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Author Topic: GFI's Tripping  (Read 1041 times)

Steve Garris

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Re: GFI's Tripping
« Reply #10 on: October 30, 2017, 06:49:09 pm »

When you say things were being plugged in, does this include bass amps and keyboards being plugged into the PA?

This may be an opportunity for a poor man's distro.  I do a couple outdoor venues each year where I have to run from GFCI Edisons.  Run things back to my PMD and never had any trip issues.  I even have separate GFCIs on my backline stringer so there are two in series with various tube amps plugged into them.  Still no issues.

The first time I tripped it the bands had not arrived yet. I tripped the others while bands were setting up, plugging in to my power strips.

I'm also thinking about the "poor mans distro" idea. Just not sure how to do it but I'm assuming I can find the info online.
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Steve Garris

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Re: GFI's Tripping
« Reply #11 on: October 30, 2017, 06:51:10 pm »

You mentioned power strips. Most have surge suppressors (that donít do much) but do leak some current. Perhaps your power strip is leaking just under the trip current and adding the band gear (which also may leak some) is what is getting you?

I opened up some of mine and snipped out anything that was not an outlet.



Sent from my iPad using Tapatalk Pro

I'm going to plug them all in at my house and see if I can recreate the problem. Thanks!
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Kevin Graf

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Re: GFI's Tripping
« Reply #12 on: October 31, 2017, 09:24:41 am »

Power conditioners can also dump the noise currents into the Safety Ground. Some audio components have leakage currents to their chassis, which is connected to the Safety Ground.
All these noise and leakage currents can add up and trip a GFCI.
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Stephen Swaffer

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Re: GFI's Tripping
« Reply #13 on: October 31, 2017, 12:31:44 pm »

Keep in mind that all GFCI's are not created equal.  In the last 3-4 years there have been significant changes in the requirements they need to meet.  Then, too, standards (as is the case with any code including the NEC) are a minimum-the don't guarantee a quality product.  I guess I could never bring myself to take the cheapest route when it came to a safety device-especially in a mass market/big box scenario.

The main take away form my point is this-you may not be able to duplicate it at home becasue you may have a different brand/vintage GFCI-and the problem could be (and sounds like it is) right on the ragged edge of working.  Ohms law stil applies- and one location running at 114 volts and the other at 124 volts could cause a very small difference.  You really don't have control over that or the GFCI's installed in a venue.  The best policy would be to eliminate as many potential leakage paths as possible.
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Steve Swaffer

Mike Sokol

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Re: GFI's Tripping
« Reply #14 on: October 31, 2017, 07:27:44 pm »

The best policy would be to eliminate as many potential leakage paths as possible.

You can measure the ground leakage on any piece of gear by measuring how much current is flowing through the ground wire of the power plug. However, affordable clamp-on meters typically only measure down to 10 mA which is WAY above the 6mA threshold. One solution is to strip open about 2 feet of a grounded extension cord and wrap the green ground wire 10 times around the clamp jaw. That will create a 10X current multiplier, effectively allowing your $50 clamp meter to read down to 1mA resolution like a $500 meter. I would say that anything leaking more than 1 or 2 mA to the EGC ground wire should be more closely examined.

Kevin Graf

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Re: GFI's Tripping
« Reply #15 on: November 01, 2017, 08:37:16 am »

What are some of the affordable clamp-on meter models that measure down to 10 mA?
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Tim McCulloch

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Re: GFI's Tripping
« Reply #16 on: November 01, 2017, 09:16:34 am »

What are some of the affordable clamp-on meter models that measure down to 10 mA?

You need to measure <10mA.  The current multiplier Mike discusses is the affordable solution if you need a clamp meter solution.  If you can put a conventional meter in line with the EGC wire most any quality multimeter (think Fluke 177) will work.
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Mike Sokol

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Re: GFI's Tripping
« Reply #17 on: November 01, 2017, 03:12:10 pm »

You need to measure <10mA.  The current multiplier Mike discusses is the affordable solution if you need a clamp meter solution.  If you can put a conventional meter in line with the EGC wire most any quality multimeter (think Fluke 177) will work.
That is correct. All you need to do is make a short extension cord with the green-ground wire interrupted and terminated into banana plugs or whatever is needed to plug into your meter. Or you can just use the meter's alligator clips if you like.  Here's the resolution that a Fluke 117 will measure on the 6-amp and 10-amp current inputs. You'll see that it has 1mA of resolution on the normal 6-amp input which is fuse protected. That means you shouldn't blow up your meter if the piece of gear you're checking develops a line-to-chassis short during the test.

You should probably put a sticker on each piece of gear with the mA current leakage you measure. Most modern gear should be way below 1mA, but the old/vintage stuff could easily be leaking a few mA and still be otherwise operational. Interestingly, Crown states in the engineering specs that their modern iTech amplifiers can leak up to 3mA to ground and still pass QC-Inspection. Remember that ground leakage currents are additive, so it would only take a few leaky stage amplifiers on a single backline GFCI to hit the 6mA threshold and trip.

« Last Edit: November 01, 2017, 03:27:07 pm by Mike Sokol »
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John Roberts {JR}

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Re: GFI's Tripping
« Reply #18 on: November 01, 2017, 04:28:37 pm »

Some of the modern digital amps can have RF filters on mains power cord to keep emissions below acceptable limits. These filters can register as low level leakage between mains and safety ground.

JR
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Jonathan Johnson

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Re: GFI's Tripping
« Reply #19 on: November 01, 2017, 04:55:37 pm »

That is correct. All you need to do is make a short extension cord with the green-ground wire interrupted and terminated into banana plugs or whatever is needed to plug into your meter. Or you can just use the meter's alligator clips if you like.  Here's the resolution that a Fluke 117 will measure on the 6-amp and 10-amp current inputs. You'll see that it has 1mA of resolution on the normal 6-amp input which is fuse protected. That means you shouldn't blow up your meter if the piece of gear you're checking develops a line-to-chassis short during the test.

I'll point out that this may not be an accurate test. If there is leakage, and the equipment is interconnected with other equipment or if the chassis is grounded by other means (such as being in contact with structural steel), then some of the leakage current may find a path to ground other than through the equipment grounding conductor.

For an accurate test, disconnect any audio leads from the equipment and insulate the device from incidental grounding.

(Leakage is a common source of "ground loop hum.")
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