Installers typically place four sawhorses on the ground and a thin sheet of plywood on top of the center two horses to provide a workstation. A cordless hacksaw is used to cut the rails to their right lengths. After that, a splice kit of racking hardware is utilized to connect each set of connecting components to make the desired row length. A jumper, which you’ll need to screw onto the rails on either side of the splice, may be included with the kit. This satisfies a code requirement for metal electrical grounding. The rails can then be heaved onto the roof.
After the rails are in place, connect one rail to the next using a short grounding wire, commonly AWG 6 bare copper. The ground wire will eventually be connected to the array’s junction box or combiner. Return to Step 9 of this guide for a refresher on electrical grounding requirements.
Task #8 – Install the microinverters (if applicable), then the modules
The mid-clamps that hold the modules to the rails should be inserted before inserting modules and microinverters. A track may run along the top or side of the rails for this function, depending on the mounting mechanism. Once the modules are in place, the racking literature will describe how to secure the clamps. To ground the modules, an electrical grounding clip (a thin, square piece of stainless steel) must now be put into each other clamp along the row.
If your array includes microinverters, they must be installed on the rails before the modules. Otherwise, you’ll have to consult your designer’s electrical schematic to see how the modules will be connected in a series/parallel configuration (and to the junction box).
If you’re using wire clips to secure the module cables to the rails, be sure they’re installed first. Avoid scratching the glass, crimping the cords, or bumping the modules around too much when moving and installing the latter. Excessive vibration or jarring might cause internal electrical connections to loosen or waterproof seals to detach. As you attach the modules to the microinverter or to each other along the row, the cables should snap together. If you don’t hear the click, move the two cables apart from each other to ensure the connection is secure.
The wires and any other wiring on the array must also be secured to the rails, according to building requirements. The wires should never touch the roof or dangle in such a way that they are dislodged from their connections by the wind. An installer usually twists the long cables once or twice before tucking them into a rail track specifically designed for this purpose. The cables can also be slid into wire clips already attached to the rails.
After everything else is in place, attach the module end clamps at the end of each row, then saw off any additional rail length that isn’t needed. After the cut, make sure to file the metal smooth.
Task #9 – Mount your inverter, junction box and other electrical components
You should know where the junction box or combiner, the microinverter, and any other solar electric system components are located based on your site survey and/or site drawing. The wire between the array and the home’s main service panel is carried by this electrical equipment. The junction box should be adjacent to the array, whereas the inverter and other components are normally installed on the ground near the main panel.
Your electrical components may require plywood backing to support them against a wall, depending on their weight and dimensions. This is especially true of a transformer-equipped central or string inverter. Because this equipment is frequently located outside, be sure the versions you choose have the appropriate enclosure ratings, which are typically NEMA 3 or 4. Furthermore, any disconnects that are installed must be accessible quickly and easily. For example, you wouldn’t want to put one in a locked closet.
A house in Bozeman, Montana, with an inverter and disconnects mounted on the side. Between the components, a half-inch EMT runs. The wire does not crimp because of the wide bends.
This work can be accomplished at the same time as the mounts, rails, and modules are placed, but before the conduit is bent for the wire run, if you have a team of more than 2-3 people.
Task #10 – Install conduit
After leaving the junction box, all wire from the array should be routed through conduit until it reaches the main service panel. Any conduit running along a rooftop, like the modules, should be mounted several inches above the roof. To transport it, you’ll need to install many lifts or mounts.
1/2 inch EMT conduit is typically utilized in a standard installation. This metal pipe is easy to bend with the basic conduit bender and a firm foot due to its tiny diameter. You’ll either bend the EMT or install what’s known as an LB where the wire runs need to pivot (see photo below). Conduit bending, while simple to learn, is a right-brained task, so if you’re having trouble with it, get assistance. That’s because there are no second chances after conduit has been bent.
90-degree bends and offsets are the most frequent curves for a home solar power system. The latter form is a two-turn jog that shifts the conduit path a few inches to the left or right, up or down. Read Klein Tools’ Conduit Bending Guide for more information on this subject.
