This article will walk the reader through a real case of a site installation and electrical work.
Table of Contents
This 3.9 kW (15 panels) sunMAX system was divided among two South-facing asphalt composite shingle rooftops (denoted “Subarray 1” and “Subarray 2”). Actual module installation was straightforward, taking less than one day. Site surveys, wire routing, and subpanel installation added more hours to the project. The purpose of this article is to describe the "Rooftop Array Install, providing helpful tips to save time. Then, offer insight into the "Electrical End Run Requirements" through documented system renovations.
Rooftop Array Install
Planning and Preparation
The sunMAX Bill of Materials (shown below) for this project was generated in the sunMAX Design Suite. All sunMAX Materials were therefore ordered and shipped prior to install date, A few additional components were ordered were ordered to account for design changes "on the fly", including:
- Cable Support Clips (SM-CC)
- Mounting Assemblies (SM-MA)
- Panel Connectors (SM-PC)
- Flashing (SM-RM-C)
Note - The BOM generated by sunMAX Design Suite suggests "minimum" quantities of parts based on how the array is laid out. It also assumes arrays are separate/disjoint, which may increase the number and/or type of Jumper & Y-Cables as well as Trim Covers. Refer to the sunMAX User Guide for more tips.
After inspecting the site, materials were purchased from a local Home Depot store for an Electrical End-Run, including raceways/PVC enclosures for wiring/conductor collection.
In addition to the BOM generated by sunMAX Design Suite, a number of tools were brought along to complete the install. A list of tools required for sunMAX installation can be found on Page 4 of the sunMAX User Guide. Additional tooling recommended for a sunMAX install are:
- Impact Driver with 13mm Socket
- Hammer or Stud-Finder
- Wire Hanger (for Finding Studs)
- String for Leveling Mount
Monitoring with Solar Gateway
Before beginning installation of the array the system layout was created in the sunMAX Design Suite to verify the layout on the roof. This layout is also used when and provisioning the system using the sunMAX mobile app. Provisioning is when you tie a specific microinverter/panel to a location in your layout that you designed in the sunMAX Design Suite. Doing this accurately will ensure that the monitoring of the array will be accurate. It is recommended that you scan panel QR codes as the modules are being installed to avoid confusion or access issues.
Measurements and Array Layout
Note - For the purpose of this article, the horizontal direction denotes side-to-side location, vertical denotes up or down the roof slope.
- The installation began by measuring and marking the desired location of the array on the roof. These locating dimensions were referenced from the permit design drawing.
Note - Do not use shingle layers as horizontal guides as they are not necessarily horizontal. Doing such may result in a misaligned array
Note - When marking the roof either chalk lines, chalk sticks, or lumber crayons in contrasting color are recommended.
- Rafter spacing was measured in the attic, which provided a reference point for mounting locations. In this case, the rafters were at a 16” center to center spacing with a few exceptions to account for the house’s HVAC system.
- On the roof using a hammer, one person was able to locate and mark the location of the first rafter from above. All rafters under the array were marked by measuring in increments of 16” from this first location.
Note - It is recommended going across that you measure and mark the location of the gaps between the panels. For a portrait module this is approximately every 40 inches (1015 mm) or for landscape 65 inches (1655 mm). This will aid you in selecting which rafters to use for mounts to identify or avoid situations where connector-mounts (SM-CM) are required.
The rafter closest to the outside of the array markings on both sides was chosen as the first mounting location.
Note - It is important that these mounting locations are located close enough to the edge of the array to not exceed the maximum cantilever dimensions. The Max Cantilever for Portrait and Landscape sunMAX panels are 15.75” (400 mm) and 19.69” (500 mm) respectively.
Note - The Span Tables in Appendix A of the sunMAX User Guide, were used to determine the maximum span between mounting locations with the following site specific parameters.
Ground Snow Load
- Under these conditions the maximum roof mount span of 48” (or 3 rafters in this location) was observed in all roof zones. By working inward from the outside rafter, and using the maximum allowable spacing specified in Appendix A, each of the subsequent mounting locations were identified and marked.
Alignment and Drilling
- Before any drilling was done, a hammer was again used to verify the location of rafters by listening for a solid-sounding thud, compared to a hollow-sounding thud in between rafters.
- As pictured, the Roof Mount has Alignment Notches and Drill Guides to allow for more accurate drilling location and angle.
- The Roof Mount was lined up with the horizontal and vertical chalk marks using the alignment notches on the Roof Mount. Holding the Roof Mount in place with the drill guide holes inline with the rafter, two 3/16” (4.8mm) holes were drilled through each of the Drill Guides approximately 2 inches deep (50mm). It is important that these pilot holes are located within ⅛” (3mm) of the center of the rafter. In cases where a rafter was not hit, a wire-hanger bent at a 90° angle was stuck through the hole to locate the rafter edge.
- The next step in the mounting process was to trim the shingles. The waterproof flashing requires about a 3” radius trimmed around the center of the roof mount. Most of the time, only one layer of shingles needed to be trimmed, but two rows may require trimming for a successful water-tight installation. Guidelines for flashing installation can be found in the sunMAX User Guide Page 16.
