Well pump tripping GFCI

[admo]

Yes, it would. In fact, the transformer I linked would not even be connected to the truck’s neutral - there’s no place to put it!

But chl pointed out a requirement I didn't realize, I would need an isolation transformer per circuit. I had thought I could protect the entire house breaker panel with a single isolation transformer sitting between my generator inlet and the transfer switch.

The dream in my mind was that the isolation transformer would have replaced having the electrician route all the circuits to be powered by the generator into the transfer switch breakers, it was expensive in billed man-hours.

Still isolation transformer a good solution for running a pump in the field.

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[Maquis]

But chl pointed out a requirement I didn't realize, I would need an isolation transformer per circuit. I had thought I could protect the entire house breaker panel with a single isolation transformer sitting between my generator inlet and the transfer switch.

The dream in my mind was that the isolation transformer would have replaced having the electrician route all the circuits to be powered by the generator into the transfer switch breakers, it was expensive in billed man-hours.

Still isolation transformer a good solution for running a pump in the field.

I respectfully disagree with his conclusion. A transformer could run the whole house up to its capacity limitation. The only downside is the losses associated with a transformer.

 

[shelnian]

I believe the isolation transformer requires over current protection on the load (pump) side as well as the source side. This may mean the feeder breaker (source side) and wiring may need to be increased because of the increased current requirement (transformer plus the pump).

 

[chl]

I respectfully disagree with his conclusion. A transformer could run the whole house up to its capacity limitation. The only downside is the losses associated with a transformer.

Not saying ANY transformer couldn't run a house, just not an isolation transformer whose purpose is, in this case, to isolate the supply ground in the Lightning avoiding GFCI trips.

Code (NEC) requires a properly grounded system in a dwelling, that is a "neutral" connection to ground.

Grounding is essential for safety in electrical systems. It provides a path for fault currents to reduce the risk of electric shock. A fully isolated system may not provide adequate grounding for safety devices like circuit breakers or ground-fault circuit interrupters (GFCIs).

You cannot comply with the grounding requirement AND be isolated by an isolation transformer at the same time.

Anyway, I did not say you couldn't run your whole house off an isolation transformer, only that it would not be up to code due to the grounding requirement.

If it were up to code, providing a grounded "neutral" on the secondary (pick one of the secondary conductors and call it "neutral" and hook it to the neutral wires in your house and ground it at the service panel), that would defeat the isolation and it wouldn't be isolating anymore. It would just be acting as a distribution transformer and a very expensive one because isolation transformers are pricey compared with regular transformers.

Heck, the power company has regular distribution center-tapped transformers in neighborhoods, that's how you get utility power most places. The center tap is your neutral and it is grounded. They are not isolation transformers.

According to the NEC (National Electrical Code), an isolation transformer alone cannot be used to directly power a dwelling; while it provides electrical isolation, it does not meet the necessary requirements for a standard power distribution system in a home due to lack of proper grounding and potential safety concerns related to neutral conductor connection.

According to the National Electrical Code (NEC), the ground path for a transformer powering a home typically involves connecting the transformer's neutral conductor to a grounding electrode (like a ground rod), which then runs to the service panel's grounding bus, effectively grounding the entire electrical system within the house; this ensures a safe path for fault current in case of a ground fault.

But hey, ask an experienced electrician and see what they say about it. I am an electrical engineer not a licensed electrician, but I can read and understand the code and know an ungrounded home could easily be a death trap.

 

[chl]

PS: The specific requirements for grounded neutrals are primarily outlined in Article 250 of the NEC, particularly section 250.184 which covers solidly grounded neutral systems.

Hot and neutral wires are both power carrying wires. One of the power carrying wires is grounded at the source for reasons of safety. The only reason why the two wires are differentiated (hot vs. neutral) is to identify which of the wires is grounded (the neutral wire).


What is the purpose of the neutral wire? The reason that one of the power wires is named “neutral” is because it is connected directly to the building ground connection at the circuit breaker panel. Therefore it is connected directly to the grounding (third) wire. In essence, then, two of the three wires at the wall receptacle are actually grounded wires, one being used for power flow, and the other connected only to exposed metal parts on the equipment. The power wire that is grounded is called the “neutral” wire because it is not dangerous with respect to exposed metal parts or plumbing. The “hot” wire gets its name because it is dangerous.


The grounding of the neutral wire is not related to the operation of electrical equipment but is required for reasons of safety. To reduce the chance of electrical shock, it is important to provide a means to automatically shut down the electrical circuit if an exposed metal part becomes accidentally connected to a hot conductor or circuit. This is accomplished using the 3-wire system by an ingenious technique:

Every electrical circuit is protected by a circuit breaker. One purpose of the circuit breaker is to prevent the building wiring from overheating as a result of excessive user loads being plugged in.

However, in the 3-wire system, the circuit breaker provides another critical safety function.

If a hot wire or circuit were to become accidentally connected to an exposed metal part on a piece of equipment, then a shock hazard would exist.

