Hi,
You know this switches
https://en.wikipedia.org/wiki/Residual-current_device
In Spain, every house must have at least one protecting the entire
house. Typically 30 mA sensitivity.
Well, in some houses the thing seems to be temperamental and trigger >eventually for no apparent reason. Say once a month, twice a year...
So there are models that protect against harmonics (in Spain, they are
"class AC). Others are "immunized". Spanish Wikipedia says:
«Class AC residual current circuit breakers are the most commonly used, >although they are banned in many countries, such as Germany, due to
their ineffectiveness against harmonics and others. Semiconductors
generate leakage currents that are not detected by class AC circuit >breakers.1 It is symbolized by a rectangle showing a sine wave.»
«Class F residual current circuit breaker: they are used to protect
against alternating and pulsating leakage currents, as well as mixed >frequencies due to leakage in the electrical network. It is suitable for >earth leakage protection and to prevent untimely disconnections by >high-frequency drives; in case of tripping, it has a delayed effect. It
is also often referred to as a superimmunized residual current circuit >breaker.3 It is symbolized by a rectangle showing a sine wave overcoming
a second oscillation, plus a second rectangle with numerous sine waves.»
And there are other models that automatically reactivate after
triggering, with a motor.
Now, here goes the question.
Someone I know claims this automatic rearming is illegal in other
countries, like Germany, and that they are very dangerous. That the
devices are only sold in Spain. That spurious false triggerings do not
exist.
Is this true?
Ground Fault Circuit Breakers are not what you linked to in your first post.
I find these false triggers are more common with newer GFCB, maybe they react too fast to any transient or spike.
Peter W. wrote:freezer using a rearming GFCB and the rest a normal one.
Ground Fault Circuit Breakers are not what you linked to in your first post.
Carlos refers to the device in the main breaker panel like this one: https://en.wikipedia.org/wiki/Residual-current_device#/media/File:Residual_current_device_2pole.jpg
It is designed to trip if it detects a current leak and of course cuts both poles. But in general I consider a dangerous thing that it rearms automatically.
I know some people want them because if there is a false trip when you are away for some weeks then you have to throw away your frozen food and maybe the freezer if you can't remove the bad smell. Maybe there should be a special circuit for the fridge/
I find these false triggers are more common with newer GFCB, maybe they react too fast to any transient or spike.
If I were inside the house, I would disable the auto arming.
Of course,
if the fail condition remains active, it does not rearm. It is the same strategy as a person does: the thing triggers, we go to the panel and
try to arm it, maybe several times.
There was a period, the first year, when they happened every day at a
precise time, 6:30 AM I think it was. Investigating, the electrician
found out that the substation switched the main transformer up or down a notch at that time.
What he found then was that there was a lamp that was connected to one current limiter on (L) and to another for the (N) line. That was
corrected and the regular triggers disappeared. There remained spurious triggers, like once a year, which tend to happen when one is travelling
far (Murphy)
Carlos E.R. wrote:
If I were inside the house, I would disable the auto arming.
Sure one day you will forget to disable the rearming.
Of course,
if the fail condition remains active, it does not rearm. It is the same
strategy as a person does: the thing triggers, we go to the panel and
try to arm it, maybe several times.
The only way to know if the condition remains is to reapply power, so it should rearm and trip again. Not sure if it will be so fast tripping as it was the first time. If the leak was you on the bath this is not a good idea.
There was a period, the first year, when they happened every day at a
precise time, 6:30 AM I think it was. Investigating, the electrician
found out that the substation switched the main transformer up or down a
notch at that time.
What he found then was that there was a lamp that was connected to one
current limiter on (L) and to another for the (N) line. That was
corrected and the regular triggers disappeared. There remained spurious
triggers, like once a year, which tend to happen when one is travelling
far (Murphy)
Asymetric wiring is a good way to trigger the newer super-fast protectors. I know of some cases of false-trigger, they are hard to diagnose because it happens once a year. There are various opinions on the cause.
Same problem as if I am in the bath, somebody else in the kitchen, the
RCD triggers, the other person resets it manually and immediately. It
will not hold.
This is certainly bad wiring, but I fail to see why it would make the
RCD trigger every day at 6:30, when there was a voltage surge from the transformer station. The electrician that found the problem was baffled.
Once more, an observation from a US perspective.again, typically, are bonded together in the main panel. The main panel is also required to have a separate ground. The main service to the utility transformer is three-wire, typically. Just the hots and the neutral.
