infinium DSO80604B popping GFI breaker? - Page 1
Forum section: electronics / testgear

author: MarkMoses
author_rank: Newbie
timestamp: August 03, 2022, 05:46:12 pm
content: I have two infinium DSO80604B oscilloscopes, if they are plugged into an outlet on a GFI breaker the breaker will pop, they are fine on a normal breaker?If I lift the ground pin on the line cord it will run like normal on the GFI breaker, but I measure 60VAC on a multimeter from the chassis to ground.Is this normal? Our calibration house says there is no issue with the scope, and they can't repair it.

author: kbrill
author_rank: Contributor
timestamp: August 04, 2022, 04:24:22 pm
content: Switching power supplies and even some inductive ballasts frequently trigger GFI's In my experience this is less common with GFI breakers than with the duplex GFI receptacles . Manufacturers have dismissed this insisting that it is the fault of out of spec or defectively designed devices . I can demo this intermittently but frequently occurring , perhaps 1 in 10 turn on's of T8 florescent fixtures with commercial grade electronic ballast . 1 in three turn on's of inductive single 400 w Hid fixture . Have been told many problems are a result of poor service grounding . My service ground is excellent .ken

author: kbrill
author_rank: Contributor
timestamp: August 04, 2022, 04:38:38 pm
content: There are many reports of new home owners illegally replacing all of the GFI breaker's and receptacles after experiencing frequent tripping and premature failure . I expect this will be far more of a problem with arc fault breakers .

author: wasedadoc
author_rank: Super Contributor
timestamp: August 05, 2022, 09:12:18 am
content: Unlike equipment containing a "heavy metal" mains transformer it is very common for those with switch mode power supplies to have a capacitor from each leg of the mains input to ground. If you open the ground connection the two capacitors form a potential divider and a high impedance meter will show half mains voltage to ground. However the small values of the capacitors should cause the current available to be below the trip current of the breaker. Use you meter set to AC current instead of AC Volts.

author: nctnico
author_rank: Super Contributor
timestamp: August 05, 2022, 09:29:39 am
content: Quote from: kbrill on August 04, 2022, 04:24:22 pmSounds like a quality issue to me. I have lots of equipment connected to a GFI (30mA) and it never ever has tripped spontaneously. GFI operation has nothing to do with grounding; a GFI doesn't even look at the ground wire. Only thing that counts is current difference between line and neutral.

author: mrfrenzy
author_rank: Newbie
timestamp: August 06, 2022, 07:50:45 pm
content: What model is your GFI breaker? Sometimes they are overly sensitive.Your electrician should have an instrument to verify trip current and trip time.(Of course if you know how to safely work with line voltages you could test it yourself)

author: Grandchuck
author_rank: Super Contributor
timestamp: August 06, 2022, 08:01:40 pm
content: A 15 kohm resistor from hot to ground should make the GFI trip. A 47 kohm resistor (or greater) should not. As mentioned, do not mess with it if you do not understand safe procedures.