Well pump tripping GFCI

[admo]

It looks like a 240VAC 30A transformer (7.2kVA) would cost in the neighborhood of $1700 and up, and would have to be wired to the house as well.

Wiring a transfer switch like the GENERAC 6853 should not cost too much.

Yes, it looks like you have a big Seimens disconnect/transfer switch and a whole separate breaker box too. Definitely on the expensive side compared to a GENERAC 6853 install.

Although the GENERAC manual is a bit obtusely written, basically the wiring is take the hots and neutrals from the circuits you want to back up and connect them to the corresponding hots and neutral prewired in the transfer switch. You also install a 50A breaker in your main service panel and power to the transfer switch when the utility is on (to power the backed up circuits from the utility).

I still think the isolation transformer would be cheaper. You left out all the breakers you must buy and add to the Generac box, I thought those are like $50 each. Plus that time fishing wire around breaker boxes is not free. The isolation transformer Maquis linked was $700 and I presume the install is much simpler as well as implicitly power the whole panel.

The only downside I'm seeing to the isolation transformer is the power loss people talk about but I have no idea what that loss is in practice.

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[Maquis]

I still think the isolation transformer would be cheaper. You left out all the breakers you must buy and add to the Generac box, I thought those are like $50 each. Plus that time fishing wire around breaker boxes is not free. The isolation transformer Maquis linked was $700 and I presume the install is much simpler as well as implicitly power the whole panel.

The only downside I'm seeing to the isolation transformer is the power loss people talk about but I have no idea what that loss is in practice.

Typical operating losses are 3 to 5% for small dry type transformers. Look for an efficiency curve or data sheet before you purchase. Your electrician can help interpret the data.

 

[Hammick]

Wouldn't replacing your well pump with the appropriate sized Grundfos be the best and least expensive option?

 

[admo]

Wouldn't replacing your well pump with the appropriate sized Grundfos be the best and least expensive option?

That's like a $5,000 option.

 

[Hammick]

That's like a $5,000 option.

Yikes. Must be a big ass pump. The 3/4 hp Grundfos installed at our off grid place was like $750 in 2015.

 

[admo]

Yikes. Must be a big ass pump. The 3/4 hp Grundfos installed at our off grid place was like $750 in 2015.

They appear to be ~$2,000 for a 3/4 hp one now. Also have to run the four different copper wires down a 380 foot well, so a lot of copper. And just professional time.

But these numbers are for my situation at 380 feet, I know pumps get exponentially more expensive as you increase their head lift (depth). If you can pump water out from less than 50 feet I bet it is cheap enough to make that option viable.

Part of the wiring cost was them telling me 30 year old copper wire is not up to code anymore, so if they pull it up they have to replace it even if they send the same pump back down. I would be more worried but we had the water tested a year ago so I'm not worried about leaching, although I don't know why the wires are not up to code anymore.

 

[chl]

I still think the isolation transformer would be cheaper. You left out all the breakers you must buy and add to the Generac box, I thought those are like $50 each. Plus that time fishing wire around breaker boxes is not free. The isolation transformer Maquis linked was $700 and I presume the install is much simpler as well as implicitly power the whole panel.

The only downside I'm seeing to the isolation transformer is the power loss people talk about but I have no idea what that loss is in practice.

No the generac has a breaker panel built in.
You just buy 1 50A breaker about $30 to $50 depending on your panel

Even with the transformer idea, you still have to have a transfer-switch of some kind to avoid back-feeding the utility lines from your source/generator/Lightning.

 

[chl]

They appear to be ~$2,000 for a 3/4 hp one now. Also have to run the four different copper wires down a 380 foot well, so a lot of copper. And just professional time.

But these numbers are for my situation at 380 feet, I know pumps get exponentially more expensive as you increase their head lift (depth). If you can pump water out from less than 50 feet I bet it is cheap enough to make that option viable.

Part of the wiring cost was them telling me 30 year old copper wire is not up to code anymore, so if they pull it up they have to replace it even if they send the same pump back down. I would be more worried but we had the water tested a year ago so I'm not worried about leaching, although I don't know why the wires are not up to code anymore.

Could be the type of jacket on the wires - need to be more moisture water resistant now?
Could be the reason for the ground faults if some of the wire jacket has been infiltrated with moisture.