The basics: US residential systems are, typically 120/240 volt, single phase systems with two "Hots", a neutral and a ground. Hot-to-Hot is 240 volts @ 60 HZ ac. Hot-to-Neutral is 120 Volts AC. Ideally, Neutral and Ground are at the same potential, and,
Now, differential issues. One of the discovered weaknesses in US-code wiring early on was the multiple-devices issue. Say, there are eight receptacles on a single circuit, wired in parallel, of course. The last device in the chain is after multiplesplices or connections. Each one adding some tiny amount of resistance. So, there is some potential between the ground of the first device and the last. If the original electrician was sloppy, that potential can be sufficient to trip a ground-fault
Carlos E.R. wrote:
Same problem as if I am in the bath, somebody else in the kitchen, the
RCD triggers, the other person resets it manually and immediately. It
will not hold.
Bad idea. Water pipes and water heaters are earthed together with the rest of appliances,
if any has a short to ground it will be dumping the full mains voltage to the water pipes. If all is well this will trip the protector fast enough to save your life assuming you was taking a bath. Think about it, you really want to keep trying to seeif it keeps saving your life again and again?? Don't forget the protector could eventually fail as well.
Also keep in mind that when "it will not hold", it is connecting the power back for some milliseconds. It has no other way to detect a leak than to apply power and check. I would not keep trying if someone is in the bath.spikes coming from mains will be radiated more from one wire than the other resulting in an imbalance. Not to mention different stray capacitance and inductance caracteristics from the different wiring paths affecting the response to fast transients.
This is certainly bad wiring, but I fail to see why it would make the
RCD trigger every day at 6:30, when there was a voltage surge from the
transformer station. The electrician that found the problem was baffled.
My theory is that asymmetric wiring will behave like an antenna, a magnetic pulse for example from lighting, strong interference or heavy machinery nearby will induce a current in one wire different than the other. Also the opposite, all transients and
I don't understand how that small voltage drop in the cabling causes an imbalance in current. The earth in all appliances is supposed to be fully isolated from the hot/neutral isn't it?
- there may be something for the GF device to detect.I don't understand how that small voltage drop in the cabling causes an imbalance in current. The earth in all appliances is supposed to be fully isolated from the hot/neutral isn't it?A sensitive GF device will detect a difference between flow to the neutral and the ground, and perceive this as current going to ground.
The ground and neutral are bonded within the main panel, and there is a secondary ground feeding the main panel.
So, the full path of each circuit Neutral is from each device to the panel, where it is bonded to a local ground. From there to the Utility Transformer - which is also grounded in its location.
The full path of each circuit Ground is from each device to the panel, where it is bonded to the neutral and a local ground. It stops at the local ground.
In theory, the Neutral and the Ground should be at equal potential - thereby avoiding false trips - as that is what the GF device is looking for - current going to Ground (or somewhere), not Neutral. If the Ground and Neutral are not at equal potential
Peter Wieck
Melrose Park, PA
Peter W. wrote:potential - there may be something for the GF device to detect.
I don't understand how that small voltage drop in the cabling causes an imbalance in current. The earth in all appliances is supposed to be fully isolated from the hot/neutral isn't it?A sensitive GF device will detect a difference between flow to the neutral and the ground, and perceive this as current going to ground.
The ground and neutral are bonded within the main panel, and there is a secondary ground feeding the main panel.
So, the full path of each circuit Neutral is from each device to the panel, where it is bonded to a local ground. From there to the Utility Transformer - which is also grounded in its location.
The full path of each circuit Ground is from each device to the panel, where it is bonded to the neutral and a local ground. It stops at the local ground.
In theory, the Neutral and the Ground should be at equal potential - thereby avoiding false trips - as that is what the GF device is looking for - current going to Ground (or somewhere), not Neutral. If the Ground and Neutral are not at equal
..............................^^^^^^^....Peter Wieck
Melrose Park, PA
Thanks for explaining.
I seem to understand that the GF built in your wall plugs (we do not have them here) trips because the small voltage between neutral and ground.
That does not look like the right thing it should trip on. Even if the installation has few interconnects if you plug a heavy load the drop will develop anyway.parallel path and current will distribute proportionally, some current will flow through earth instead of neutral.
Here in 230/400V areas there is no voltage between neutral and ground (they could also be joined at the panel) but if you short them in a plug the GFCB trips, this is because the small voltage drop developed in the cabling. Shorting them creates a
Not voltage. GFCI's trip on a difference in _current_ between
neutral and line.
"....as that is what the GF device is looking for - *current* going to Ground (or somewhere), not Neutral. "<
On 2023-08-08 11:48, Jeroni Paul wrote:
Carlos E.R. wrote:
If I were inside the house, I would disable the auto arming.
Sure one day you will forget to disable the rearming.
Of course,
if the fail condition remains active, it does not rearm. It is the same
strategy as a person does: the thing triggers, we go to the panel and
try to arm it, maybe several times.