Note - It is important that the upper edge of the flashing is obscured by the course of shingles above it. This determine how far down the flashing should be placed when installed.
- Before any trimming was done, a 3” radius was marked around the center of the Roof Mount location with chalk. This circle was most effectively drawn when 3” measurements were taken to the left, right and above the Roof Mount location, and then the semicircle was drawn in by hand.
The next step was to slide the Shingle Ripper (pry bar) under the singles in the flashing installation area to break the bond between the shingles courses and remove any nails that interfered with proper flashing installation.
Note - It is also recommended that you use the shingle ripper on the course above at the same time. Work carefully to avoid damaging the shingles. To remove any nails you can slide the shingle ripper up to the head of the nail and rock it side to raise the nail partially. Then to the course above slide the shingle ripper in and using the hook portion to grab and remove it.
Roof Mounts and Flashing
- The pilot holes drilled into the roof were then thoroughly covered with black roofing sealant. The lag screws and their respective washers were inserted into the roof mount mounting holes and started by hand into the pilot holes. An impact driver with a 13mm socket was then used to tighten each lag screw. It is important not to over tighten the lag screws to prevent damage to the roof materials and/or stripping the rafter.
Note - Be sure to switch between lag screws at least twice while driving the Roof Mount into the rafter. Roofing Sealant should begin to squeeze out from the sides of the roof mount as it is tightened to the rafter.
- After the roof mount was installed, sealant was applied to the underside of the flashing as seen below. The shingle pry was used to hold the shingles up as the flashing slid over the roof mount and into place under the shingles. Note that the Ubiquiti logo on the flashing should be located towards the front.
- A ¼” bead (6mm) of roofing sealant was added over the flashing to cover the gap between the flashing and the roof mount. The Rubber Counter Flashings were then placed over the mount/flashing to complete the roof mount.
Note - There should be enough sealant under the Rubber Counter Flashings to adequately seal the Roof Mount from above. When placing the Rubber Counter Flashings, press down and twist back and forth to evenly distribute sealant underneath.
- Using the shingle ripper to lift the shingle being cut the marked area was cut from shingles allowing enough space to fit the flashing. Tin snips, cutting shears, or a box cutter with a hook blade can be used to trim the shingles. After cutting it is recommended that you slide the flashing in place to make sure no nail interfere and the cutout is correct.
Note - Ubiquiti’s sunMAX mounting systems were engineered with the goal of easy and straightforward installation. The mounting assemblies’ three-directional adjustability allows for on-the-spot adjustments to panel pitch and mounting location.
- To begin, only the bottom row of Mounting Assemblies were installed. The successive rows of Mounting Assemblies were installed in conjunction with the AC Modules. The bottom row of Mounting Assemblies were installed by using the impact driver to fasten them into the roof mount; leaving the screws just loose enough to adjust the mounting assembly position.
- Before installing the solar panels, each row of mounting assemblies needed to be leveled and positioned. Mason’s line was tied to one side of the row, and pulled taut across to the other side. Using a small groove in the mounting assembly, the string provided a straight and level line from one side of the row to the other. Adjustments were made to each mount in the row to ensure a level solar array.
Note - Before installing each mounting assembly, eye-ball check to make sure each mount is at approximately mid-height. This will save time with the leveling process and solar panel placement. Ensure that the white arrow on the mounting assemblies always faces down the roof slope.
After leveling and aligning each mount, the trim skirts were placed on the bottom row. Each trim skirt was secured with the metal Trim Locks.
Note - As the screws for the trim locks are small and easy to drop, take off your gloves to handle them. Placing the trim skirt first helps to keep the mounting assemblies straight and in place for mounting the panels.
- Each AC Module was hoisted to the roof using three people. On the ground, one man would hoist the panel up to the two rooftop installers by sliding it up a ladder. The ladder provided a sliding surface and helped guide the AC Module up to the roof. The Modules were then carried one-by-one to a storage area holding the panels safely away from the workspace.
- Starting with the bottom row, the AC Modules were placed into the mounting assemblies; panel connectors were placed in between each module.
Note - Installing the panel connectors can be tricky; use the arrow & grooves as guides.
- Each AC Module was laid parallel to the roof plane and held in place to install the upper row of mounting assemblies. The Mounting Assemblies for the upper row were clipped into the module frame, aligned, and driven into each roof mount. Panel connectors were also added in between each panel on the upper side of the row, but kept loose to allow for subsequent rows to be added.
Note - When laying the panels parallel to the roof plane, it was helpful to have one person spotting to ensure that the modules were fitting into the grooves of the panel connectors and mounting assemblies correctly.
Y-Cables and Jumper Cables
- Before the AC Modules were hoisted to the roof, the correct Y-Cables (either portrait or landscape) were installed on the Panels by connecting them to the MicroInverter and clipping them into the AC Module frame as shown below. Jumper cables were required to connect between rows of AC Modules. In this case, four jumper cables were required for a five-row system.
