GFI Circuit

[Guest]

Re: GFI Circuit

Originally posted by pierre:
<snip>If the GFCI is tripping, something is wrong!!! <snip>

OK, Pierre now you've got me thinking and this is probably not a novel idea. It sounds like some devices need a "tare" leakage. Like computers. If they leak "1" and the normal threshold is "5", then the fault threshold should be turned up to "6" for computers? Within reason it would be helpful to turn up the fault threshold. Of course there has to be a fault threshold ceiling-- at the point where a device becomes absolutely unsafe.

What if GFCI's were "auto-setting"? When you first plug in a device there would be an indicator on the device telling the GFCI what level to set the fault threshold.

It would be like in cameras that auto-sense the ISA (speed) of the film cartridge. When you plug in the device it would tell the GFCI "I'm a two" and the fault threshold would be set a seven instead of five. That would minimize nuisance tripping.

Or, maybe GFCI should be just be integral to every device like they are on hair dryers, etc.

Just thinking out loud here. You've probably already heard it one hundred times. Thanks for listening.

[ September 20, 2003, 08:50 PM: Message edited by: awwt ]

 

[don_resqcapt19]

Re: GFI Circuit

Wayne,
Just because the device in use has some amount of leakage, doesn't mean it would be safe to raise the trip limit. The 5 mA trip was selected because about 97% or 98% of adult males can let go of the device when being shocked at that level. A lesser percentage of females and children can "let go" at that level of current. Any increase in the trip point will decrease the safety of the device.
Don

 

[Guest]

Re: GFI Circuit

Originally posted by don_resqcapt19:
<snip> Any increase in the trip point will decrease the safety of the device.
Don

Understood. With that in mind the solution would be to LOWER the trip point, but have it go up a tick or two for each leaky device. Turn it down to 3 or 4, but allow it to go to 5 or 6 for leaky devices. That would be a step forward in the technology.

../Wayne C.

PS: This suggestion is for discussion purposes only.

[ September 20, 2003, 10:23 PM: Message edited by: awwt ]

 

[hurk27]

Re: GFI Circuit

Tom
I don't think the problem in refrigeration equipment is because of leakage, from what I have experience is the transient spike when the compressor kicks off. it is at this time when the GFCI trips this is also true of washers as the are common to trip just as the washer fill valve turns off as this is where the timer stops.
I think that what happens is the spike produced is just in half of the cycle and this would show an imbalance in the current transformer in the GFCI causing it to trip. when a point of use surge suppressor is used it solves the problem. With computer monitors it could be the harmonic current from the switching power supply that could be causing a higher or lower frequency in the circuit which would be out of sinc with the supplys 60 Hz. this would show up as a imbalance the same way.

 

[hurk27]

Re: GFI Circuit

If you want to see this event just take a quad-trace osccloscope with data hold and connect it between the l/n, l/g n/g you will only use three of the channels but it will show the spike on eather the l/g trace or the n/g trace but not both as it is too fast to show up on both this will imbalance the current coil in the GFCI just like a ground fault.

[ September 23, 2003, 10:33 PM: Message edited by: hurk27 ]