The only way to know if the condition remains is to reapply power, so
it should rearm and trip again. Not sure if it will be so fast
tripping as it was the first time. If the leak was you on the bath
this is not a good idea.
Nothing electric in the bath.
Same problem as if I am in the bath, somebody else in the kitchen, the
RCD triggers, the other person resets it manually and immediately. It
will not hold.
There was a period, the first year, when they happened every day at a
precise time, 6:30 AM I think it was. Investigating, the electrician
found out that the substation switched the main transformer up or down a >>> notch at that time.
What he found then was that there was a lamp that was connected to one
current limiter on (L) and to another for the (N) line. That was
corrected and the regular triggers disappeared. There remained spurious
triggers, like once a year, which tend to happen when one is travelling
far (Murphy)
Asymetric wiring is a good way to trigger the newer super-fast
protectors. I know of some cases of false-trigger, they are hard to
diagnose because it happens once a year. There are various opinions on
the cause.
That was around 1985...
 L  N
 |  |
 |  |
  RCD
 |  |
 |  |
 |  |
 |  |  protector
 |  +---/ o----------------------+---
 |  |  .                       |
 +-- | --/ o---- L              |
 |  |                           |
 |  |                           0 lamp
 |  |                           |
 |  |                           / switch
 |  |  protector               |
 |  +---/ o------ N             |
 |  |  .                       |
 +-- | --/ o----------------------+--
 |  |
This is certainly bad wiring, but I fail to see why it would make the
RCD trigger every day at 6:30, when there was a voltage surge from the transformer station. The electrician that found the problem was baffled.
On 2023-08-08 16:45, Jeroni Paul wrote:
Carlos E.R. wrote:
Same problem as if I am in the bath, somebody else in the kitchen, the
RCD triggers, the other person resets it manually and immediately. It
will not hold.
Bad idea. Water pipes and water heaters are earthed together with the
rest of appliances,
Not here, no.
if any has a short to ground it will be dumping the full mains voltage
to the water pipes. If all is well this will trip the protector fast
enough to save your life assuming you was taking a bath. Think about
it, you really want to keep trying to see if it keeps saving your life
again and again?? Don't forget the protector could eventually fail as
well.
Also keep in mind that when "it will not hold", it is connecting the
power back for some milliseconds. It has no other way to detect a leak
than to apply power and check. I would not keep trying if someone is
in the bath.
This is certainly bad wiring, but I fail to see why it would make the
RCD trigger every day at 6:30, when there was a voltage surge from the
transformer station. The electrician that found the problem was baffled.
My theory is that asymmetric wiring will behave like an antenna, a
magnetic pulse for example from lighting, strong interference or heavy
machinery nearby will induce a current in one wire different than the
other. Also the opposite, all transients and spikes coming from mains
will be radiated more from one wire than the other resulting in an
imbalance. Not to mention different stray capacitance and inductance
caracteristics from the different wiring paths affecting the response
to fast transients.
On 08/08/2023 11:30, Carlos E.R. wrote:
On 2023-08-08 11:48, Jeroni Paul wrote:
Carlos E.R. wrote:
There was a period, the first year, when they happened every day at a
precise time, 6:30 AM I think it was. Investigating, the electrician
found out that the substation switched the main transformer up or
down a
notch at that time.
What he found then was that there was a lamp that was connected to one >>>> current limiter on (L) and to another for the (N) line. That was
corrected and the regular triggers disappeared. There remained spurious >>>> triggers, like once a year, which tend to happen when one is travelling >>>> far (Murphy)
Asymetric wiring is a good way to trigger the newer super-fast
protectors. I know of some cases of false-trigger, they are hard to
diagnose because it happens once a year. There are various opinions
on the cause.
That was around 1985...
  L  N
  |  |
  |  |
   RCD
  |  |
  |  |
  |  |
  |  |  protector
  |  +---/ o----------------------+---
  |  |  .                       |
  +-- | --/ o---- L              |
  |  |                           |
  |  |                           0 lamp
  |  |                           |
  |  |                           / switch >>   |  |  protector               |
  |  +---/ o------ N             |
  |  |  .                       |
  +-- | --/ o----------------------+--
  |  |
This is certainly bad wiring, but I fail to see why it would make the
RCD trigger every day at 6:30, when there was a voltage surge from the
transformer station. The electrician that found the problem was baffled.
Because the incorrect wiring meant it was permanently near it's 30mA
limit and a little bit of extra harmonic content pushed it over the edge?
On 08/08/2023 22:42, Carlos E.R. wrote:
On 2023-08-08 16:45, Jeroni Paul wrote:
Carlos E.R. wrote:
Same problem as if I am in the bath, somebody else in the kitchen, the >>>> RCD triggers, the other person resets it manually and immediately. It
will not hold.