- After all panels in a row were securely mounted, the Y-cables between each AC Modules were connected.
Tip - Determine cable path before installing panels.
Electrical End-Run Work
Note - Each residential project will have its own existing electrical infrastructure, requiring specific interconnection design, and possibly the addition of new equipment to accommodate the interconnection. Communication with the homeowner and a certified electrician is essential to saving time and effort during the installation process.
Note - The Electrical work should conform to the Permit plansets you develop with Ubiquiti's Expert Engineer team in the free sunMAX Permit App.
- The geometry and layout of this install site required that a roof penetration method be used to wire the system. Since the arrays were split into two rooftops, each array required its own rooftop enclosure and penetration. Local authorities required that ¾” EMT be used to for the electrical routing. For this install, UL Certified rooftop enclosures were used.
- To install the enclosures, a location near the sunMAX end run was chosen and shingles in that area were cleared. In this case Soladeck 3R Roof Enclosures were used due to their multi-directional conduit access, and grounding and flashing capabilities.
- To penetrate the roof, 1” holes were drilled through the roof in the Rooftop Enclosure Installation area. The Rooftop Enclosure was caulked, and placed in the shingles allowing a ¾” Conduit Nipple to penetrate the roof between two rafters. A short conduit was run from the bottom side of the Roof Enclosures to a small junction box fitted with a watertight cord conductor allowing the Grounding Electrode Conductor to exit for connection to the array. After exiting the junction box, the Grounding Electrode Conductor was routed under the array to the grounding Panel Connector, and held off the roof surface by zip tying to the array. At the grounding Panel Connector, the Grounding Electrode Conductor was stripped and screwed into the Panel Connector grounding lug.
- The four remaining circuit conductors (L1, L2, N, and AC Equipment Grounding Conductor), were then routed to the array End Run via 1/2" conduit from the junction box to the End Run. The Roof Enclosures were grounded to the Grounding Electrode Conductor by the integral ground lugs. The nonmetallic small junction boxes did not required grounding. The 3/4" metallic conduit from each small junction box to each Roof Enclosure was grounded to the enclosed Grounding Electrode Conductor via conduit grounding bushings. These grounding connections are shown in the photos below.
End Run Connector
- As previously mentioned, the AC equipment ground, neutral and two 120V (L1 and L2) homerun conductors for each subarray, denoted by green, white, black and red wires respectively, ran from the small rooftop junction box up to the end run.
- Each wire was stripped at its end and was fastened into its respective terminal on the sunMAX End Run Connector.
Attic Junction Box
- Through the roof enclosures and into the attic, the conduits (each containing three #10 Cu THWN circuit conductors and one #6 Cu Grounding Electrode Conductor) were routed from each array to the Attic Junction Box. The conduit was supported by conduit clamps approximately every 8 feet to meet electrical code.
- Inside the Attic Junction Box, the three pairs of two corresponding #10 circuit conductors from each physical subarray were each spliced into a single #8 Cu homerun conductor using a properly sized wire nut. The two #6 Cu Grounding Electrode Conductors were connected as a continuous main and tap using the Panduit crimping tool and properly sized crimps. The resulting 4-wire End Run Wires ran through a 3/4" conduit from the attic, directly down through an empty wall space, and into the basement for connection to a newly installed auxiliary subpanel. As shown in the photo below, each of the three metallic conduits entering the Attic Junction Box were grounded to the Grounding Electrode Conductor using conduit grounding bushings.
Main Breaker / Subpanel
Note - The existing main and aux panel for this home were full and unable to add an additional breaker for the new solar array. Since this was a 15 panel array, a single 20A 2 pole breaker was required.
- To expand the existing breaker panels, a 100A 6 space Square D Homeline load center was installed adjacent to the existing aux panel.
- To install this new subpanel, an existing 60A 240V 2 pole breaker was relocated from the aux panel to the new subpanel. The new 20A solar breaker was added to the end of the bus (in this case the center of the panel).
Note - It is important that the solar feed breakers are located at the end of the bus or furthest away from the feeds. NEC 705.12(D) requirements governed the size and location of the interconnection equipment.
- To connect the panels a 1-¼” offset nipple was used with ground bushings on each side. A new 80A 2 pole breaker was added to the aux panel in the location of the 60A breaker that was removed. 4 AWG wire was then fed from the new 80A breaker to the feed connection on the new sub panel. The completed subpanel can be seen below.
- For this project, a Panduit T1700 hand crimp tool and listed Panduit grounding crimps were used to make an NEC-compliant connection of the AC Equipment Grounding Conductor to the Grounding Electrode Conductor (as permitted by NEC 690-47(C)) for each physically separated subarray.
Note - The same tool and properly sized crimps were later used in the attic junction box to connect the two subarray Grounding Electrode Conductors into one main (continuous) Grounding Electrode Conductor and one Grounding Electrode Conductor tap, as permitted by NEC 690-47(B).