Solar Installation Series – Part 6

Introduction

Wiring your solar power equipment can be an intimidating task. The equipment is expensive and the risk of fire, or damage to the equipment can be high if improperly wired. In this post I will cover the wiring of the EG4 battery and inverter system, using 6000xp inverters and Wall Mount All Weather batteries.

Make sure you are up to date on this series, as the information will be helpful.
Part 1: Solar Power System – Design and Planning
Part 2: Unique Roof Mounts for Solar Panels
Part 3: Lifting Solar Panels – Innovative Solutions
Part 4: Quick Tips for DIY Solar Panel Installation
Part 5: The Ultimate Guide to Building a Solar Equipment Shed

Equipment

As covered in previous posts, the equipment used are the EG4 6000xp inverters and the EG4 Wall Mount Batteries, which I got as a package deal from BigBattery. The package came with the battery and communication cables, but did not come with any cable management such as conduit boxes. Conduit boxes are available from places like Signature Solar, if you choose to use that for wiring your solar equipment.

I elected not to do the conduit boxes because they were an additional $120-$170 per box depending on whether you got the indoor our outdoor version. That does not include the conduit to connect the boxes together.

EG4 6000xp Inverter

The EG4 6000xp inverter is a solar power inverter that takes in up to 8 kW of solar power and outputs up to 6 kW of AC power. In my case, I have two 6000xp’s, which gives me 16 kW of solar input and 12 kW of AC output.

EG4 Wall Mount All Weather Battery

The EG4 Wall Mount All Weather battery is a 48 V, 280 Ah battery. In this setup, we have three batteries giving us a total of 840 Ah. The batteries come equipped with their own breakers to shut off output if needed. They mount to the wall whether they also sit on the floor or not. These batteries are quite heavy, weighing over 300 lbs each.

Running Wire for Solar Equipment

In order to wire the solar equipment, you first have to run the wires into the building and manage them properly. If you are using the conduit boxes, you just need to run the wires through the boxes. However, I would point out that I’ve noticed how much space these wires can take up, and you may have to run several large tubes of conduit between the boxes to keep from packing too many in a small space. Heat buildup in your battery cables would be the main concern since they will carry the highest current loads.

Since I chose not to use the conduit boxes, I needed to come up with another way to maintain the wires. The building is contained and doesn’t have much walking space in it, so I was less concerned about exposed wires as long as they were secure. For my wire management, I used strut channel on the wall between the battery and the inverters, which ran the length of the building.

PV Wires

I designed and 3D printed two types of wire looms to attach to the strut channel. One loom only carries the wires for the solar arrays. Since I will have four strings of solar, I would need to run eight wires (positive and negative for each string). I designed a simple loom that would keep the solar wires on top of the strut channel. The loom had an upper and lower deck, each with channels for four wires. The channels were designed to fit the solar array wires, so that they snapped in place. The loom attaches via a quarter inch bolt and a channel nut.

Battery Cables

I also used 3D printing to get the battery cables organized. The first problem was the cables coming out of the battery itself. The openings for the cables are at the top on the sides of the battery with negative on one side and positive on the other. One problem I encountered was that the battery communication cables are pre-terminated and the fitting does not fit through the provided hole. So I had to come up with a different solution.

I made snap-in channels for both the positive and negative battery terminal looms. The positive loom also has an additional set of channels in between the battery cables for the battery communication cables (green wire in Figure SI-6-5). For the battery terminal looms, I designed them to bolt into existing holes on the battery because, no one wants to drill holes in batteries!

The battery cables that came with the kit were all one length. Excess cable to would need to be dealt with if I didn’t want to cut the cable (and I didn’t!). The battery wire loom was designed so that it could carry up to four battery cables and four communication lines. They were positioned on the rails with two above each battery and one in between each battery. This gave some flexibility on routing the lines to dissipate any extra cable length.

In Figure SI-6-7, you can see the excess battery cable length accounted for by routing the wire across the top of the battery before being routed up to the inverter above it.

