Originally Posted By: apightling This post was automatically imported from our archived forum.
Good question Greg. I don’t take anything for granted. . . they are 1% and I measure them with my Fluke. I also measured the current and verified Ohms laws is still valid . . .
The variable not accounted for is the voltage in the circuit being tested. That I measure on a case by case basis.
Originally Posted By: roconnor This post was automatically imported from our archived forum.
apightling wrote:
I found GFCI receptacles that would not trip at 4.8mA
That would be in the 4mA to 6mA operation range of a GFCI device per the UL standards, and would not be considered defective.
My UL listed plug-in tester measures 18K of resistance between hot and ground when the button is pushed (measured with my UL listed meter of course) ... which would be about a 7mA load on a 120V circuit. That, plus some normal current leakage to ground, should trip the GFCI device within a few seconds.
It does not matter at what current the device does trip within the 4-6mA range, because I am not field checking the device calibration or verifying the device trip curves. You would also have to account for leakage current for it to be an accurate measurement ... sounds pretty sticky, and pretty much useless information for a home inspection.
I would just keep it simple. If a GFCI receptacle doesn't trip from pushing my plug-in tester button for a few seconds (which would be about a 7mA current, plus any leakage) then it gets written up as a defect, and ya move on ... 
apightling wrote:
I also ... verified Ohms laws is still valid . . .
Glad to know that ... I was always worried about that all to simple law of physics ...
-- Robert O'Connor, PE
Eagle Engineering ?
Eagle Eye Inspections ?
NACHI Education Committee
I am absolutely amazed sometimes by how much thought goes into doing things wrong
Originally Posted By: apightling This post was automatically imported from our archived forum.
Robert . . . the few seconds concerns me . . .18K @ 120V is a little less than 7mA. . . any GFCI that I have tested tripped almost instantaneously or not at all . . .
Yep, the 4.8mA may or may not work . . . my Hubbells trip at 4.8mA . . the Levitons next door required more than twice this current . . 'going to go back and hold the button down for a few secs to retest . . .
still, if the path was through a person . . a few secs might be fatal . . .
Originally Posted By: roconnor This post was automatically imported from our archived forum.
apightling wrote:
. . . the few seconds concerns me . . .18K @ 120V is a little less than 7mA. . . any GFCI that I have tested tripped almost instantaneously or not at all . . .
6mA for a few seconds is completely harmless, and within the time/current trip limits in the UL standards for GFCI devices. The trip time rapidly decreases as the current gets above this. This quote is from one of the articles I linked above:
Quote:
When installing and testing GFCIs, you should know that they do not trip instantaneously. In fact, while they typically trip in 25 ms or so at fault currents exceeding 20 to 30mA, they are permitted by UL to take several seconds to trip at fault currents in the 6mA range. This is important to recognize when selecting GFCI testers, for some have timing circuits in them that may limit the test current to a time less than necessary to trip a GFCI.
While most GFCI receptacles will trip almost instantly at around a 7mA current, it could take several seconds and still be completely acceptable and safe according to the UL standards. Do some research on the UL standards, and also check out the device manufacturer's time/current trip curves for a few of the GCFI receptacles.
-- Robert O'Connor, PE
Eagle Engineering ?
Eagle Eye Inspections ?
NACHI Education Committee
I am absolutely amazed sometimes by how much thought goes into doing things wrong
Originally Posted By: jpope This post was automatically imported from our archived forum.
That’s one of the nice things about the SureTest. It provides a 7.4mA “short” and then gives a reading on the time it takes to trip (usually around 120 mS). If the GFCI doesn’t respond to the 7.4mA, the SureTest gives a reading of “Invalid.”
In the case of the GFCI pictured above, it would trip under operation of its internal test button but would not trip when test buttons were depressed on the SureTest and the "three light tester."
In my experience, reliance on the internal test button can be misleading. Even when in the "tripped" position (as in the picture above), this GFCI receptacle was still energized.
-- Jeff Pope
JPI Home Inspection Service
"At JPI, we'll help you look better"
(661) 212-0738
Originally Posted By: jpope This post was automatically imported from our archived forum.
On another note, I think it’s important to “test” more than just the functionality of the GFCI receptacle. Many of the older generation receptacles can be improperly reset.
This one tested to be functional, however, a little manipulation of the reset button shows its vulnerability.
Although this is not true reverse polarity (as indicated by the dummy light), it is an indication that the GFCI can be reset improperly to which I recommend replacement.
-- Jeff Pope
JPI Home Inspection Service
"At JPI, we'll help you look better"
(661) 212-0738
Originally Posted By: roconnor This post was automatically imported from our archived forum.
Jeff … was the receptacle wired correctly? There are situations, like with reverse polarity, where the built-in test button will pop when pushed, but the receptacle may still be live …
I always plug in the GB tester to ensure it lights up with correct wiring first, and then push the built-in receptacle test button to make sure it pops and the tester lights go off. I then reset the receptacle to ensure it lights up with the correct wiring again on reset, then test and reset with the button on the GB tester.
Also, just curious about something with the SureTest. What is the length of time that 7.4mA load is placed on the device before ya get an "Invalid" reading.
-- Robert O'Connor, PE
Eagle Engineering ?
Eagle Eye Inspections ?
NACHI Education Committee
I am absolutely amazed sometimes by how much thought goes into doing things wrong
Originally Posted By: jpope This post was automatically imported from our archived forum.
roconnor wrote:
Jeff ... was the receptacle wired correctly?
The initial test is for proper wiring. Once "Wiring Ok" is indicated, the GFCI can be tested. If it is improperly wired, it will not allow the GFCI test.
roconnor wrote:
Also, just curious about something with the SureTest. What is the length of time that 7.4mA load is placed on the device before ya get an "Invalid" reading.
6500 mS - Here are the steps to an invalid test.
Circuit analysis. . .
GFCI test button applies "short". . .
Result indication. . .
Test duration. . .
-- Jeff Pope
JPI Home Inspection Service
"At JPI, we'll help you look better"
(661) 212-0738
Originally Posted By: roconnor This post was automatically imported from our archived forum.
Okay … so the SureTest would run about 6.5 seconds, at a test “load” to ground of 7.4mA (“short” implies a direct connection of the hot to the neutral). Was curious because the instructions for the GB SureWire indicate to hold the button for up to 6 seconds (per the UL standards for GFCI devices).
That concerned me at first back when I first got the GB tester, as most GFCI receptacles do seem to trip almost instantly with the 7mA load. But a little research at the time indicated otherwise.
I would probably still do a double take anyway if it took more than a second or so to trip ... 
-- Robert O'Connor, PE
Eagle Engineering ?
Eagle Eye Inspections ?
NACHI Education Committee
I am absolutely amazed sometimes by how much thought goes into doing things wrong
Originally Posted By: dandersen This post was automatically imported from our archived forum.
Quote:
In the case of the GFCI pictured above, it would trip under operation of its internal test button but would not trip when test buttons were depressed on the SureTest and the "three light tester."
I find this all the time.
As far as I am concerned, those GFCI's are liars!
How about the ones that trip on the internal test and the power stays on?
Those home made testers don't tell you what's wrong. Just perform a test at the values you built into the tester.
