240V GFCI, No EGC

anthonysolino

Senior Member
Again, great thoughts. It’s nice to be able to bounce this off of some intelligent sources. The more I think about it and read the replies above, I think that indeed a two pole GFCI would work. Looks like the next step is to install one and see if we can create a test.
the only problem you will run in to is keeping every thing at the same potential, your GFCI will function your just in a situation where that circuit may or may not open in the event the motor becomes energized, you might be able to go out there and take that hot wire and touch it to the well motor and weld with it! lol. it will be cool to know the results!
 

LarryFine

Master Electrician Electric Contractor Richmond VA
** the earth shall never be used as an effective fault current path. the EGC is critical

I would concur, I THINK its just a thought that IF a phase landed on the equipment that has NO EGC present, once the load is placed, the GFCI may trip due to the higher resistance thus creating more current on one phase, Then the breaker should function, it wouldn't trip under the notion of a "Dead short" but that of a imbalanced load Due to the increased resistance of the "Dead short" condition. does it seem plausable?
If you say "lower resistance" instead of "higher resistance" then I'll agree with you.
 

anthonysolino

Senior Member
See my post #20.
I would agree with that, thats why I feel the EGC is a critical component in this
If you say "lower resistance" instead of "higher resistance" then I'll agree with you.
I actually think it doesn't matter the condition it being higher or lower, its depends on the impedance characteristics of what ever it is being energized, high or low resistance, if that OCPD sees any difference in current its going to open, but I see your point, though sir,
 

LarryFine

Master Electrician Electric Contractor Richmond VA
I would agree with that, thats why I feel the EGC is a critical component in this
It is in any compliant installation. The OP is asking about decreasing the hazard of an existing situation.

I actually think it doesn't matter the condition it being higher or lower, its depends on the impedance characteristics of what ever it is being energized, high or low resistance, if that OCPD sees any difference in current its going to open, but I see your point, though sir,
Reducing resistance increases current for a given voltage.

In this forum, it's risky to agree with mis-statements.
 

GoldDigger

Moderator
Staff member
The OP specifically asks about the situation of a 240 V double pole (two hot wires) circuit breaker with no connection to either ground or service neutral. I have not seen any that will work without power to the internal electronics.
But it should not be installed that way.
A properly installed GFCI circuit breaker at a panel with accessible neutral will protect the OP's two wire circuit. A GFCI breaker installed at the far end of a two wire feeder cannot work without an accommodation such as a control transformer to drive a virtual neutral to power the breaker electronics.

Sent from my XT1585 using Tapatalk
 

480sparky

Senior Member
Location
Iowegia
This was settled 16 years ago, folks.



20 years ago:

 

LarryFine

Master Electrician Electric Contractor Richmond VA
The OP specifically asks about the situation of a 240 V double pole (two hot wires) circuit breaker with no connection to either ground or service neutral.
He said the service, so I believe there is a supply neutral. Let's ask:

Hey, Lioneye, is there a neutral in the panel where this circuit originates?
 

anthonysolino

Senior Member
It is in any compliant installation. The OP is asking about decreasing the hazard of an existing situation.


Reducing resistance increases current for a given voltage.

In this forum, it's risky to agree with mis-statements.
I understand the concept, I was saying, if the circuit decides increase or decrease resistance, that OCPD is going to see a difference of current
again, that is going to depend on the impedance of the well motor frame. could you not agree if that well motor casing was made of gold it would be of a low resistance vs steel where the value would differ, thus change your ampacity values? I don't think any one would disagree or its a false statement,
 

Lioneye

Member
Location
Northwest USA
Occupation
Commercial Electrician
He said the service, so I believe there is a supply neutral. Let's ask:

Hey, Lioneye, is there a neutral in the panel where this circuit originates?
Yes. Standard 120/240 200A resi service at main structure. Neutral, GEC, bonding to metal piping, IBT, EGC to branches in house all verified. They could install a 2-pole GFCI and terminate the device neutral to the grounded terminal. The 240V branch circuit to the well is definitely 2-wire only.
 

hillbilly1

Senior Member
Location
Atlanta,Ga
30-40 years ago, non grounded pumps were the norm. Water lines were generally black plastic, but some drops into the wells were galvanized. Even if there was a ground run, odds are, the pump is not grounded. Normally around here, the well driller would run open twisted conductors to the top of the well, then the electrician would take it from there, or the well driller would continue the pump cable to the house where the electrician would connect. It’s only been the past 20 or so years the well drillers have been grounding the pumps around here.
 

