5 ms·

I don't know what's going on here, but my old Mac Pro would always trip the AFCI circuit breaker when I turned it on, even with little else on the circuit. It

by simmons 10y ago

I don't know what's going on here, but my old Mac Pro would always trip the AFCI circuit breaker when I turned it on, even with little else on the circuit. It must have been taking a big gulp of power that resembled an arc-fault. Perhaps some laptop power supplies could also have weird characteristics that trip such a breaker even without exceeding the current threshold, and be interpreted in storytelling as "blowing out the fuses."

yardie 10y ago
The GFCI is not a circuit breaker. It measures the difference between the current going in and the current going out over the hot and neutral wire. If it's faulting either the circuit is faulty (your Pc) or the GFCI is faulty. If the current isn't flowing back out through neutral it means it's going directly to ground or it's going through a human, to ground. The current threshold is 50mA
- simmons 10y ago
  This wasn't a GFCI, but an AFCI. According to Wikipedia, AFCI's "detect electrical current alternating at characteristic frequencies, usually around 100 kHz, known to be associated with wire arcing, which are sustained for more than a few milliseconds." I suppose the Mac Pro's power supply produced some of these indicators, since all was well on a non-AFCI circuit. I've heard other people having similar false positives with equipment on AFCI-protected circuits.
  - meta_AU 10y ago
    Many isolated flyback AC/DC converters run around the 100kHz mark, so probably on the right track there.
    - seanp2k2 10y ago
      My Airocide (air purifier) would trip the bathroom outlet on turn-on at a place I lived. Never figured out why, but I thought that the thing was broken when I first got it.
  - yardie 10y ago
    Oh, thanks for clarifying I thought an AFCI=GFCI=RCD=RCCB.
- ptaipale 10y ago
  Well, a GFCI (elsewhere known as RCCB, residual-current circuit breaker) is a circuit breaker in the very literal sense that it breaks the circuit when it detects a current leak. But it's not exactly a fuse: if all current goes where current is supposed to go, a ground defect circuit breaker does nothing. About the previous post: that ""a laptop so powerful that it blew the fuses"" is rubbish. Even a powerful laptop doesn't eat so much current that it would blow a fuse - unless the circuit is already nearly overloaded, in which case even the slightest power consumption may blow the fuse, and that tells nothing about the power consumption of the laptop. (Used to have a kitchen where the tumble drier had to be turned off if you wanted to use the microwave or a tea kettle.)
  - cardiffspaceman 10y ago
    In most jurisdictions you wouldn't be able to build the house in such a way that such obviously-used-at-the-same-time devices would end up on the same circuit. Source: Am about to be the client of an electrical contractor due to a remodel that has to be done to code.
    - yardie 10y ago
      You can't build a new house that way. I've lived in some very old places where the underlying electrical system is absolutely terrifying, i.e. AC wires wrapped in waxed paper. I also believe the poster is in the UK. Older homes use a ring system where the breaker is at each outlet and there is one main breaker for the entire house, there is no breaker panel in the American/European sense.
      - ptaipale 10y ago
        Yes, I had those waxed paper insulated wires. You really don't want to touch them. This was in Finland, and the house was built by a refugee family at a time when building materials were difficult to get. It was in fact surprisingly good, but still the original electric works plus 50 years of DYI maintenance produced some interesting results, like disintegrating insulations and ground wires not connected to anything. The woodworks of the house were very good but fixing the electricity, heating and plumbing was hopeless.

by simmons 10y ago

yardie 10y ago

The GFCI is not a circuit breaker. It measures the difference between the current going in and the current going out over the hot and neutral wire. If it's faulting either the circuit is faulty (your Pc) or the GFCI is faulty. If the current isn't flowing back out through neutral it means it's going directly to ground or it's going through a human, to ground. The current threshold is 50mA

simmons 10y ago
This wasn't a GFCI, but an AFCI. According to Wikipedia, AFCI's "detect electrical current alternating at characteristic frequencies, usually around 100 kHz, known to be associated with wire arcing, which are sustained for more than a few milliseconds." I suppose the Mac Pro's power supply produced some of these indicators, since all was well on a non-AFCI circuit. I've heard other people having similar false positives with equipment on AFCI-protected circuits.
- meta_AU 10y ago
  Many isolated flyback AC/DC converters run around the 100kHz mark, so probably on the right track there.
  - seanp2k2 10y ago
    My Airocide (air purifier) would trip the bathroom outlet on turn-on at a place I lived. Never figured out why, but I thought that the thing was broken when I first got it.
- yardie 10y ago
  Oh, thanks for clarifying I thought an AFCI=GFCI=RCD=RCCB.
ptaipale 10y ago
Well, a GFCI (elsewhere known as RCCB, residual-current circuit breaker) is a circuit breaker in the very literal sense that it breaks the circuit when it detects a current leak. But it's not exactly a fuse: if all current goes where current is supposed to go, a ground defect circuit breaker does nothing. About the previous post: that ""a laptop so powerful that it blew the fuses"" is rubbish. Even a powerful laptop doesn't eat so much current that it would blow a fuse - unless the circuit is already nearly overloaded, in which case even the slightest power consumption may blow the fuse, and that tells nothing about the power consumption of the laptop. (Used to have a kitchen where the tumble drier had to be turned off if you wanted to use the microwave or a tea kettle.)
- cardiffspaceman 10y ago
  In most jurisdictions you wouldn't be able to build the house in such a way that such obviously-used-at-the-same-time devices would end up on the same circuit. Source: Am about to be the client of an electrical contractor due to a remodel that has to be done to code.
  - yardie 10y ago
    You can't build a new house that way. I've lived in some very old places where the underlying electrical system is absolutely terrifying, i.e. AC wires wrapped in waxed paper. I also believe the poster is in the UK. Older homes use a ring system where the breaker is at each outlet and there is one main breaker for the entire house, there is no breaker panel in the American/European sense.
    - ptaipale 10y ago
      Yes, I had those waxed paper insulated wires. You really don't want to touch them. This was in Finland, and the house was built by a refugee family at a time when building materials were difficult to get. It was in fact surprisingly good, but still the original electric works plus 50 years of DYI maintenance produced some interesting results, like disintegrating insulations and ground wires not connected to anything. The woodworks of the house were very good but fixing the electricity, heating and plumbing was hopeless.