When cutting conduit using a hacksaw, make careful to use a reamer to smooth off the cut edges. THIS IS A VERY IMPORTANT POINT. During the wire run, a single sharp edge inside EMT conduit may shred wire jackets. Once the copper is exposed, it may come into touch with the metal conduit, resulting in a ground fault. A short circuit occurs when two severed wires come into contact with each other. You won’t realize there’s a problem until the PV system is up and running in either instance.
Conduit fittings that are attached with two sets of channel locks link separate lengths of EMT conduit.
Clamps and mounts, of which there are various sorts, must be used to secure the conduit to the ceiling and walls.
To avoid water seepage from a hole drilled through the roof, a mount specifically built for roof penetration is employed.
You’ll also need to drill or punch holes in all of your component enclosures, then insert a conduit fitting or sleeve before installing the conduit. To tighten most conduit fittings into position, two pairs of channel locks are required.
Task #11 – Run the wire and make all electrical connections
After the junction boxes, inverter, and disconnects (if any) have been installed and the conduit has been secured, the wire run can begin. To summarize, the more hands available for a wire run, the quicker it will be completed. First, a wire pulling device’s fish tape is fed from the run’s farthest array junction box. Someone will have to manually pull the tape (and later the wire) when it enters and then push it through the other side whenever there is an LB.
The tape eventually reaches the central inverter (if you have one) or the main service panel (if you don’t).
At this stage, 3-5 wires (for one or two arrays/module strings) are attached to the tape, and everything is pushed back up via the conduit to the initial junction box. Someone will have to manually pull the wires from one side of the LB (after removing its back cover), then push the witrd on through the other side wherever there is an LB in the run.
The actual wiring connections should be handled by an electrician or a knowledgeable solar technician. Anyone, on the other hand, can learn how to do this work. Inside the junction or combiner box, inside a central or string inverter (if you use them), inside disconnect boxes (if you use them), and, most significantly, inside the main service panel, the job entails connecting array cables and home runs. Keep in mind that these connections will need to be snug for at least 25 years. Any that are loose can result in energy loss (at best) and an electrical fire (at worst) (at worst). Aside from that, even when the main breakers are switched off, the main panel has enough current running down its bus bar to electrocute someone. As a result, leave the final task to the pros.
Another rule to follow when wiring solar electric systems is to leave the home runs or trunk cable (in the case of microinverters) unplugged until the wire splicing and box connections are finished. The on/off levers for disconnects, the central inverter, and other circuit components should all be turned off until the solar electric system is ready to commission and test. Even when the PV system is turned off, mounted solar modules may be transferring DC current downstream (unless microinverters are employed).
PV and USE-2 wires cannot be run through conduit, as described in the prior instruction. All wiring between the array’s junction box and the main service panel is typically done with AWG 8 or 10 THWN-2 wire. Make sure you’re utilizing the right wire kinds and gauges by consulting your system’s electrical diagram.
Last but not least, rather than being tucked behind the array, the junction box or combiner must be secured into position. While it isn’t necessary to mount it to a rafter, it must be secured to something sturdy. Due to the risk of water seepage, most enclosures cannot be laid flat on their backs. Because a shaded site is preferable than one in the hot afternoon sun, the box should be mounted beneath the modules, snuggled against a rail. You may secure it to the rail as well as the conduit it will pass through this manner.
Task #12 – Affix all required safety/danger labels
Once your circuit is up and running, you’ll need to mark and identify all of the components and device positions in accordance with the NEC and local building codes. Labels are frequently available from the same source as electrical equipment, cables, and wire. You may also obtain labels (with customizable warnings) from Specialty Solar Supply online.
When using microinverters or a monitoring system for a central inverter, make sure to read and follow the instructions that come with it.
Installing a tiny system box in an easily accessible location for the homeowner, then programming and activating the wireless (or ethernet) connection is customary.
What kind of solar panel conduit is used?
Rigid and flexible conduit are the two types of conduit commonly utilized in solar installations. Metallic and non-metallic kinds can be found within each category. Some are UL-listed, while others may be deemed recognized components.
Plastics such as Nylon, polypropylene, and PVC are used to create non-metallic conduit that must meet the same performance criteria as steel but being substantially lighter. Galvanized steel, stainless steel, brass, aluminum, and nickel-plated brass are all options for metallic conduit. Some have a combination of metallic and non-metallic materials, as well as anti-static properties, exterior braiding, and other features.