synchro

Senior Member
Location
Chicago, IL
Occupation
EE
From a short term and cost standpoint, I was hoping to gather into to support or dismiss a GFCI solution as opposed to trenching in a new line. Which may happen. Just not an easy task, with distance and rockeries in the way. They may just have to pony up a buck fifty for a breaker and we’ll try it.
Before purchasing a 2-pole GFCI it would be worthwhile to apply 120V on just one of the two pump leads and then measure any AC current that flows. I suggest using a clamp meter first to make sure that the current is relatively low, and if it is then you can apply the 120V through meter leads instead to get a more sensitive reading. If you get more than a milliamp or two then a GFCI is probably not going to work out. It's possible that when 240V is applied to run the pump that the leakages in both conductors could balance out somewhat due to their 180 degree phase relationship. But any increase in leakage on one side will upset the balance, and so such balancing can't be relied on.

If the leakage is around 10mA or less then a GFPE with a a 30mA trip threshold could be another alternative, but they are expensive. This is the cheapest Homeline 2-pole 30A GFPE I could find with a relatively quick search:

30mA is the threshold for personal shock protection in most countries other than North America, where it is 6mA maximum.
If the well casing is metallic then it's very likely to have a significantly lower resistance to the earth in its vicinity than a person touching the well casing would have to this earth. Therefore a relatively small fraction of a 30mA leakage into the well casing should flow into a person touching it. And some of that leakage could also go from the 2-wire cable to earth directly and not into the well casing.
The bottom line is that a GFPE could still be an improvement in safety if a GFCI is not feasible, although a proper ECG would certainly be better.
 

Lioneye

Member
Location
Northwest USA
Occupation
Commercial Electrician
Great insight. I like the method of testing for ma flow. Really I’d like to see a new circuit cable installed, but these are good alternative ideas.
Thanks again, Mike
 

synchro

Senior Member
Location
Chicago, IL
Occupation
EE
Y
You will have have a pretty good amp clamp to measure ma. Most likely if you measure anything it will be too much
I agree. The suggestion was to use an amp clamp first just to make sure that the current was much less than the meter's fuse rating. After confirming that the current is relatively low then the 120V would be applied instead through the meter leads in order to make an accurate current reading. Most meter fuses are good for 10A but I've seen some as low as 2A. These fuses are expensive and very fast acting to protect the meter's electronics. So I'm usually cautious when making a curent measurement through the meter leads, especially on an unknown circuit, to avoid possibly blowing the meter fuse.
 

Jraef

Moderator
Staff member
Location
San Francisco Bay Area, CA, USA
Occupation
Electrical Engineer
Yes. Standard 120/240 200A resi service at main structure. Neutral, GEC, bonding to metal piping, IBT, EGC to branches in house all verified. They could install a 2-pole GFCI and terminate the device neutral to the grounded terminal. The 240V branch circuit to the well is definitely 2-wire only.
If that's the case, then as Larry Fine has said numerous times, it will work and is actually the PREFERRED way of dealing with an ungrounded circuit. The 2 pole GFCI breaker MOUNTED IN THE SERVICE PANEL, only needs the neutral connection to power its own internal electronics. The GF detection is looking at the current going out on one line and coming back on the other one, so if they are not the same by 6mA or more, the breaker trips. Being a 2 pole breaker it is NOT measuring current flow on the neutral nor, contrary to popular opinion, is it monitoring anything on the ground wire. The breaker doesn't actually know if the current is actually going to ground or not, only that not all that goes out is coming back; it just ASSUMES it is going to ground because where else would it be going? So the lack of a neutral or ground wire in the circuit is TOTALLY IRRELEVANT to the GFCI breaker.

Now IF the breaker were in a sub-panel and that sub-panel had no neutral, the breaker would NOT function because its internal electronics would not be powered. The same would be true of a remotely mounted GFCI receptacle (not that there is such a thing for 240V) with no neutral circuit. But that is not the case here, the GFCI breaker is in the service panel where there is a neutral available for it. that's all it needs.

A SINGLE POLE GFCI breaker does need a neutral, because the ENTIRE CIRCUIT needs a neutral. But it too does not need a ground wire.
 
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