Bad idea. Water pipes and water heaters are earthed together with the
rest of appliances,
Not here, no.
if any has a short to ground it will be dumping the full mains
voltage to the water pipes. If all is well this will trip the
protector fast enough to save your life assuming you was taking a
bath. Think about it, you really want to keep trying to see if it
keeps saving your life again and again?? Don't forget the protector
could eventually fail as well.
Also keep in mind that when "it will not hold", it is connecting the
power back for some milliseconds. It has no other way to detect a
leak than to apply power and check. I would not keep trying if
someone is in the bath.
This is certainly bad wiring, but I fail to see why it would make the
RCD trigger every day at 6:30, when there was a voltage surge from the >>>> transformer station. The electrician that found the problem was
baffled.
My theory is that asymmetric wiring will behave like an antenna, a
magnetic pulse for example from lighting, strong interference or
heavy machinery nearby will induce a current in one wire different
than the other. Also the opposite, all transients and spikes coming
from mains will be radiated more from one wire than the other
resulting in an imbalance. Not to mention different stray capacitance
and inductance caracteristics from the different wiring paths
affecting the response to fast transients.
When a 30mA RCD is prone to false triggering it can mean you are trying
to feed to much stuff from it. Some leakage is normal for many devices.
Here we usually use several 30mA RCDs, maybe one for upstairs sockets,
one for downstairs sockets, one for lighting or something similar, but
making sure everything is still protected.
- there may be something for the GF device to detect.I don't understand how that small voltage drop in the cabling causes an imbalance in current. The earth in all appliances is supposed to be fully isolated from the hot/neutral isn't it?
A sensitive GF device will detect a difference between flow to the neutral and the ground, and perceive this as current going to ground.
The ground and neutral are bonded within the main panel, and there is a secondary ground feeding the main panel.
So, the full path of each circuit Neutral is from each device to the panel, where it is bonded to a local ground. From there to the Utility Transformer - which is also grounded in its location.
The full path of each circuit Ground is from each device to the panel, where it is bonded to the neutral and a local ground. It stops at the local ground.
In theory, the Neutral and the Ground should be at equal potential - thereby avoiding false trips - as that is what the GF device is looking for - current going to Ground (or somewhere), not Neutral. If the Ground and Neutral are not at equal potential
Peter Wieck
Melrose Park, PA
On 2023-08-11 16:46, Brian Gregory wrote:
Because the incorrect wiring meant it was permanently near it's 30mA
limit and a little bit of extra harmonic content pushed it over the edge?
That incorrect wiring, as plotted, doesn't increase the residual current
even one mA. There has to be something else.
At the time (1985), there were no electronic switched loads in the
network. Microwaves were barely just starting, no PC boom yet.
In theory, the Neutral and the Ground should be at equal potential -
thereby avoiding false trips - as that is what the GF device is looking
for - current going to Ground (or somewhere), not Neutral. If the Ground
and Neutral are not at equal potential - there may be something for the
GF device to detect.
In article <ubdr64$2duqe$1@dont-email.me>,
Jerry Peters <jerry@example.invalid> wrote:
In theory, the Neutral and the Ground should be at equal potential - >>thereby avoiding false trips - as that is what the GF device is looking
for - current going to Ground (or somewhere), not Neutral. If the Ground >>and Neutral are not at equal potential - there may be something for the
GF device to detect.
That's almost exactly backwards, in practice.
When the system is in use (that is, when the Hot line is drawing
current), the Neutral and Ground wires are at the same potential
*ONLY* at points where they are actually bonded together - that is, at
the panel or sub-panel or transformer.
At other points (for example, at the outlet) they won't be at the same potential. They can't be, because the neutral wire is carrying
current and has non-zero resistance, and thus has a significant
voltage drop between the outlet and the panel. The protective-ground
wire won't be carrying current, and thus has no voltage drop between
the outlet and the panel.
So, if a GFI considered "ground and neutral wires are not at equal
potential" to be a fault condition, it would trip every time somebody
turned on a light or appliance.
If you want to see this demonstrated, it's not difficult to do, if
you have an AC voltmeter with properly-shrouded insulated test leads.
Using one half of a standard outlet, measure the voltage between the
neutral and ground contacts. If nothing on that circuit is drawing
current, it should read 0 volts, or within noise-factor of that.
Then, plug a 15-amp space heater into the other half of that outlet,
and turn it on. You'll almost certainly see a significant voltage
develop between ground and neutral, caused by the current flowing
from the outlet back to the panel through the neutral wire. I'd
expect something on the order of a volt or so to show up on
the meter.
If you don't see a voltage drop between ground and neutral under
these conditions, it may very well mean that your outlet is
mis-wired, and has ground and neutral connected together at
the outlet... which is a definite no-no.
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