from the wall outlet and proceed. Right now everything is working fine and repaired. I do normally deactivate the whole house power with all the breakers whenever I work with these things, but since it was just a ceiling connection, I was wearing protection and it was very inconvenient at that moment to cut the power from everything, I just used the switch.

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#### Ya’akov

Joined Jan 27, 2019
6,856
First, soldering is not the best method of joining house wiring, at all. Old style UK terminal blocks aren't very good but Wago style connectors are excellent. Soldering has no advantage at all.

Second, is the breaker an RCD? If there is a problem with bonding somewhere, the neutral will not be at ground potential and an RCD will trip.

Joined Jul 18, 2013
26,291
Don't always trust the 20v to support any current, IOW modern VOM's are high impedance input and can register a voltage when it is just leakage etc.
Place some kind of load, lamp,etc on the 20v terminations, if there is not one already, and re-measure.

#### Ya’akov

Joined Jan 27, 2019
6,856
Don't always trust the 20v to support any current, IOW modern VOM's are high impedance input and can register a voltage when it is just leakage etc.
Place some kind of load, lamp,etc on the 20v terminations, if there is not one already, and re-measure.
Or buy one of these...

#### rambomhtri

Joined Nov 9, 2015
508
It was a friend's house, so I can't look it up now. I remember the electric box being really simple, it should have the basics, nothing fancy.

What do you mean soldering is not the best method?
As far as I know, soldering 2 cables is the absolute best way to connect them, since the actual touching parts of the cables that make them "one same thing" are not mechanically screw pressed "tiny" portions of metal or wire, but a solidified fluid (Sn+Pb) that is bonded much more to both wires. That will beat any mechanical joint, in terms of connection, electrical stability and performance. Not talking about force resistance or others totally unrelated variables.
That, plus the extra of being able to use shrinking tubes with glue inside to completely seal the connection (resulting in water proof, no exposed wires at all, dust proof, corrosion and dirty proof...). Blocks expose the screws, or have little holes, dirt and corrosion can "attack" the cable over the years, electrical tape gets messy and can be easily perforated or moved away...
I understand it is not convenient at all because it is too much trouble and too overkill for such basic connections, but anyways, if I can afford it I am happy to do it. How could a block beat a shrink glued tube protected soldered connection?

Wow, wow, wow, I am not aware of those things: voltage leakage? What does that mean? Do cables act sometimes as capacitors/coils that you have to "milk" before measuring?
I am not familiar with that. Unless working with caps and those things, I believed basic things such as home cables to hold no voltage at all, to be near absolute zero V whenever you switch off the mains or the switch.

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Joined Jul 18, 2013
26,291
BTW, you mention EU, where about ?

#### Ya’akov

Joined Jan 27, 2019
6,856
It was a friend's house, so I can't look it up now. I remember the electric box being really simple, it should have the basics, nothing fancy.

What do you mean soldering is not the best method?
As far as I know, soldering 2 cables is the absolute best way to connect them, since the actual touching parts of the cables that make them "one same thing" are not mechanically screw pressed "tiny" portions of metal or wire, but a solidified fluid (Sn+Pb) that is bonded much more to both wires. That will beat any mechanical join, in terms of connection, electrical stability and performance.
That, plus the extra of being able to use shrinking tubes with glue to completely seal the connection and make it water proof, with no exposed wire at all (blocks expose the screws, electrical tape gets messy and can be easily perforated or moved away).
I understand it is not convenient at all because it is too much trouble and too overkill for such basic connections, but anyways, if I can afford it I am happy to do it. How could a block beat a shrink glued tube protected soldered connection?
Because the goal of connecting house wiring is not the same as you are thinking. It's not just "overkill". Connections need to be inspectable, maintainable, and to code. Soldered connections are none of those.

It's a matter of the right method for the job. The Wago connectors are the best current (no pun intended) option.

It's not just the time consuming nature of soldering that's the problem, it's reliability and repeatability as well.

If a fault develops in your connections, the person who has to deal with it is not going to like your "thoroughness" much.

On the other hand, the Wagos, or even properly terminated terminal blocks, will not develop faults at any higher rate than your method but are far easier to diagnose and repair.

#### rambomhtri

Joined Nov 9, 2015
508
Because the goal of connecting house wiring is not the same as you are thinking. It's not just "overkill". Connections need to be inspectable, maintainable, and to code. Soldered connections are none of those.

It's a matter of the right method for the job. The Wago connectors are the best current (no pun intended) option.

It's not just the time consuming nature of soldering that's the problem, it's reliability and repeatability as well.

If a fault develops in your connections, the person who has to deal with it is not going to like your "thoroughness" much.