 

[chl]

As for transformer efficiency and losses, from Quora electricians blog:

Efficiency of Distribution Transformers

The efficiency of distribution transformers typically ranges from 60% to 98%, depending on their design, load conditions, and operating environment. The reasons for not achieving 100% efficiency include:

Copper Losses: These losses occur due to the resistance in the windings when current flows through them. The power lost as heat in the windings is proportional to the square of the current (I²R losses).
Core Losses: These consist of:
- Hysteresis Loss: Energy is lost due to the magnetization and demagnetization of the core material as the AC current changes direction.
- Eddy Current Loss: Circulating currents induced in the core material itself lead to energy losses. Laminating the core helps reduce these losses.
Load Conditions: Transformers are typically designed to operate most efficiently at their rated load. Under light or heavy loads, efficiency decreases due to disproportionate losses.
Other Losses: Additional losses can occur due to stray losses (in nearby conductive materials) and dielectric losses in insulation materials.

 

[chl]

And I still wonder about whether there would some ground loop charge transfer issues with the bonded source (Lightning) and the grounded center-tap neutral of the secondary of the transformer. Transformers always have some small capacitance between the primary and secondary that can pass an AC charge.

I think if you have a ground wire continuous from the Lightning ground wire out to the house ground bus in the panel to which the center-tap secondary neutral is bonded then they would be forced to be at the same potential.

If the ground wire is not connected, I think there could be an electrical potential (charge) difference between the bonded neutral at the truck and the grounded neutral in the panel, which could cause some current flow through the earth ground to/from the Lightning neutral and there could be a ground fault detection at the Lightning GFCI.

But I am not sure about this.

Some reasons a ground at one location can be electrically different from another is the resistance/conductivity of the connection through the grounding rod and wires, the earth at the two locations due to things like mineral content of the ground, etc.

The dotted green line is the potential for a charge difference/voltage difference between the Lightning bonded neutral (on left) and the center-tapped grounded neutral in the house panel (on right).

In theory, the two neutrals at the two grounded center taps should have the same voltage if the grounding is perfect and the earth ground between them is a perfect conductor, but in reality neither of those are perfect.

Even a small voltage difference could result in a GFCI detection at the lightning I believe.

There is always some small capacitance between the primary and secondary of a transformer (so called parasitic capacitance) that can pass AC which would be part of the path for the charge transfer. Even in an isolation transformer, some capacitance will persist.

I don't really know the answer. But if you were going to consider powering your home with a $1700 or more transformer connected to your Lightning, it would be good to know the answer.

 

[admo]

Could be the type of jacket on the wires - need to be more moisture water resistant now?
Could be the reason for the ground faults if some of the wire jacket has been infiltrated with moisture.

Possible, the well people were not helpful so I didn't get to question them much on stuff. They didn't want to figure it out and just wanted to sell me a fuel generator. Basically they had two solutions: new pump or a sell me a generator, they did not entertain any other possible solutions or problem solving.

I can let you know what my electrician says about the transformer and whole house versus branch only. But I get the impression you, Maquis, and others in here are also electricians so I'm not going to try and judge who is right.

 

[admo]

I talked to the electrician today, he had an interesting thought; of course the easiest solution is unplugging the ground wire, though he proposed from the well pump and its controller. When considering the dangers he pointed out that my metal well casing is a huge ground rod.

The only danger I'm guessing is if some other part of the system is the ground path, such as an exposed wire touching a metal pipe where everything returns into the garage.

 

[shelnian]

I think you are over thinking this. The GFCI only trips if the current leaving the Lightning on the hot wires doesn't equal the current coming back on the neutral wire. If the ground wire is connected, then it is the only other path; so if the GFCI trips there is source current coming back on the ground wire. Current can only come back on the ground wire if there some connection between it and the source (Lightning) hot wires or source neutral wire. The secondary side of an isolation xfmr is a separate circuit all together, unless it's faulty, which is unlikely.

 

[admo]

I think you are over thinking this. The GFCI only trips if the current leaving the Lightning on the hot wires doesn't equal the current coming back on the neutral wire. If the ground wire is connected, then it is the only other path; so if the GFCI trips there is source current coming back on the ground wire. Current can only come back on the ground wire if there some connection between it and the source (Lightning) hot wires or source neutral wire. The secondary side of an isolation xfmr is a separate circuit all together, unless it's faulty, which is unlikely.

Well sure an isolation transformer would be a good solution but it cost more than unplugging the wire. I just didn't think it would be safe without a ground wire but he made an interesting point about the well casing.

If I understand removing the ground wire the danger would be a short energizes anything it can find and electrocute people if they touch the energized part. But if it energizes the well casing then problem solved.

 

[shelnian]

Not connecting the ground wire going to the Lightning and not installing a switching neutral generator panel is even cheaper which is why I indicated "A lot of people just don't connect the ground wire" in my first post on this thread. There is almost no chance that the Lightning will become energized if connected with a 50' generator extension cable.
I wouldn't remove the ground wire on the pump circuit because I don't think it will make a difference. The metal water pipes coming from the pump are grounded to the main power panel earth ground rods in most houses.

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