Total noob trusting an Amish guy plus long distance question

So I read some threads on long distance runs but there are some abbreviations being used I don't understand. I figured out PV meant photovoltaic but anyway...

I bought 8 JA Solar 380w panels, an EG4 3000w 3n1, and 2 48v 100ah lifepo rack style batteries from an Amish guy. This will (hopefully) power a tiny house (skoolie) that has 30amp service with the refrigerator being the only real draw (besides charging phones, the small fan in the composting toilet, and led lighting). The panels will be about 260' (best sun) from the bus. The best I can figure is panels in series, DC from panels to bus (location of EG4/batteries) through (at least) 8 gauge wire.

So many questions - ground rods at both ends? Neutrals and grounds unbonded? Just 2 conductors (no ground) through the conduit?

Thanks!

That Nasally Guy said:

So I read some threads on long distance runs but there are some abbreviations being used I don't understand. I figured out PV meant photovoltaic but anyway...

I bought 8 JA Solar 380w panels, an EG4 3000w 3n1, and 2 48v 100ah lifepo rack style batteries from an Amish guy. This will (hopefully) power a tiny house (skoolie) that has 30amp service with the refrigerator being the only real draw (besides charging phones, the small fan in the composting toilet, and led lighting). The panels will be about 260' (best sun) from the bus. The best I can figure is panels in series, DC from panels to bus (location of EG4/batteries) through (at least) 8 gauge wire.

So many questions - ground rods at both ends? Neutrals and grounds unbonded? Just 2 conductors (no ground) through the conduit?

Thanks!

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Keep in mind, in series, you will be over 300V, and it can be deadly. Use safe practices.

I have 4 strings of 8 Trina375w running over 300' on four pair of 10 AWG XHHW. Voltage is high enough to have minimum voltage drop.
Are you planning to have a separate power shed (need more info for grounding).

Spunky said:

I have 4 strings of 8 Trina375w running over 300' on four pair of 10 AWG XHHW. Voltage is high enough to have minimum voltage drop.
Are you planning to have a separate power shed (need more info for grounding).

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I was going to use an under-bus storage compartment but I'm open to options. The service panel is in one of the compartments and it has a 30a shore power plug in the door.

You don't have to run 8 awg because it's not like a long AC circuit where you have to be concerned about voltage drop. Long solar circuits can drop whatever you want to let them and work fine. It's just losses.

14 awg will lose 5% of your power, 12 awg 3%, 10 awg 2%, 8 awg 1%.

These are not percentages you're likely to notice either way imo.

hwy17 said:

You don't have to run 8 awg because it's not like a long...

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10awg could run another string of 8 panels in parallel to the first 8. Future proofing was my reasoning for mine.

Neutral ground bond at one point, either in the inverter or in an electrical panel. The details that drive this decision depend on the inverter. Primary ground rod located at this bonding point.

Additional ground rod at array optional. There should be a ground wire from the array to the house grounding system. If there is any chance of the array getting a direct lightning strike I would use an additional ground rod there. Not that it will save your panels or equipment, but it might reduce the fire/damage at house side.

That Nasally Guy said:

The panels will be about 260' (best sun) from the bus. The best I can figure is panels in series, DC from panels to bus (location of EG4/batteries) through (at least) 8 gauge wire.

So many questions - ground rods at both ends? Neutrals and grounds unbonded? Just 2 conductors (no ground) through the conduit?

Click to expand...

hwy17 said:

Neutral ground bond at one point, either in the inverter or in an electrical panel. The details that drive this decision depend on the inverter. Primary ground rod located at this bonding point.

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"Neutral" is a term we use for the (usually white) wire of an AC circuit that is nominally zero volts. It should be bonded to ground at exactly one point. For those of us with utility grid connection, it is at the meter or first disconnect.

GFCI breakers or outlets are a good idea for safety.


Because "neutral" was mentioned in a line apparently referring to same PV DC run as the rest of the question, I suspect OP may have meant "negative" PV wire.

Do not bond either PV+ or PV- to anything. If the inverter (or SCC) wants to, it will do so internally.

You should run a ground wire through conduit to PV. It should be sized to carry full current continuously, same as the power conductors. According to NEC, ampacity of PV wires must be at least Isc x 1.56 (vs. x 1.25 for other circuits, because cloud edge effects can make panels deliver more than Isc.)

The reason for ground wire is to connect PV panel frames to inverter chassis. Also connect to ground rod (maybe same ground wires and ground rod as AC circuit, but where an inverter boosts voltage or boosts current, I'd have to think about wire gauge more carefully.)

PV panels can fault to frame, causing DC shock hazard, so need wire back to inverter. Some of these cheap inverters superimpose AC common-mode on PV DC, capacitively coupling to frame and making panels a shock hazard. Or, if panel frames happen to have path to earth ground, the chassis of an RV becomes a shock hazard. Forum members have described this happening.

I agree with the others that PV wire gauge hardly matters for PV. Depending on PV array amperage, could be 12 awg, 14 awg. Doesn't matter if voltage drop is 5%, 25% etc. except for power loss during times of highest production. Voltage drop does matter for battery and AC circuits.

If you have two PV strings, consider two orientations such as SSE and SSW, for reduced peak current but more hours. That can keep battery charged later and start recharging earlier. (Of course optimize for more winter or summer production as needed.)

@Hedges Could be UF-B instead of conduit right? I know it's not popular, but I've been searching for anyone to say you can't. Solar industry mostly just reacts with confusion, cause they're not used to it.

It would work, perform the desired function.

I'm not sure about NEC code requirements.
Like PV wire used with MC connectors, UF is rated for sunlight, moisture, voltage (600V rather than 1000V).

I used UF between PV panel junction boxes 20 years ago (panels came without MC connectors.)
I've used it with plug and socket installed, simply unrolled on the ground. 250' of it through a forest. (Don't do like I did and leave excess length coiled. At least not while also running 30A through 12 awg.)

UF is not flexible like PV wire, so maybe exposed ends getting bent by wind would be a problem? But coarse stranded wire is used coming out of conduit for overhead utility connections.

I think where direct burial wire was previously allowed, either code or local requirements now want conduit, out of concern sharp rocks could pierce insulation. For direct burial, sand backfill serves as warning to someone trenching, also ribbon.

An AC circuit run with direct burial could have 5 mA GFCI for protection, but for DC wires any GFCI is higher current like 1A, good for fire protection but not human safety.

Here's an update. I don't have cell coverage where my bus is located so I'm out of pocket a lot.

I don't have the panels set up yet but I did get the EG4 and the two Rubix 100AH batteries installed and hooked up to the 30A service panel in the bus. After a moment of panic until I realized each battery has an on/off breaker the system fired right up and I now have power in the bus. I even figured out how to set the charging amps to match my generator.

I do have a question concerning grounding. Because of things I learned when hooked to shore power at the RV park we were at last month my neutral and ground is not bonded together in the service panel. The batteries, EG4, and the service panel are in one of the bus' underside storage compartments. I drove an 8' ground rod into the ground next to the bus and attached a wire from the EG4's ground screw to the ground bus in the service panel and a wire from the ground bus to the ground rod. Copastetic?

I plan on driving a ground rod at the PV panels once they're put up but you guys seem to be indicating I need a third (ground) conductor in the conduit between the PV panels and the bus?

If you are not connected to shore power, neutral and ground should be bonded somewhere in the system.
Your having added around rod for that system is good.
Yes, there should be a third (ground) conductor from the system to PV panel frames.

Since I'm in the woods I like you notion of UF on the ground. It seems it would be cheaper and easier.