On the other hand, the Wagos, or even properly terminated terminal blocks, will not develop faults at any higher rate than your method but are far easier to diagnose and repair.
Sorry, I explained myself better here. These are the reasons why I would trouble so much to solder a cable instead of using blocks, whenever it is possible:
As far as I know, soldering 2 cables is the absolute best way to connect them, since the actual touching parts of the cables that make them "one same thing" are not mechanically screw pressed "tiny" portions of metal or wire, but a solidified fluid (Sn+Pb) that is bonded much more to both wires. That will beat any mechanical joint, in terms of connection, electrical stability and performance. Not talking about force resistance or others totally unrelated variables.
That, plus the extra of being able to use shrinking tubes with glue inside to completely seal the connection (resulting in water proof, no exposed wires at all, dust proof, corrosion and dirty proof...). Blocks expose the screws, or have little holes, dirt and corrosion can "attack" the cable over the years, electrical tape gets messy and can be easily perforated or moved away...
I understand it is not convenient at all because it is too much trouble and too overkill for such basic connections, but anyways, if I can afford it I am happy to do it. How could a block beat a shrink glued tube protected soldered connection?
If soldering a wire and use a glued shrinking tube is not to code because of inspection and maintainability, then a wire is not neither. I am literally making a wire. Dust proof, water proof, dirt proof, corrosion proof, not even air can enter. Correct me if I am wrong and explain it, because all I see is a better connection through metal bonding instead of mechanical pressure, and a closed and sealed connection versus one that is still open to air, dust and everything.

You can't say "well you could do it wrong". Then you could also put the wires in a block wrong, with copper hairs coming out the block holes, or you could cut the wire too much and have exposed wire before the holes, etc...

What kind of fault can develop in a soldered connection sealed with shrink glued tube that can not in a block connection?

BTW, you mention EU, where about ?
France, 230V and 50Hz.

Joined Jul 18, 2013
26,291

#### djsfantasi

Joined Apr 11, 2010
8,676
What kind of fault can develop in a soldered connection sealed with shrink glued tube that can not in a block connection?
Is your soldered, glued joint more or less flexible than the wire it is joining? Since there is a significant difference, vibration or thermal forces will cause the joint to fail at its borders.

This isn’t good.

Similar arguments have been identified and remediated and published in the electrical code.

I’m not more clever than years of electrical experience.

#### KeepItSimpleStupid

Joined Mar 4, 2014
5,088
The lamp acts like a resistor and probably a current dependent one.
An incadesent or LED.

The RCD measures the current difference using a current trasformer. The neutral and hot are wound on the transformer such that the currents cancel. The difference is amplified by an additional winding.

Your soldering iron provided a path to ground.

In the US, where 120V is common, I can explain the fault that explains 60V from hot to ground.

#### Ya’akov

Joined Jan 27, 2019
6,856
Sorry, I explained myself better here. These are the reasons why I would trouble so much to solder a cable instead of using blocks, whenever it is possible:

If soldering a wire and use a glued shrinking tube is not to code because of inspection and maintainability, then a wire is not neither. I am literally making a wire. Dust proof, water proof, dirt proof, corrosion proof, not even air can enter. Correct me if I am wrong and explain it, because all I see is a better connection through metal bonding instead of mechanical pressure, and a closed and sealed connection versus one that is still open to air, dust and everything.

You can't say "well you could do it wrong". Then you could also put the wires in a block wrong, with copper hairs coming out the block holes, or you could cut the wire too much and have exposed wire before the holes, etc...

What kind of fault can develop in a soldered connection sealed with shrink glued tube that can not in a block connection?

France, 230V and 50Hz.
I'm sorry but your response ignored what I said and repeated what you said. We aren't going to get anywhere with this. I'm going to move on.

#### rambomhtri

Joined Nov 9, 2015
508
@rambomhtri For that these make a nice option.

Yeah, I knew about those, but they are quite expensive and way more inconvenient than my setup. I use the solder I like the most, the flux I like the most, and the shrinking glue tubes I like the most. With those premade products, besides spending x15 times or even more than the "normal" way using your own flux, tubes and solder, you have no freedom to customize the size, you have to buy 5 or 6 different sizes, etc...

Is your soldered, glued joint more or less flexible than the wire it is joining? Since there is a significant difference, vibration or thermal forces will cause the joint to fail at its borders.

This isn’t good.

Similar arguments have been identified and remediated and published in the electrical code.

I’m not more clever than years of electrical experience.
I am not trying to be a smart-ass, so please don't treat me like I am trying.

I am honestly, frankly asking questions about why a block would be better that what I did. I am open to be wrong, but I am not open to obey because "the code" says so. This is science, and in science we don't have those attitudes. The code has a reason, and that is why I am asking. For what I can think about, my way (soldering) beats the blocks in every single aspect, it's is simply more complex and slower. If the code explicitly says do not use soldering because of this, and I find that a reason that is applicable to my works, then by all means I will not do it anymore.

