6 ms·

>There is a good chance that if you installed GFCI in some old house it would just... trip due to shitty wiring. No, that's not true! A GFCI measures the curr

>There is a good chance that if you installed GFCI in some old house it would just... trip due to shitty wiring. No, that's not true! A GFCI measures the current going in and the current going out and if they are not equal it trips.

londons_explore 4y ago
Some old houses have exposed wiring in damp places, so there really is electricity leaking all the time. Theres probably some wire with paper insulation touching a plant root under the house, slowly steaming away. OP is correct that in this case a GFCI would trip all the time. But on the other hand, GFCI leaks are fairly easy to track down and fix, especially with the right equipment.
- cduzz 4y ago
  Doesn't that count as a feature not a bug? If I install an GFCI/AFCI on a branch and it starts tripping and I look and find that there's some iffy wiring, that seems like a problem averted. If I install these on a branch, decide that because it's not a problem (because the old breaker never tripped) I'm just ignoring the problem. People ignore problems all the time and aren't always caught out, but sometimes "rely on good luck" runs into bad luck and bad things happen.
  - ontarionick 4y ago
    The Swiss cheese model and the normalization of deviance!
  - champtar 4y ago
    100% agree, if it trip something need to be fixed, that's as simple as that.
- idiotsecant 4y ago
  Old wiring with exposed conductors (!?!?!?) is a five-alarm fire situation (maybe even literally) and needs to be fixed, it's not a casual 'lol silly house' situation.
amelius 4y ago
> No, that's not true! What if the return current goes through a different wire that was used as a quick fix for some wiring problem someone ran into 50 years ago?
- jacquesm 4y ago
  That is potentially quite dangerous, especially if that different wire is sitting on a different breaker.
  - pxx 4y ago
    Standard breakers only interrupt the hot side. Old wiring is full of shared neutral ghosts. It's not great but it isn't as dangerous as randomly dissipating the current throughout the house.
shawabawa3 4y ago
I had a GFCI installed in my 1930s built house the other week The circuit repeatedly tripped, so the electrician uninstalled it. To install the GFCI he would need to spend 1-2 days splitting circuits to find the leak(s) so instead of ~$40 + 1 hours labour it's potentially thousands of dollars
- jacquesm 4y ago
  That might still be worth tracing, you may have a fire risk or a risk of electrocution on your hand there. It really shouldn't happen. Those things are typically 30 or 50 mA and that's a lot of heat (12W worth) at 240V.
- atoav 4y ago
  Yep, that means somewhere there is current flowing through some pipe, some wall, something. And that is bad. 30mA is not much of a threshold, but it has been chosen because currents above that (or currents that flow longer than the 0,03s it should take maximum to trip an RCD will kill people. Not to speak of fire hazards. So, somewhere you have a thing, that could kill you, a firend, a loved one or whomever. And you decide to ignore it because money. Where I live, if something would happen this could land you in prison.
  - phpisthebest 4y ago
    [flagged]
    - atoav 4y ago
      Just FYI I am a certified electrical engineer and I do risk assessment as well, all the time. Certain things are "taking a risk" as in "there is sharp knife in the kitchen", others are just plain stupid like "one of the door knobs in this house is a knife". So the results of my risk assessment might just look a little different, because I am more familiar with the matter and the potential consequences than you might be. Best of luck to you.
  - shawabawa3 4y ago

londons_explore 4y ago

Some old houses have exposed wiring in damp places, so there really is electricity leaking all the time. Theres probably some wire with paper insulation touching a plant root under the house, slowly steaming away. OP is correct that in this case a GFCI would trip all the time. But on the other hand, GFCI leaks are fairly easy to track down and fix, especially with the right equipment.

cduzz 4y ago
Doesn't that count as a feature not a bug? If I install an GFCI/AFCI on a branch and it starts tripping and I look and find that there's some iffy wiring, that seems like a problem averted. If I install these on a branch, decide that because it's not a problem (because the old breaker never tripped) I'm just ignoring the problem. People ignore problems all the time and aren't always caught out, but sometimes "rely on good luck" runs into bad luck and bad things happen.
- ontarionick 4y ago
  The Swiss cheese model and the normalization of deviance!
- champtar 4y ago
  100% agree, if it trip something need to be fixed, that's as simple as that.
idiotsecant 4y ago
Old wiring with exposed conductors (!?!?!?) is a five-alarm fire situation (maybe even literally) and needs to be fixed, it's not a casual 'lol silly house' situation.

amelius 4y ago

> No, that's not true! What if the return current goes through a different wire that was used as a quick fix for some wiring problem someone ran into 50 years ago?

jacquesm 4y ago
That is potentially quite dangerous, especially if that different wire is sitting on a different breaker.
- pxx 4y ago
  Standard breakers only interrupt the hot side. Old wiring is full of shared neutral ghosts. It's not great but it isn't as dangerous as randomly dissipating the current throughout the house.

shawabawa3 4y ago

I had a GFCI installed in my 1930s built house the other week The circuit repeatedly tripped, so the electrician uninstalled it. To install the GFCI he would need to spend 1-2 days splitting circuits to find the leak(s) so instead of ~$40 + 1 hours labour it's potentially thousands of dollars

jacquesm 4y ago
That might still be worth tracing, you may have a fire risk or a risk of electrocution on your hand there. It really shouldn't happen. Those things are typically 30 or 50 mA and that's a lot of heat (12W worth) at 240V.
atoav 4y ago
Yep, that means somewhere there is current flowing through some pipe, some wall, something. And that is bad. 30mA is not much of a threshold, but it has been chosen because currents above that (or currents that flow longer than the 0,03s it should take maximum to trip an RCD will kill people. Not to speak of fire hazards. So, somewhere you have a thing, that could kill you, a firend, a loved one or whomever. And you decide to ignore it because money. Where I live, if something would happen this could land you in prison.
- phpisthebest 4y ago
  [flagged]
  - atoav 4y ago
    Just FYI I am a certified electrical engineer and I do risk assessment as well, all the time. Certain things are "taking a risk" as in "there is sharp knife in the kitchen", others are just plain stupid like "one of the door knobs in this house is a knife". So the results of my risk assessment might just look a little different, because I am more familiar with the matter and the potential consequences than you might be. Best of luck to you.
- shawabawa3 4y ago