Suspicious Polarity
#1
Member
Thread Starter
Suspicious Polarity
I have an older fridge in the garage, plugged into an outlet with a couple other recepticals on the same circuit. The fridge has worked fine for years and nothing has changed recently. Here's the issue that has me perplexed. My handy-dandy 3-prong plugin tester reports normal polarity at the receptical "before" the fridge but reversed polarity at the receptical "after" the fridge. Opening the receptical boxes, I see nothing wired white to black. The strange part is that if I unplug the fridge, then all the receptacles test normal polarity. In other words, the fridge seems to make the polairty reverse at downstream receptacles!
With the fridge plugged in, voltage at the downstream receptical is 117 V between neutral and ground (sorta confirming the polarity reversal). Unplug the fridge and that voltage drops to 8 volts (really) with 109 volts between between hot and ground or neutral.
Any wisdom out there on what might be the cause of
a). The polarity reversal with fridge plugged in
b). The unusual N-G voltage (8v) with the fridge unplugged
With the fridge plugged in, voltage at the downstream receptical is 117 V between neutral and ground (sorta confirming the polarity reversal). Unplug the fridge and that voltage drops to 8 volts (really) with 109 volts between between hot and ground or neutral.
Any wisdom out there on what might be the cause of
a). The polarity reversal with fridge plugged in
b). The unusual N-G voltage (8v) with the fridge unplugged
#3
Member
Thread Starter
Thanks for prompt reply. I will do more testing to look for an open neutral. However, the N-G voltage drops when I unplug the fridge--can't imagine how that would reconnect the neutral since it is tied together by lugs on the socket. And I have the same issue if I plug the fridge into a different outlet.
Further, my plug-in tester does not report an open neutral when the fridge is unplugged. Is it possible that the fridge is energizing the ground, but not tripping a breaker?
Further, my plug-in tester does not report an open neutral when the fridge is unplugged. Is it possible that the fridge is energizing the ground, but not tripping a breaker?
#4
Member
The problem is probably in the fridge receptacle. Does the fridge actually work?
The voltage is passing through the fridge motor onto the neutral. Since the neutral is open it has nowhere to return.
The voltage is passing through the fridge motor onto the neutral. Since the neutral is open it has nowhere to return.
#5
Member
Thread Starter
Yes fridge works. As do all the other outlets whether or not the fridge is plugged in. Plus, same issue occurs if I plug the fridge into a different outlet.
Did some more voltage testing (fridge unplugged) and found 119 v between hot and neutral (thus, neutral NOT open), 85 volts between hot and ground, 30 volts between ground and neutral. The "first" outlet has a GFCI, but it's wired so the following outlets bypass that protection (i.e. the fridge continues to run when the GFCI is tripped). I'm now suspecting a faulty GFCI. Does that make any sense at all?
Did some more voltage testing (fridge unplugged) and found 119 v between hot and neutral (thus, neutral NOT open), 85 volts between hot and ground, 30 volts between ground and neutral. The "first" outlet has a GFCI, but it's wired so the following outlets bypass that protection (i.e. the fridge continues to run when the GFCI is tripped). I'm now suspecting a faulty GFCI. Does that make any sense at all?
#7
85 volts between hot and ground, 30 volts between ground and neutral.
With a ground issue..... everything will work fine but there will be zero fault protection.
Dennis Miller
voted this post useful.
#8
Member
Thread Starter
Joed: Several outlets report normal polarity when the fridge is unplugged and reverse polarity when the fridge is plugged in. They all work, regardless of whether the fridge is plugged in. As PJ suggests, I'm suspecting a ground issue (rather than open neutral). We'll see what happens when I checkout the GFCI.
#9
In this case you have a ground issue
#10
Member
Thread Starter
Feeling somewhat brainless, here. I left yesterday with my tester indicating reverse polarity. Plugged it in this morning to resume testing and it shows normal polarity. Huh? Turns out the polarity flips NOT when the fridge is plugged in, rather when the compressor engages. Suggests a ground issue with the fridge, but doesn't explain unusual voltages with fridge unplugged.
Last edited by Dennis Miller; 06-28-22 at 11:08 AM.
#11
Not necessarily a fridge problem. Could be the load it presents to the circuit.
A meter would be a better test device.
Those plug in checkers are easily fooled.
A meter would be a better test device.
Those plug in checkers are easily fooled.
#12
Member
Thread Starter
FYI, here is what played out. Multiple issues had me chasing my tail. First, the fridge is most certainly bad. Plugged it into another circuit and it tripped the GFCI. Plugged it into yet another circuit without the GFCI and it tripped the breaker. Yet the fridge worked on the "bad" circuit (though seeming to cause a reversed polarity condition). To unravel the mystery, read on...
I found 2 issues on the problem circuit. First, the groundwire at the fridge receptacle did not have continutity with the ground at the receptacle that fed it. Yet it did show continuity with neutral (and a slight voltage to boot). Turns out the last leg of the circuit is buried, serving a yard light. The second problem was a ground fault on that buried cable. Disconnecting that leg of the circuit returned all voltages to expected values and helped me isolate the ground discontinuity.
I found 2 issues on the problem circuit. First, the groundwire at the fridge receptacle did not have continutity with the ground at the receptacle that fed it. Yet it did show continuity with neutral (and a slight voltage to boot). Turns out the last leg of the circuit is buried, serving a yard light. The second problem was a ground fault on that buried cable. Disconnecting that leg of the circuit returned all voltages to expected values and helped me isolate the ground discontinuity.
#13
I suspect in the old fridge here is a problem that could easily enough be in the old compressor where the neutral is shorted to ground. That would explain why the issue only shows itself when the fridge is plugged in and the compressor is running.