Replying to your question, which is a fantastic question... the shrink tube area of course is harder, stiffer, less flexible than the cable, although it of course depends on the cable you are soldering.

You can explain further to show me in what situation this could be a problem. I don't understand what "vibration" or "thermal forces" really mean here, how can those have an impact in the soldered area. Vibration, there is not vibration at all in the cables along a house. And temperature, yeah, it varies from -10ºC to 40ºC being extremely extreme, although consider these are indoor cable joints. You can explain to me a situation where the block resists and the soldered joint fails.

I'm sorry but your response ignored what I said and repeated what you said. We aren't going to get anywhere with this. I'm going to move on.
I literally replied to every single one of your points, so I don't understand exactly what I ignored. A soldered shrink connection is as inspectable as the rest of the cable. The worst case scenario: cut the soldered portion and put a block, if for some weird reason the electrician wants to do it. A block is as obscure as an opaque shrink tube.
I asked just one simple question, perfectly fair question: what kind of problem can develop in a soldered connection that can not in a block?

Well, I know one, I can't use regular Sn Pb soldering connections in high temperature devices such as toasters, ovens... I indeed have used mechanical joints in these cases so the heat can't break the joint. Besides that, I can't think of anything.

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Joined Jul 18, 2013
26,291
I recall when the UK originated what in N.A. are called Marrettes, back then they were called 'Screw-its' but made of porcelain only, no metallic threaded interior.
They are banned now in UK and AFAIK the Marrette style are not available there either.

#### rambomhtri

Joined Nov 9, 2015
508
The lamp acts like a resistor and probably a current dependent one.
An incadesent or LED.

The RCD measures the current difference using a current trasformer. The neutral and hot are wound on the transformer such that the currents cancel. The difference is amplified by an additional winding.

Your soldering iron provided a path to ground.

In the US, where 120V is common, I can explain the fault that explains 60V from hot to ground.
It is not from hot to ground, it is from hot to neutral. I don't remember the exact number but I would sweat it was around 60V, that or 40V. This house had 20V, and always I am referring to hot and neutral, with the switch off, that supposedly breaks the hot wire.

What could be the reason, anyway?

I mean, if it is ground, it could be, as I have seen in some videos, that there is a problem in a community where the ground is electrified due to a faulty connection somewhere underground in the sewers.

A path to ground, from the neutral to ground?
How, can you explain further?

I recall when the UK originated what in N.A. are called Marrettes, back then they were called 'Screw-its' but made of porcelain only, no metallic threaded interior.
They are banned now in UK and AFAIK the Marrette style are not available there either.
I've seen those, didn't like them at all the first time I saw them, and still don't like them, not one bit, find them ugly and bad...
Screw a copper wire cable? Sounds like a total mess. I prefer blocks, hands down.
Nevertheless, I've seen professional electricians using them, although it's not common at all, last time was may be 10 years ago or so.

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#### rsjsouza

Joined Apr 21, 2014
368
The advantages of soldering wires are exactly what you mentioned: a solid connection between two wires that is very resilient to the elements.
However, there are disadvantages as well. The one I have experience is the excess heat applied to the wire during soldering: the insulation can slightly melt and become brittle over time.
@Yaakov also mentioned other factors such as:
- repeatability: when a technician is making a large amount of connections, the soldering will be slow and the process of joining two or more wires on an expensive Wago or on a cheap Marrette (if you are in the United States and maybe Canada) is much easier to get right with minimum training and practice. Of course, if you are doing this on a single connection and do not necessarily need to pass a certification test or prove to an inspector that you followed the regulations, the soldering method should not impose problems. However, if you ever tried to solder a number of wires followed by heat shrinking the connections on top of a ladder you will be glad those other connectors exist.
- repairability over time: a technician that needs to repair a connection can separate the wires much easier and faster when they are just joined or screwed in, most of the times without having to cut the wires. If you have a soldered connection (especially if it was done way too good), there is a chance the wires will have to be cut and you only have so much excess wire inside a box - do this a few times and you will end up with very little wire to work on.

Regarding the quality of the connection, the Marrette and the Wago can yield good connections, even if they are only mechanical. The extreme pressure applied at certain points of the wire surface can create minute solder joints that are very resilient to stress and create good electrical connections. Of course, these are mechanically less robust than a solid soldered connection, but it does not mean they are bad as well.

Anyways, these are the things I can think of at this time. Perhaps others will comment further.

#### ElectricSpidey

Joined Dec 2, 2017
2,183
What the heck is a Marrette? We just call them "wire nuts".

