New GFI on old circuit buzzing. Two of many installed...

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Old 08-20-11, 01:27 AM
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Question New GFI on old circuit buzzing. Two of many installed...

Just installed about 10 GFCI outlets in a 50s home of a friend. Some of the wiring is pretty old, I'd done some new drops from the attic and the new plugs are all 100% fine.

The house is ungrounded (of course, hence the GFCI's on old circuits) but a couple are buzzing.

Two in particular. Others seem to be silent.

I've swapped in other (also brand new) GFCI outlets to test...same result.

Buzzing happens when outlet is operating (green light on) or tripped (test button pressed).

Each outlet has the hot/neutral connected properly to the LINE side of the GFCI and another pair of wires (to another outlet, or other part of the circuit in the house) connected to the LOAD side (downstream protection).

The buzzing happens when I connect all hots/neutrals to the LINE side as well.

Voltage reads fine at 120V...all over the house. (except for one ceiling fixture where the switched hot from a lightswitch reads 60v with the switch off, but the light operates normally as though dead, and the circuit reads 120v with the switch on).

At least two GFCI's are buzzing softly. The house has a new 100amp service installed, they left the old back door panel alone and just turned it into a sub panel, all the circuits off the new main panel are properly grounded etc.

What might be causing this?

3 prong tester reads "open ground" with outlet operating normally... the test button on the tester will not trip the outlet, but the test button on the outlet works fine.

Thoughts, ideas? One of them is near the kitchen sink and the buzzing is slightly audible. We only heard it because of the location. The second GFCI *may* be on the same circuit, it is within 10 feet or so of the kitchen outlet on the other side of a wall around the corner I forgot to check that before I had to leave.

If the second outlet is downstream of the first, a GFCI on it is redundant, but harmless right?
 
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Old 08-20-11, 03:38 AM
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Welcome to the forums! You shouldn't have more than one GFCI on any give circuit to protect all the receptacles in that run. The GFCI should be at the beginning of the run so a to protect all downline receptacles. You will have "open ground" unless the receptacles you have are properly grounded back to the panel. Was new wiring introduced when the new panel was installed, or is the original 2 wire set up still there? The button on the tester should trip the GFCI if it is connected properly. Having more than one GFCI on a circuit will cause nusiance trips and could be the cause of your humming. Redundant, yes. Harmless, yes. PITA, yes. One trips, they both trip, usually, so why have the second one?
 
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Old 08-20-11, 05:18 AM
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thanks! yes most of the house is still 2 wire system... and if the nuisanse humming could be due to harmonics or something caused by multiple GFCI's I will try replacing one of the outlets with a regular plug, after doing a continuity check on the line turned off.

Thanks! any other advice? I love to go at a problem with multiple possible solutions.
 
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Old 08-20-11, 06:50 AM
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Try removing the downstream, load wires from the GFI and see if the buzzing stops. Good chance 2 on the same circuit is the problem.
 
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Old 08-20-11, 08:46 AM
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sorry i forgot to mention, it buzzes even with just the hot (line) wires connected. i checked on two different brand new GFCI's. that kind of changes things.
its not a huge house, but this wall is the one behind the kitchen sink. the wire goes up, then god knows where... what the hell else could be on it interfering? CFL lightbulbs in the kitchen ceiling fixture? do the ballasts insert harmonics or something that the GFCI can't swallow?
the wiring looks ok physically in the box at least...
 
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Old 08-22-11, 06:08 PM
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Open neutral

60 volts would incidicate an open neutral or switched neutral.
 
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Old 08-22-11, 06:40 PM
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60 volts would incidicate an open neutral or switched neutral.
Or a lighted or electronic switch.


Wolfman, Welcome to the forums!
 
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