AC Power Out

Up until now, we’ve only talked about DC power coming in from the solar panels. But now we have to address the elephant in the room. AC power or alternating current. It’s a necessary evil considering the whole point of this setup is to power a building and buildings generally run on AC power. It’s really not that bad.

The main point that needs to be made is that the inverters put out 6 kW of power each. If you want to harness a full 12 kW of power, you’ll have to combine those two sources. I decided to use a smaller panel that would connect the two power sources into one source to feed the main panel inside. This gave me some room for expansion as well as added an extra layer of safety with two more breakers.

The AC output lines were kept in conduit, separate from the DC input lines. I ran the liquid tight connectors with the flexible conduit from each inverter to the combiner panel. This made it much easier to run the wire compared to rigid conduit.

Connections

Batteries

The kit came with pre-terminated battery cables, with the exception of the cables that connected to the inverters. For those, I had to buy lugs to fit them and use hydraulic crimpers to attach to the cable. I will show that in the section on inverter connections.

Below are the connections on the master battery’s positive terminal. Notice how the wires are held in place by the 3D printed wire loom

For the battery cables, it does not matter which of the positive ports you plug them into. I just used the ones closest to the wall on the master battery. The communication lines are a different story. The communication line going to the inverter is the top connection, while the bottom two go to the other two batteries. If you had more batteries, they would daisy-chain from there.

On the negative side of the battery is where the main power switch is for the battery. You generally only have to press the power button once, although there is a sequence of powering on your batteries when you have multiple. The only other time you will need to touch this button is during a Rapid Shut Down event. That flips the breaker on the positive side of the battery (see Figure SI-6-9), and the only way to reset it is to power off the battery, flip the breaker back on, then power the battery back on. That is something that is not clear in the instructions. The ID panel is for setting which battery is the master battery, and which ones are not.

Inverter Connections

Connecting to the inverters is pretty straightforward. The EG4 inverters are clearly labeled and the connections are simple with screw type, or in some cases push-in type connectors. Any time you use stranded cable and screw-type terminals, you should use wire ferrules to make sure there is a good connection.

The battery terminal use a lug with a 3/8″ post. Shown in Figure SI-6-14. The cables are 00, but the wires are so fine that I needed to go to a 0000 lug to fit the cables. On the left side of the inverter, the battery communications (pale green wire) are Ethernet cables as are the inverter parallel cables (gray wire). In Figure SI-6-15, the four wires going into the green block are for the rapid shut down system. The red and white pair of wires are for the switch signal, while the red and black wires are the 12 volt power supply for the system.

AC Connections

The 6000xp inverters also come with the ability to add a generator or grid power to them. I don’t have either of those hooked up because my system is off-grid only. The load is where you attach a four-conductor cable. The red and black wires are your hot wires for 240 volt power. Those connect to the breaker. The white wire is neutral and green or plain copper is ground. The inverter creates the ground-neutral bond internally when needed, so you must separate your ground and neutral wires at all points in your system.

Solar (PV) Connections

On the right side of the inverter is where the PV connections are made from the solar strings. Right now I only have two strings on the roof (R1 and R2), but I will add two more strings in the field (F1 and F2). It is recommended that you balance the power inputs between the two inverters. I have R1 and F1 connected to the main inverter, and R2 and F2 connected to the second inverter. Even though the field strings don’t exist yet, I have pre-wired them in the solar equipment building to save some time and effort in the future. They are terminated at the outside maintenance switch panel.

Notice in Figure SI-6-16, there is a ground bus behind the solar strings. That is for grounding equipment and AC power. That is not for the solar strings. Each of the MPPT connections require both the positive and negative lines of that string to be connected there.

Maintenance

Because solar panels create power any time there is sun on them, you need to have a way to isolate your power coming in for safety. If you need to do some maintenance on the system you need a way to safely disconnect your solar power. For this, I installed a maintenance box outside my building where I have two, two-pole switches that can turn off the strings. It is also where I mounted my rapid shut down switch.

Make sure you clearly label your wires and switches. The roof strings are connected to the top switch and the field strings will be connected to the bottom switch when they are installed. This also helps the installation of the future field strings because the wiring going in the building is already done. I just need to make the connections at the switch.

Thank You

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