Sezibwa rooftop solar: panel layout and installer brief

For: the Green Volta installers and the NFE site team. Owner: Aaron Tushabe. Last reviewed: 21 Oct 2026. Status: proposed. The layout was worked out from satellite imagery, so do the site checks below before drilling.

The plan

• What: 8 × Golden Sun GS600N-144M (600 W, 2278 × 1134 mm, 30 kg each), 4.8 kWp in total, from the Muden quote.
• Where: the long north-west-facing face of the house at about 0.36236, 32.53602 (Nansana). The pin 0.36245, 32.53592 lands on the neighbour's roof about 15 m to the north-west.
• How: one row in portrait (long side up the slope), split into two groups of 4 with a 1.5 m gap around a vent or flue. The top edge sits about 0.4 m below the ridge. Flush-mounted at the roof pitch.
• Wiring: all 8 panels in one series string into PV1 of the SRNE ASP48120SH3. PV2 stays free.

Why this roof face

At 0.36° N the sun is close to overhead all year, so the direction a face points makes little difference:

PVGIS (SARAH3 data, 2005 to 2023), 20° pitch, 14% system losses, no tree shade.

The trees decide it. Tall trees stand against the north, north-east and east sides of the house, and big trees to the south and south-west. The north-west face looks away from most of them. All 8 panels are on one string, so shade on one panel pulls down all 8. The north-west face also gives the steadiest output through the year.

Site checks before drilling

Words used in these checks

• Vent or flue. Satellite shows two dark marks about halfway along the face, roughly 8.7 m from the north-east end. If nothing is there, close the gap between the groups to about 0.3 m (keep the two rail pairs separate) and centre all 8 panels on the face.
• Pitch. Measure it and write it on this page. Anything from 10° to 25° is fine.
• Face depth. Eave to ridge along the slope must be at least 3.0 m (2.28 m panel, 0.4 m at the ridge, margin at the gutter). The satellite estimate is about 4.7 m.
• Purlins. Find their positions and spacing. Each rail has to sit on a purlin line.
• Shade.
  • Stand at the array position at about 8 am, noon and 4 pm, or use a sun-path app.
  • Trim the trees on the north, north-east and east sides and on the south and south-west sides to below ridge height.
  • Check that the neighbour's roof (north-west, across the alley) is not higher than our ridge.
• Roof condition. Replace rusty or loose sheets and rotten timber under the array first.
• Cable route. Measure from the drop point to the inverter so the 6 mm² cable can be ordered.

Mounting

The hardware on the Muden quote matches this layout exactly: two 5.1 m rails per group of 4 portrait panels.

• Rail position: rails run parallel to the ridge, about a quarter of the panel length (about 570 mm) in from the top and bottom edges, so about 1.14 m apart.
  • The panel datasheet does not give the clamping zone, so check Golden Sun's installation manual.
  • Move the rails within that zone so they land on purlins.
• L-feet: 3 per 5.1 m rail gives spans of about 2.25 m. Check the rail's span table. 4 per rail (about 1.5 m spans) is safer: that's 4 more L-feet, about 48,000 UGX at the quoted price.
• Fixing: fix the L-feet into the purlins, not just the iron sheet. Go through the crest of the corrugation, with EPDM washers and sealant.
• Airflow: leave about 100 mm under the panels. Cooler panels produce more.
• Load: about 240 kg of panels plus rails, spread over about 21 m².

Wiring: one string of 8 into PV1

The hot and cold figures assume typical n-type temperature coefficients (open-circuit voltage −0.27 %/°C, max-power voltage −0.30 %/°C), because the panel datasheet does not give them.

• Two strings of 4 will not work. They would run at about 155 to 180 V, below the inverter's 200 V minimum. The 4 + 4 split is physical only.
• Panel to panel: panels 1 to 4 connect directly with their 300 mm leads. A short jumper crosses the gap to panel 5, then panels 5 to 8 connect directly.
• Return lead: the string's + leaves panel 1 and its − leaves panel 8, so one lead runs back along the row (about 11 m).
  • Tie it under the panels along the lower rail.
  • Drop both leads at whichever end is nearer the inverter.
  • Keep + and − together all the way to the inverter. A small loop picks up less lightning surge.
• Cable: 6 mm² UV-rated PV cable (the 4 mm² was out of stock). Voltage loss over a 30 m run is under 1%.
• MC4 connectors: crimp them with the proper tool and mate only with compatible connectors.
• At the inverter:
  • The 32 A 4-pole DC isolator, wired to its diagram for 500 V+ DC (usually two poles in series on each polarity).
  • Then the 1000 V DC surge protector, with a short lead to earth.
  • The inverter is IP20, so it must be indoors.
• Earthing: bond every rail and panel frame to the site earth with at least 6 mm² copper.

Not on the Muden quote: bring these

• 6 mm² PV cable for the return lead (about 11 m), the jumper and the run to the inverter. Measure first; 30 to 40 m was budgeted.
• Earthing conductor, lugs or bonding clips, and the connection to the earth rod.
• Roof sealant, EPDM washers, UV-rated cable ties or clips.
• Optional: 4 extra L-feet.

Commissioning

• Before closing the isolator: check polarity and measure the string's open-circuit voltage.
  • Expect about 380 to 425 V in daylight. It reads lower when the panels are hot.
  • About 50 V low means a panel is left out of the string.
  • About 100 V low means one panel is connected backwards.
• Insulation test: if a tester is available, test + and − to earth.
• Close the isolator. Check PV1 voltage, current and power on the inverter display and in OpenEMS.
• Photos: the panel labels and serial numbers (for the warranty), the finished array, the isolator and the surge protector.
• Update this page with the as-built positions, the measured pitch and the voltage reading.

Expected output

Average kWh per day by month, unshaded, north-west face at 20° (PVGIS):

That is about 6,780 kWh a year. It agrees with the 5.2 peak-sun-hour assumption in the sizing re-run (about 19.5 kWh/day). Single days swing a lot with the weather. A month that comes in well below these figures points to shade or a wiring fault.

Assumptions

• Roof dimensions come from Google and Esri satellite imagery, scaled from the Google Maps scale bar, and are good to about ±0.5 m. The pitch is assumed to be 20°.
• The PVGIS figures include no tree shading.
• Sources: Golden Sun GS600N-144M datasheet; SRNE ASP 8 to 12 kW three-phase datasheet V1.0.

Related pages

• Sezibwa solar purchase: final Muden quote (19 Oct 2026)
• Solar Sizing Re-run, Sept 2026 (600 Wp panels)
• SRNE ASP48120SH3 Safe Settings Write: design, registers, and commissioning
• Microgrid Cabinet Line Diagram