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.
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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