Is it necessary to run solar wire through a conduit?
9. Picking and Sizing Wires
You’ll be ready to size wire, overcurrent devices (fuses and breakers), and conduit for the circuit once you’ve chosen the brand and model of modules you want to use, sized and configured your array, chosen an inverter model, and chosen all your smaller electrical devices (i.e. combiner or junction box, disconnects, etc.). Always use copper wire in household solar electric installations. Aluminum wire is less expensive, but it corrodes and breaks readily. It’s also inefficient when it comes to conducting electricity.
The following information is commonly required for wire sizing calculations, all of which is covered in this tutorial:
- Configuration of the array (i.e. how many modules are wired in series and the number of series strings).
- The hottest local temperature on record (or what’s known as your region’s “2 percent Average”), as well as the coldest you can expect.
- The several sorts of wire you’ll be working with. (PV wire for the array, bare copper wire for the array ground wire, and THWN-2 for everything else are the three most prevalent in household PV setups.)
When picking wire, it’s also important to choose the right gauge, or diameter. Wire gauges, as shown in the diagram above, correspond to the amount of current you intend to flow through your circuit. In general, the thicker the metal conductor inside the wire jacket is, the more current it can carry without causing a lot of friction and heat.
Consider electrical wire as a hose transporting water to better grasp this. The less pressure there is on the hose to supply the water, the more volume there is inside the hose for the water to flow through. The American Wire Gauge (AWG) system is used to identify wire gauges. The lesser the number, the fatter the gauge, which may seem counterintuitive. Wire can be solid or stranded in appearance. Stranding gives beefier gauges that would otherwise be difficult to bend more flexibility.
Wire is sold by color and by the foot or spool size, in addition to gauge. A spool can be 50 feet long, 500 feet long, or any length in between. In general, three colors are required: black for an ungrounded conductor, white for a grounded second conductor, and green for the equipment grounding wire. (If you live in Europe or use a transformerless conductor, both conductors will be ungrounded, or “hot.”) The color red would be used in place of the white wire. This notifies utility employees and electricians that they are working on an ungrounded circuit.
Before acquiring wire for any electrical project, you or your contractor must learn how to use the wire tables and follow the National Electric Code’s guidelines (NEC). Any installation that does not meet NEC criteria will never be approved by your local building inspector. Because the code is amended every several years, different inspection agencies will always utilize different editions (e.g. 2008, 2011, 2012). Early on in your project, find out which version your local authorities want to enforce.
When it comes to wire, the National Electrical Code (NEC) sets the minimum wire gauge that must be used. You can always go bigger once that’s computed. On the DC side, most home PV is wired using AWG 10 (AWG 6 or 8 if utilizing a combiner box), and AWG 10 or 8 on the AC side. The array’s bare copper equipment ground is typically AWG 6, which is durable enough to survive the elements.
Despite the fact that standard sizes are employed, you must still explain to the inspector how much amperage and volts you expect to be pumped through your system. Furthermore, your wire gauges must be rated for the same or greater ampacity than any fuse or breaker used to control them. The terminals inside the junction box, disconnects, and any other electrical enclosures are all rated to resist a maximum amount of heat or current, as mentioned in the preceding phase. You’ll also need to put up warning indicators on your system that designate various voltages and amperages.
As a result, before planning and installing a solar electric system, you should consult an expert (or employ a licensed contractor). You’ll have to do more math if you opt to do it yourself.
PV wire or USE-2 wire is usually used for the array, and it is not run via conduit. The abbreviation USE stands for “underground service entrance.” It isn’t, however, limited to underground applications. Both USE-2 and PV wire can withstand high temperatures. Their coats are both UV resistant and moisture resistant, so they won’t fade in the sun. PV wire is insulated with a second layer.
On the other side of the junction or combiner box, most installers switch to a less expensive building wire, generally THWN-2 Copper. This cable does not need to be UV resistant because it will be run through conduit. It must, however, be able to tolerate extreme heat and moist conditions caused by condensation. All wiring used in most household PV systems is rated for high ambient temperatures of 90 degrees Celsius. This is the same as 194 degrees Fahrenheit. Most indoor wire is rated to withstand temperatures of up to 75 degrees Celsius.
