gfci tripping on 200' run of wire

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domnic

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GFCI tripping 200' run of 10-3 uf wire . due to capacitive coupling . if i use # 10-2 uf with no egc will it work ????????????????????????????????????????????
 
It may reduce or eliminate tripping but will not be code compliant unless you have a likely very rare situation where you don't require an EGC.

How about moving the GFCI protection closer to the load end somehow?
 
Will the 10-2 keep it from tripping? ( not code compliant move gfci i know that )
 
GFCI breaker or receptacle?
If receptacle, just put it at the load. There could be too much cumulative leakage in that long of a run.
 
I think making a MWBC using a 2-pole GFCI breaker with a load neutral and feeding 10/3 UF may have less chance of tripping. That's because the capacitive leakage current to ground on the two phases should cancel out to some extent because their voltages have opposite polarities at any point in time. Whether this adds enough value in your situation to offset the extra costs involved is another question.
 
200' A GFCI works on the inbalance of current on the hot to grounded conductor . on a two wire uf cabel what conductor is higher current ?????? ( capacitive coupling )
 
Modern UF cable includes an EGC, so the GFCI can be tripping on capacitive coupling to the EGC (which doesn't go through the sense coil).

Get rid of the EGC and you eliminate the tripping...but violate code and reduce safety.

You are using 10-3...but which wires in the cable? Are you using hot and neutral symmetric with the EGC, or hot and neutral on one side of the EGC, or are you using all 3 circuit conductors? I assume that if you could use a 10-2, that you have a spare conductor in the cable.

If you select the 'hot' furthest from the EGC does it make a difference?

IMHO the best approach using this length of circuit is to eliminate the GFCI breaker, and instead use a GFCI receptacle or blank face GFCI device.

-Jon
 
domnic said:
200' A GFCI works on the inbalance of current on the hot to grounded conductor . on a two wire uf cabel what conductor is higher current ?????? ( capacitive coupling )
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The AC current through a capacitor is proportional to the AC voltage across it. And so even if the hot and neutral conductors have the same capacitance to ground, there will be significantly higher current through the L-G capacitance than the N-G capacitance on a relative basis. Very little current will flow through the N-G capacitance because the N-G voltage should be quite small. This will cause the current through the line conductor on the GFCI output to be higher than that in the neutral conductor, and it will cause the GFCI to trip if the current through the L-G capacitance it sufficiently large.
 
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synchro said:
The AC current through a capacitor is proportional to the AC voltage across it. And so even if the hot and neutral conductors have the same capacitance to ground, there will be significantly higher current through the L-G capacitance than the N-G capacitance on a relative basis. Very little current will flow through the N-G capacitance because the N-G voltage should be quite small. This will cause the current through the line conductor on the GFCI output to be higher than that in the neutral conductor, and it will cause the GFCI to trip if the current through the L-G capacitance it sufficiently large.
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NO neutral in this circuit !
 
So you have a 2 pole (240V??) circuit fed by a GFCI. However you don't need the neutral. You used a 10-3 UF conductors, so the _cable_ has hot-hot-neutral-EGC?

I'd suggest cheating a bit and running the two hots on the conductors symmetric to the EGC. This probably means 1 hot on the black wire, 1 hot on the white wire, the EGC sitting between them, and the red wire sitting unused off to one side.

This would make the system balanced around the EGC, making the capacitive coupling invisible to the GFCI (because you will see the same current from the black hot to EGC and the 'white' hot to EGC.

On the other hand you might have actual leakage from a cable fault!

-Jon
 
domnic said:
Will the 10-2 keep it from tripping? ( not code compliant move gfci i know that )
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Why do you think not code compliant?

What is it supplying?

If straight 240 volt load problem one problem may be not having a neutral to connect to line side of GFCI at the load end.

Most situations you don't have to have to GFCI protect the entire circuit, just the items that require GFCI protection - most of what is in 210.8 is receptacle outlets are what needs the protection and can be provided either at the beginning of the circuit or at the receptacle - but the GFCI must also be readily accessible, but there are ways to make it closer and still readily accessible.
 
winnie said:
So you have a 2 pole (240V??) circuit fed by a GFCI. However you don't need the neutral. You used a 10-3 UF conductors, so the _cable_ has hot-hot-neutral-EGC?

I'd suggest cheating a bit and running the two hots on the conductors symmetric to the EGC. This probably means 1 hot on the black wire, 1 hot on the white wire, the EGC sitting between them, and the red wire sitting unused off to one side.

This would make the system balanced around the EGC, making the capacitive coupling invisible to the GFCI (because you will see the same current from the black hot to EGC and the 'white' hot to EGC.
Click to expand...

Thinking along the same lines, when using the black and red wires for hots it might be helpful to connect the white wire to the ECG. I think that should provide more symmetrical capacitances than just leaving the white wire floating.
UF-cable-3.png
 
synchro said:
Thinking along the same lines, when using the black and red wires for hots it might be helpful to connect the white wire to the ECG. I think that should provide more symmetrical capacitances than just leaving the white wire floating.
View attachment 2557918
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Just went to look at a piece 3 wire with ground UF cable because I didn't thin your picture looked like what I am used to seeing.

Piece I looked at had black and white as the two outer conductors, the red was next to the black and of course the bare between red and white.

I think they all are typically that way.
 
winnie said:
OP asked:



10-2 without an EGC is not compliant.

On the other hand 10-2 with EGC but without a neutral is perfectly fine for a straight 240V load.

Jon
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I thought he was saying placing the GFCI at the load end of the run was what wasn't compliant and that is what I was asking about. Very few cases would it have to be at the supply end of a circuit outside of maybe some art 680 or 682 applications.
 
kwired said:
Just went to look at a piece 3 wire with ground UF cable because I didn't thin your picture looked like what I am used to seeing.

Piece I looked at had black and white as the two outer conductors, the red was next to the black and of course the bare between red and white.

I think they all are typically that way.
Click to expand...

Was it like this one?

UF-B_cable.png

I guess it all depends on what the OP is using.
 
z = 240v/4mA = 60k; 4 mA low limit of GFI
= 1/(377*C)
C= 44,000 pF ; (0.044uF)
44k/250 ft = 176 PF per foot for UF 10/3 ???? (to lazy to go to the shop with capacitance meter this late/early and measure a roll<G>)

Unless I dropped a zero, methink the tripping NOT due to capacitive current - Unless there are a LOT of higher frequency harmonics. .
 
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