Conduit bending for solar PV installers

What PV work asks of a bender

• EMT on the roof, from the array’s junction box to where the run leaves the roof, often following the racking or the roof edge.
• Offsets and kicks to clear rails, vents, flashings and parapets.
• Parallel runs where two or more conduits go side by side down a wall to the inverter, disconnect and meter.
• 90s and stub-ups into junction boxes, inverters and service equipment.
• PVC underground to ground mounts and detached arrays, bent with heat rather than a hand bender.

Follow the NEC and your AHJ for where and how raceways run on a roof, how conductors are sized, and anything specific to PV systems. This page is about the bending.

Offsets and kicks around racking and obstacles

Most rooftop bends are small: an offset to step over a rail, a flashing or a roof edge, a kick to bring a run off a wall, and a 90 into a box or down the side of the building. All of these are in BendMate’s free version.

Low offsets at steep angles are where the two bends start running into each other on a hand bender’s shoe. BendMate flags those in red or orange before you bend, so you can choose a shallower angle.

Parallel runs to the inverter

When two or more conduits run side by side, each one’s bends have to shift so the run stays evenly spaced through the offset or kick.

• Parallel offsets and parallel kicks (Pro): the marks for each conduit, shifted for the spacing between them.
• The rack builder (Pro): a group of conduits bent through the same offset, 90, kick or saddle, all one size or mixed.
• The free parallel offset calculator on this site: the shift per conduit by the multiplier method, if you’d rather work it out yourself.

Pro is a one-time $5.99, with no subscription.

PVC underground

PVC isn’t bent in a hand bender. It is heated until it is pliable, bent, and held until it cools, or the run uses factory elbows. The offset math is the same as for metal conduit, so the multiplier method gives the distance between bends and the shrink.

BendMate’s bender library covers metal conduit: EMT, rigid, IMC and PVC-coated rigid. For PVC, use the multiplier method in the app or the free calculators on this site, and see the guide to bending PVC with heat for the technique.

Voltage drop and conduit fill on long home runs

Home runs on PV jobs are often long, so voltage drop can decide the wire size. The site’s free voltage drop calculator uses the K-factor formula and finds the smallest wire within 3%. A two-wire DC circuit uses the same formula as its single-phase setting.

The conduit fill calculator works from the NEC’s areas for THHN/THWN-2 wire: 3/4" EMT holds up to 10 10 AWG THHN, and 1" EMT up to 16. PV wire and USE-2 have thicker insulation than THHN, so check their area in the manufacturer’s data.