It is possible to run THWN-2 wire all the way to the Main Service Panel. It can be used for both DC and AC circuits, albeit once your wiring exits the inverter, you may need to switch to a different gauge. This is because once the solar electricity is converted to alternating current, the inverter will change the amps and volts.
Any -2 wire (pronounced “Tack 2”) is typically used for two purposes: damp circumstances and extreme heat. THHN/THWN, a less expensive wire, is available and serves a “either/or” circumstance rather than both. So if the weather is damp but the heat is high, it will function. Because the HH in THHN denotes a 90 degree C rating, it will work if you only have high heat. (HH stands for “Hella Hot!” in installer lingo.)
THHN/THWN is not the same as THWN-2, despite what some suppliers claim. If you try to utilize it in conduit or in a high-heat area, a building inspector will reject your installation. Always check to see if the wire you’re buying is branded “THWN-2,” because you’ll need both a high heat rating and water resistance.
It’s also worth noting that THWN-2 isn’t UV-resistant. That is why, when used outside, it must always be run through conduit.
Having to use conduit for some (and maybe all) of your solar power system wiring is, incidentally, a positive thing. Wire is protected by conduit from being blown around, chewed by mice, or yanked on by little children. Wire, on the other hand, can become quite hot within conduit, which is not a good thing. That’s why finding the smallest gauge that can be used is crucial for building inspectors. Before selecting a wire gauge, solar designers must perform ampacity calculations that account for the extra heat generated by the conduit casing.
Another thing to remember about conduit is that the National Electrical Code (NEC) requires metallic conduit for wire runs inside a home or office. Outside, PVC (polyvinyl chloride) conduit is a less expensive option. The disadvantage of PVC is that it degrades significantly faster than metal over time. For most home PV installations, electrical metal tubing (EMT) is the best option. Despite the higher cost, it will make a much better impression on potential homeowners in 10 or 20 years.
Here’s a schematic from a do-it-yourselfer to help you visualize how a residential grid-tied PV system is wired:
A three-line sketch is what it’s called. It shows the course of the three main wires – the nongrounded conductor, the grounded conductor, and the equipment grounding wire – from the array to the utility meter. (To put it another way, there are two conductors and a ground.) Imagine the array modules on the roof to assist you get your bearings (top of diagram). A junction box is present (far left). The wires that escape it will almost certainly travel down the side of the home.
The rest of the circuit is enclosed by a dashed line. It’s safe to presume that this component of the circuit is at ground level based on the earth ground symbol in the bottom righthand corner. It’s worth noting that the Sunny Boy inverter has a built-in DC disconnect on the input (i.e. array) side. Wires run from the inverter’s other (output) side to the home’s main service panel. The line then continues to the utility meter.
Here’s an overview of Electricity 101 in a nutshell: One conductor (wire) runs from the power source (the array) to the load center (main service panel), while another cable potentially takes the electrons back to their source. As a result, the term “circuit” was coined. The equipment grounding conductor (EGC), the third ground wire, is not connected to the PV circuit. All metal boxes and other electrical hardware are connected to earth ground as a safety element. Electricity “conducts” through the EGC and into the earth only when a live (hot) wire shorts into a metal component. As a result, an equipment ground serves a key role in every circuit despite never being part of its normal operation.
Designers break the system circuit into parts to calculate the wire you’ll need, including types, colors (green for ground, white for neutral, etc.), gauges, and lengths. Then they go over each section’s electrical properties and other variables one by one.
PV Input/Output Circuit (connects the combiner/junction box to the inverter)
The PV Output and Inverter Input circuits are often separated in electrical guides, with the DC Disconnect in the middle. However, because the electrical characteristics of house grid-tied systems are usually the same on both sides of the disconnect, this tutorial will combine the two sections into one.)
Your solar modules include four or five-foot long wires with a positive and negative lead already attached.
PV Wire is the most common wire type on module leads. Snap-in connectors, either male or female, should be included on the two leads to make connecting the modules simple. Make a note of the connector type on the array module you choose for example, MC4 since you may need to buy a few more of these connectors to complete the circuit.
