GFCI and other concerns for 1500 foot wiring run

Question

I have the following:

• My house with 400a service
• A pond subpanel 300 feet away from house fed from 100a breaker
• A barn 500 feet from pond subpanel currently run by a 12v offgrid solar system that has become unreliable due to shading during winter and long periods of cloudy days other times. This system draws 5 watts idle, 50 watts with everything on.
• A driveway gate system 1000 feet from barn currently fed from separate grid meter, but power company considers this a "commercial" account, and there are $40 in base charges per month (plus $1 of usage charges). This system draws 30 watts idle, 400 watts with gates actuating.

All of the "feet away" stuff is generally in a straight line starting from the house and ending at the driveway gate.

The $40 base fee from the power company has always burned my britches, and now with the issues I'm having with solar at the barn, I'm thinking it's time to run some power from the house.

Considerations:

I'd like to do this as cheaply and easily as possible, as the main reasons to do it are saving time and money, so the more money and time it takes, the less it makes sense to do...

I like the idea of GFCI protection, mainly for going through the pond. It would be very difficult to go around the pond, so I'm figuring I'll go through it by laying the cable on the bottom. There is already wiring through the pond for a fountain and an irrigation pump. I feel like GCFI is a necessity for this part of the run. So I figured just install a GFCI breaker at the pond subpanel at the start of the run ... well, I read that even runs as long as 300 feet can cause nuisance GFCI trips due to capacitance, and my run after the pond panel is 1500 feet. So how do I use a GFCI breaker to protect people from the pond wiring without having nuisance trips? How do I GFCI in segments? Is the only way using a transformer at each segment to isolate it from the previous segment? Or can I untie the grounds at each segment and use separate grounding rods at each segment, or something like that?

I was figuring I'd just run UF 12/2 in 200-500 ft segments, buried 12" deep and GFCI protected. Rent a little trencher from Home Depot and knock it out in a day. One segment goes all the way to the barn, and I'll tap the run to the driveway gate in several places to add receptacles along the driveway, if nothing else than to provide a places along the run to test for connection in the case of connection issues. But I'll have issues with the GFCI and length again, won't I? I've heard about GFCI Class C that is more resilient, but I can't seem to find these breakers for sale, especially that fit in a standard subpanel (seem to be DIN-rail mounted?).

I think I'll have a good bit of voltage drop: Voltage drop: 19.06 Voltage drop percentage: 15.88% Voltage at the end: 100.94

I'm just not too concerned about the voltage drop. Should I be? I know lighting does fine with a voltage drop. Other stuff has done well for me also in the past. I had thought doing the run at 240v do reduce current and step it down with a transformer at the gate, but then I wouldn't be able to tap the run with receptacles, and I'd have to bury 24" per NEC requirement.

What other kind of issues do you see?

Answer 1

There are two huge areas of challenge for this job. #1 the legal way to transit the pond, and I am 100% sure that laying the pipe atop the pond bottom is not allowed, because pipe is not allowed to "leap" underwater valleys as it will have no support. It will also snag any foot traffic. #2 the GFCI capacitance problem as you discuss.

You're also talking quite a staggering sum, even with your shortcutting lowball plan. As such, what keeps hitting my brain really hard is "Revisit Solar". Because the kind of money you'll spend on the wire alone will buy a lot of solar.

The barn system, sounds like it needs to be enlarged or aging batteries replaced.

As for the gate, the need there is not so bad. On one hand, the gate motor - which pulls hard, but only for a few instants. Because of that, the average draw over 5 days is probably less than a watt, and that's what you have to size the battery and panel for. It would really help if you could get a 12V or 24V version of that gate.

I gather the other load out there would be post lights. I would go entirely 12/24V LED for this, and abandon the idea of having the lights burn all night, instead make it only seem that way by strategically placing motion sensors so anyone who approaches finds it on. 12/24V motion sensors exist and are in fact cheaper than 120V sensors. Run 18/3 thermostat cable to them and have them light the light through a relay.

Figure 2 watts average for the gate and 1 watt average for a motion sensor light+sensors, = 3 watts x 10 days reserve = 720 Watt Hours or 60 amp-hours. Very achievable. Put 100W of solar panel on that, aimed straight vertical so snow doesn't stick to it, and if that deosn't suffice add another panel.