#### rambomhtri

Joined Nov 9, 2015
508
The advantages of soldering wires are exactly what you mentioned: a solid connection between two wires that is very resilient to the elements.
However, there are disadvantages as well. The one I have experience is the excess heat applied to the wire during soldering: the insulation can slightly melt and become brittle over time.
@Yaakov also mentioned other factors such as:
- repeatability: when a technician is making a large amount of connections, the soldering will be slow and the process of joining two or more wires on an expensive Wago or on a cheap Marrette (if you are in the United States and maybe Canada) is much easier to get right with minimum training and practice. Of course, if you are doing this on a single connection and do not necessarily need to pass a certification test or prove to an inspector that you followed the regulations, the soldering method should not impose problems. However, if you ever tried to solder a number of wires followed by heat shrinking the connections on top of a ladder you will be glad those other connectors exist.
- repairability over time: a technician that needs to repair a connection can separate the wires much easier and faster when they are just joined or screwed in, most of the times without having to cut the wires. If you have a soldered connection (especially if it was done way too good), there is a chance the wires will have to be cut and you only have so much excess wire inside a box - do this a few times and you will end up with very little wire to work on.

Regarding the quality of the connection, the Marrette and the Wago can yield good connections, even if they are only mechanical. The extreme pressure applied at certain points of the wire surface can create minute solder joints that are very resilient to stress and create good electrical connections. Of course, these are mechanically less robust than a solid soldered connection, but it does not mean they are bad as well.

Anyways, these are the things I can think of at this time. Perhaps others will comment further.
Of course, the reasons why you should use blocks instead of soldering joints must not be economical, or because it's time consuming. The reasons must be technical: safety, performance, resistance, etc...

A "code" does not talk about non technical stuff in a mandatory tone, or at all. I mean, the guidelines to pass certifications will never be "well, you must undo these soldered joints because they are too expensive and time consuming". It could be "undo these because these joints need to be removed weekly and redone, and the soldering, although better in most aspects, is inconvenient for this specific reason". A certification, I hope, because I don't give them, must only look for performance and safety. It is basically a guarantee that the job is done correctly, so it doesn't care if you used 40 min or 78 min, or if you used $5 or$1.

I totally agree, if I have to join 10 wires, I will not solder them, I will use blocks. But, if I can afford a nice connection here and there, I will do it instead of a block. To me it looks more professional, and of course it performs better and is safer than blocks and wire nuts.

Also, you can not say that the disadvantage of soldering is that if you perform it badly, then this. You are supposed to know how to solder if you want to solder, I check my connections, visually and physically, you are supposed to know that there must not be exposed wire in a block, you are supposed to screw tightly the connection and not weakly. You are supposed to do many things. You can't blame soldering bad is a problem but totally assume that everybody using block do it correctly. Indeed I really think it's the opposite.
How many people do you think is going to use blocks to connect wires?
99.95% probably
And solder them?
Well, almost no one. And which one is going to do it? Those that know how to do it
However, how many people, due to the apparent "easy to use" block joints, will use it in a bad way?
Hundreds, thousands. I've seen so many blocks with exposed wires, so many blocks with loose screws, or too tight they cut the wire... I really believe since blocks are sold as "everybody can do it" that you are going to find waaaaay more problems with blocks badly installed than with soldered.

It's a good point that the cable can be "eaten" time by time, but seriously... first, it is just 1 inch tops each time you must do something to that joint (I would do it after the connection because I know it will be in perfect condition) tell me the chances a soldered joint with glued shrink tube is the cause of a problem. Really, chances are negative I'm sure. And how many times are you going to change one lamp... 5 times? 5 inches. Besides, the correct thing to do with blocks is also, whenever you change them for whatever reason after 5-8 years, you cut the whole end and sanitize it. You also eat the cable over time.

Talking about safety, a month ago the neighbor upstairs flooded my bathroom. One of their water pipes under the floor (over my ceiling) started to leak overnight and there was water flowing down my ceiling through the LED lights holes. I don't know how something didn't short and tripped the breakers. A soldered connection would have protected the hot wire from the water, any other mechanical device, such as old blocks, new blocks, Marrettes... would have not avoided the hot wire to contact water. That's why we have breakers and ground, but still, soldering and protecting the whole thing with glued shrink tubes looks like the top joint for me, both electrically and regarding safety and performance. It's not that looks like, it is, and I have explained why.

I am interested though in some situations where soldering is not right. I know from experience one: high temp. If temperature is not high, in which case not only the soldering would suffer, but also the wire should be special and not your regular house one, blocks and marrettes are worse in pretty much all the technical stuff.

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#### KeepItSimpleStupid

Joined Mar 4, 2014
5,088
(soldering) beats the blocks in every single aspect, it's is simply more complex and slower.
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?

#### KeepItSimpleStupid

Joined Mar 4, 2014
5,088
I mean, if it is ground, it could be, as I have seen in some videos, that there is a problem in a community where the ground is electrified due to a faulty connection somewhere underground in the sewers.

A path to ground, from the neutral to ground?
How, can you explain further?

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

Here:

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.