Application Note: Grounding Optimizers

February 2015
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Grounding SolarEdge Power Optimizers – Application Note
Introduction
PV Systems with module-level electronics (DC-DC power optimizers or micro-inverters) introduce another PV system component
which must be grounded to meet NEC
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requirements. This paper outlines the differing requirements, provides guidelines on how to
properly ground SolarEdge power optimizers and supplies a list of racking models and their appropriate grounding method.
There are two types of grounding connections used in PV systems:

Equipment grounding – Equipment grounding is required for all electrical devices with exposed metal surfaces, as outlined in
690.43-690.46 and, by reference, Table 250.122. Methods for equipment grounding of SolarEdge power optimizers are detailed
in the examples below.

Grounding Electrode Conductor / System Bonding Jumper – not required in SolarEdge systems. In a system utilizing a grounded
array the Grounding Electrode Conductor is required by NEC 690.47-690.48 and 250.168. This conductor provides the bonding
between the grounding system and one of the PV circuit conductors (PV negative or PV positive), and is required to be
contiguous or irreversibly spliced. SolarEdge systems utilize ungrounded PV arrays as permitted under Article 690.35. When
properly installed SolarEdge systems meet the requirements of 690.35, and therefore no Grounding Electrode
Conductor/System Bonding Jumper is required.
Equipment Grounding of SolarEdge Power Optimizers
Use the following power optimizer grounding methods depending on the mounting structures used for the PV system installation.
For full details refer to the SolarEdge Installation Guide.
1 For power optimizers mounted on a grounded metal structure, use the 5/16'' stainless steel grounding star washer (provided
with the power optimizer) between the railing and the flat side of the optimizer mounting bracket. Apply torque of 9.5 N*m / 7
lb*ft.
The star washer is used for attachment of the power optimizer to galvanized steel, stainless steel and anodized aluminum
structures. It penetrates the galvanized or anodized coating of the structure to ensure a low-resistance connection. The star
washer is approved as a listed grounding means in accordance with the requirements of NEC Article 690.43(C).
Figure 1: Star washer
2 If the star washer cannot be used, such as when mounting on some grounded rails with sliding nut fasteners, use the SolarEdge
grounding plate between the railing and the flat side of the optimizer mounting bracket. Apply torque of 9.5 N*m / 7 lb*ft.
The plate penetrates the galvanized or anodized coating of the structure to ensure a low-resistance connection and compliance
with the ground impedance requirements per the UL1741 certification for SolarEdge power optimizers. The grounding plate
may be purchased in bulk from SolarEdge (part number SE-GNDPLATE-100).
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All Code references are to NFPA 70, NEC 2011 Edition.