However, if the exposed parts are connected to the grounding wire, then the hot wire becomes connected to the grounding wire.

This would not cause anything unusual to happen except for the fact that the second power wire, the neutral wire, is also connected to the grounding wire at the circuit breaker panel.

Therefore, the grounding wire essentially becomes connected as a load. The low resistance of the grounding wire causes it to draw a very large amount of current when it becomes inadvertently connected as a load, which in turn causes the circuit breaker feeding the hot wire to trip.

Therefore, the 3-wire system operates in a manner which transforms a safety hazard into an over current condition, causing the safety hazard to be automatically cleared by the circuit breaker. The circuit breaker is used as both an over current protector and a shock hazard protector.

Without a grounded neutral, the breaker would not trip, and the shock hazard would remain.

 

[admo]

Ultimately I'm not going to debate the electrician who comes out, they have been willing to do more stuff to help me with the truck generator stuff but they didn't want to handle a well pump and then the well people were no help at all. This is why I am pleased with the isolation transformer idea because they can certainly do that for me instead of a soft starter.

I will ask them when they come out, although it is clear there is plenty of room for debate on this idea. We are a little rural out here and I'm seeing an uptick in Lightnings around so perhaps this is all helpful for them too.

 

[Maquis]

Not saying ANY transformer couldn't run a house, just not an isolation transformer whose purpose is, in this case, to isolate the supply ground in the Lightning avoiding GFCI trips.

Code (NEC) requires a properly grounded system in a dwelling, that is a "neutral" connection to ground.

Grounding is essential for safety in electrical systems. It provides a path for fault currents to reduce the risk of electric shock. A fully isolated system may not provide adequate grounding for safety devices like circuit breakers or ground-fault circuit interrupters (GFCIs).

You cannot comply with the grounding requirement AND be isolated by an isolation transformer at the same time.

Anyway, I did not say you couldn't run your whole house off an isolation transformer, only that it would not be up to code due to the grounding requirement.

If it were up to code, providing a grounded "neutral" on the secondary (pick one of the secondary conductors and call it "neutral" and hook it to the neutral wires in your house and ground it at the service panel), that would defeat the isolation and it wouldn't be isolating anymore. It would just be acting as a distribution transformer and a very expensive one because isolation transformers are pricey compared with regular transformers.

Heck, the power company has regular distribution center-tapped transformers in neighborhoods, that's how you get utility power most places. The center tap is your neutral and it is grounded. They are not isolation transformers.

According to the NEC (National Electrical Code), an isolation transformer alone cannot be used to directly power a dwelling; while it provides electrical isolation, it does not meet the necessary requirements for a standard power distribution system in a home due to lack of proper grounding and potential safety concerns related to neutral conductor connection.

According to the National Electrical Code (NEC), the ground path for a transformer powering a home typically involves connecting the transformer's neutral conductor to a grounding electrode (like a ground rod), which then runs to the service panel's grounding bus, effectively grounding the entire electrical system within the house; this ensures a safe path for fault current in case of a ground fault.

But hey, ask an experienced electrician and see what they say about it. I am an electrical engineer not a licensed electrician, but I can read and understand the code and know an ungrounded home could easily be a death trap.

I’m quite familiar with the NEC. The transformer I linked to had a 240V primary and a 120/240 center tapped secondary. The center of the secondary winding becomes the neutral which is bonded at the service. The truck sees the load as 240V only, the truck neutral doesn’t get connected anywhere.

The only concern I might have with this setup would be the possibility of transformer inrush current tripping the ProPower on overload.

 

[chl]

Ultimately I'm not going to debate the electrician who comes out, they have been willing to do more stuff to help me with the truck generator stuff but they didn't want to handle a well pump and then the well people were no help at all. This is why I am pleased with the isolation transformer idea because they can certainly do that for me instead of a soft starter.

I will ask them when they come out, although it is clear there is plenty of room for debate on this idea. We are a little rural out here and I'm seeing an uptick in Lightnings around so perhaps this is all helpful for them too.

No debate on isolating the pump - just can't do it for your whole house and be in compliance with code.

Isolation transformers have to be made to high insulating standards so there is no leakage or short between primary and secondary windings so they are more expensive.

The grounded neutral system in homes has been around a long time and provides safety from hot-to-equipment case faults, and GFCI provides additional safety - but GFCI would not work with a floating neutral circuit.

The grounded system provides (in theory) better protection from lightning strikes and surges as well.

So the code has that requirement at least for dwellings.

 

[chl]

I’m quite familiar with the NEC. The transformer I linked to had a 240V primary and a 120/240 center tapped secondary. The center of the secondary winding becomes the neutral which is bonded at the service. The truck sees the load as 240V only, the truck neutral doesn’t get connected anywhere.

The only concern I might have with this setup would be the possibility of transformer inrush current tripping the ProPower on overload.

You did not say whether the truck ground wire is connected to the house.