You determined the number of modules to be arranged in series and/or parallel throughout the design portion of this tutorial. Two parallel strings of ten modules make up our sample array. As a result, the wiring schematic and all future calculations will account for this. For the time being, the diagram above depicts a single string of 12 modules. On the module row closest to the combiner box, the negative polarity conductor is marked. The positive conductor, on the other hand, travels from the opposite end of the string, across the top, and into the box. Installers refer to whichever conductor is at the far end (i.e., the conductor that is farthest from the junction or combiner box) as the “home run.” Depending on how you connect your modules, it can be either the negative or positive wire. In this case, the home run is a good one.
As you can see, in order to complete the source circuit, some extra PV wire must be added to the array. You’ll also need to figure out how you’ll connect all of the modules and racks. There are two possibilities:
1. Run an EGC from module to module, rack to rack, and all the way to the junction box. From lug to lug, a robust bare copper wire of AWG 6 solid (not stranded) is used. AWG 6 is a tough wire that can withstand the elements (or a mouse gnawing on it) without breaking. AWG 8 or a thinner PV/USE-2 wire must be encased in a PV wire (or USE-2) jackett if you like. However, bare copper is the most common alternative.
2. Use grounding clips and jumpers to connect the racks and modules. You may achieve the similar result by slipping in small grounding clips (they look like washers) while clamping your modules onto the rails instead of connecting a ground to each module and rail segment. To keep the equipment grounding path uninterrupted, you’ll also insert electrical jumper wires on either side of spliced rails in your racking. Please see the photographs below. After that, all you have to do is connect your bare copper ECG to one of the lugs on each row, then route the same wire to the junction box or combiner.
A Wiley WEEB grounding clip is used with mounting hardware on the left to make a strong connection between the module and the rail. The flat plate with the two little dimples is the clip. A WEEB jumper cable is linked over a rail splice on the right. A stray current will efficiently travel in the desired direction – to ground – if the equipment is connected together in this manner. Watch this video to learn more about how the clips and jumps function.
To ground each row of modules, a bare copper ground wire of AWG 6 is commonly used with lugs. When using WEEBS with jumpers (as described above), you just need to ground each row once before running the bare copper wire to the junction box. This ensures that a roof array is securely grounded in compliance with NEC regulations.
Because USE-2 is less expensive than PV wire, many installers select it for the home run. In terms of ratings and the NEC, both varieties share the same electrical characteristics. Both are UV and moisture resistant, and can withstand temperatures of up to 90 degrees Celsius. PV wire, on the other hand, is double insulated and should last longer than USE-2. It’s now required for systems with a transformerless inverter as well. Because the module manufacturer has already sized the leads (either AWG 10 or 12), sizing for other wire in the PV source circuit can be considered pretty much done for you in terms of gauge selection.
An array that uses microinverters or newer AC modules is a key exception to the guidelines for connecting the PV Source Circuit.
In these situations, wiring is a very different beast.
By the time the current leaves each microinverter or module, you’ll have 240 volts of AC.
You must follow the wiring instructions in the device installation guides and, in some circumstances, install specific mult-wire cables offered by the manufacturer if you choose either approach.
See the Enphase installation manual for additional information.
Always choose the color black when ordering PV or USE-2 wire.
By simply putting a colored piece of tape on either end to indicate the grounded and nongrounded conductors, you can use black for both the positive and negative lead (or positive and negative). Other than black, wire jacket colors contain less carbon and decay faster in the sun, thus they should be avoided on the roof.
Roof array wiring is mainly limited to a single product: AWG 10 PV Wire, which comes in 20-foot rolls from solar equipment providers. You can figure out how many feet you’ll need by measuring the distance between the end of each string and the junction or combiner box. Most of the time, the module lead closest to the box can be immediately connected to it. If the distance is too great, you’ll need to add an extension, which is known as a “near end run.”
When purchasing PV wire, you can choose to have one or both ends fitted with snap-in connections. Consider how your modules and home/near runs will link to one other and to the junction/combiner box, as this will cost you more money but save you time. Because different brands of connectors do not interface, you’ll need to use the same type as your module leads. It’s usually an MC4, but not always.