1) In a 240V single-phase circuit, the 2-pole GFCI does not require an output neutral wire for the load circuit. Instead, one of the hot wires (out of the two hot wires) serves as the returning path for the current, completing the circuit and allowing it to function properly. So any difference in current between the hots will trip the GFCI. So the truck neutral not being connected to the load directly is fine.

2) But...the truck neutral is grounded through bonding to the truck body.

When you ground the secondary center tap you are creating potential ground connection with truck and the neutral of the 240V circuit, i.e., a potential connection to the truck neutral through the bonding and the ground.

Touch the truck body while standing on wet ground, and there would be a ground loop created through your body from the center-tapped grounded secondary of the transformer to the bonded neutral of the truck.

ZAP, current will flow and (hopefully) the GFCI will pop cutting off the current to the transformer primary.

So the "isolation" is gone if you ground the secondary center tap.

So it's no longer an isolation transformer which is supposed to isolate the source and load, by "floating" the secondary output wires from ground (remove the potential of the secondary wires wrt ground) so that touching any one wire of the secondary will not cause a shock. (Still could get a shock from touching both wires of course.)

But grounding the center-tap of the secondary creates a ground reference and a shock hazard, but also a path back to the Lightning bonded/grounded neutral.

I think it is similar to this situation:
Isolation transformers have a case ground and if one output wire of the secondary shorts to the case ground, then only that shorted wire is safe to touch because it is at ground potential. The other wire is a shock hazard.

Assuming the truck output ground is connected to the house ground:
What happens when power is suddenly removed from a transformer? There is a collapse of the magnetic field which will cause a surge of voltage in the secondary - to which your body is still be connected via the center-tap ground and the truck body - without any surge protection.

So much simpler and cheaper to spend $400 on a Generac 6853 transfer switch, inlet and some generator cord to avoid the GFCI tripping.

For a single circuit like the well pump, an isolation transformer is an acceptable solution - without a grounded center-tapped secondary of course..

 

[admo]

You did not say whether the truck ground wire is connected to the house.

I have a neutral switching transfer switch, I am able to power the rest of the house with the truck currently.

So much simpler and cheaper to spend $400 on a Generac 6853 transfer switch, inlet and some generator cord to avoid the GFCI tripping.

Indeed but this number ignores the time, either your own experienced time or an expensive electrician, to route circuits from the main breaker to the transfer switch breaker. I had thought the isolation transformer was a good solution, if it does whole house, because it would skip that re-wiring and be cheaper than more expensive transfer switch after you added man-hours.

But all of this is moot for me, I already have the transfer switch, yet it doesn't handle the pump, so I shall get the transformer installed and be happy with everything working.

I think my electrician was a little scared of this new idea and went a little overboard on the hardware but it worked out in the end (minus the well pump).

 

[Maquis]

You did not say whether the truck ground wire is connected to the house.

1) In a 240V single-phase circuit, the 2-pole GFCI does not require an output neutral wire for the load circuit. Instead, one of the hot wires (out of the two hot wires) serves as the returning path for the current, completing the circuit and allowing it to function properly. So any difference in current between the hots will trip the GFCI. So the truck neutral not being connected to the load directly is fine.

2) But...the truck neutral is grounded through bonding to the truck body.

When you ground the secondary center tap you are creating potential ground connection with truck and the neutral of the 240V circuit, i.e., a potential connection to the truck neutral through the bonding and the ground.

Touch the truck body while standing on wet ground, and there would be a ground loop created through your body from the center-tapped grounded secondary of the transformer to the bonded neutral of the truck.

ZAP, current will flow and (hopefully) the GFCI will pop cutting off the current to the transformer primary.

So the "isolation" is gone if you ground the secondary center tap.

So it's no longer an isolation transformer which is supposed to isolate the source and load, by "floating" the secondary output wires from ground (remove the potential of the secondary wires wrt ground) so that touching any one wire of the secondary will not cause a shock. (Still could get a shock from touching both wires of course.)

But grounding the center-tap of the secondary creates a ground reference and a shock hazard, but also a path back to the Lightning bonded/grounded neutral.

I think it is similar to this situation:
Isolation transformers have a case ground and if one output wire of the secondary shorts to the case ground, then only that shorted wire is safe to touch because it is at ground potential. The other wire is a shock hazard.

Assuming the truck output ground is connected to the house ground:
What happens when power is suddenly removed from a transformer? There is a collapse of the magnetic field which will cause a surge of voltage in the secondary - to which your body is still be connected via the center-tap ground and the truck body - without any surge protection.

So much simpler and cheaper to spend $400 on a Generac 6853 transfer switch, inlet and some generator cord to avoid the GFCI tripping.

For a single circuit like the well pump, an isolation transformer is an acceptable solution - without a grounded center-tapped secondary of course..

Have a nice evening, bye.

 

[admo]

Hey Maquis, thank you for helping me. Right at the beginning in the first reply you got me exactly the information I needed to fix everything.

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