Absence of an AC Neutral

Ginlong Technologies (Ningbo) Co. Ltd.

Ginlong Solis USA: 565 Metro Pl. S. Suite 3214, Dublin, OH 43017

Toll free: 866.438.8408, www.solisinverters.com

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Application Note: Ginlong Solis US

Inverters and the ac Neutral

Ginlong Solis US PV string inverters do not require the installation of an ac neutral

Background

UL 1741 / UL 62109 require that PV inverters monitor grid power quality, voltage and frequency so they

can detect abnormal grid conditions and immediately disconnect (and/or ramp down, anti‐islanding). If

the inverter is designed so that voltage, frequency and ac current flow are monitored L1 to neutral and

L2 to neutral, then the UL 1741 standard would require an installer to connect a solid neutral to the

center tap of the distribution transformer (neutral bar in the premises service panel).

However, If the inverter is designed so that a normal/abnormal grid is monitored using both magnitude

and phase measurements of the L1/L2 voltages, and via calculations, an equivalent neutral voltage is

determined, then there is no UL 1741 (SA) / UL 62109 requirement for the installation of a neutral. This

is the design employed by Ginlong Solis US PV String Inverters. In the first half of the power cycle,

power flows from L1 to L2 and in the second half of the cycle, power flows from L2 to L1. Any abnormal

voltage or frequency between L1 and L2 will be detected by the inverter and trip a relay, putting the

inverter into a protected condition.

Ginlong Solis US PV String Inverters; 2.5 kW to 255 kW

The Ginlong Solis US Technical Service Group has thoroughly reviewed the UL 1741 Standard for

mention of the ac neutral in single and multiphase utility interactive inverters. All Solis US single phase

and three phase utility interactive PV string inverters (2.5 kW through 255 kW) are listed on the CEC’s

Grid Support Inverter List and can be installed throughout California and in States that accept the CEC

list of eligible equipment (https://www.energy.ca.gov/programs‐and‐topics/programs/solar‐equipmentlists).

Regarding the installation of Ginlong Solis US inverters, Solis US inverters comply with and demonstrate

adherence to all safety and operations guidance found in both the UL 1741 test standard and the US

National Electrical Code (NEC). Ginlong Solis US single phase PV string inverters are utility‐interactive

inverters with a 2+1 240 Vac inverter output circuit (L1, L2, and PE). Ginlong Solis US three phase PV

string inverters are utility interactive inverters with a 3+1 inverter output circuit (L1, L2, L3, and PE). Per

the PG&E inspection handbook, “the inspector uses the L1, L2, (L3), and ground and/or neutral of the

inverter's ac output circuit for evaluation". A Solis US PV string inverter will demonstrate full

functionality without the installation of a neutral conductor and will be both CEC‐compliant and NEC

2020‐compliant at installation/evaluation.

Ground‐fault detect, arc‐fault detect, the bleeding off of induced voltages and/or small current

imbalances can all be accomplished with the proper installation of a ground (PE) conductor (in addition

to L1 / L2). Installers of Solis US single and three phase inverters must properly install the ground wire

with the AC output circuit. This is important because the ground wire (i.e., PE conductor) is required as;

 a reference to PE (protective earth, Ground)

 equipment shock hazard protection,

Ginlong Technologies (Ningbo) Co. Ltd.

Ginlong Solis USA: 565 Metro Pl. S. Suite 3214, Dublin, OH 43017

Toll free: 866.438.8408, www.solisinverters.com

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Application Note: Ginlong Solis US

Inverters and the ac Neutral

 proper function of the ground‐fault equipment,

 grid interconnection compatibility (ability to respond to abnormal grid, surge withstand

performance, etc.),

 anti‐islanding functionality, and

 protection of the inverter itself.

Ginlong Solis Technical Service Group Research

Ginlong Solis inverter designers recognized that eliminating a neutral would prevent small, shortduration

imbalances in phase switching times from leading to unwanted neutral currents in the output.

Allowing the isolation transformer neutral to “float” prevents these disturbances from causing harmonic

distortion in the host electrical system.

The Ginlong Solis Technical Service Group reviewed sections of the UL 1741 Standard pertaining to;

1. Output power characteristics and utility compatibility (IEEE)

a. All testing (dielectric withstand, output power characteristics, THD, abnormal tests, etc.)

and compatibility simulations can be accomplished with L1 and L2 (and L3 in multiphase

simulations). Ginlong passes all tests without an ac neutral output conductor.

b. Performance

i. Ginlong passes all tests without an ac neutral output conductor

c. Ratings

ii. Ginlong passes all UL 1741 ratings tests without an ac neutral output conductor

d. Markings

iii. Ginlong has all the proper markings per UL 1741

e. Manufacturing and Production Tests

iv. Ginlong inverters can be tested and passes all tests without an ac neutral output

conductor

Ginlong Solis US inverters are CEC listed as eligible equipment for installation. Solis US inverters do not

require a neutral for full compliance with the US National Electrical Code (2017 and 2020). All Ginlong

Solis US inverters meet UL 1741 (SA), demonstrate the latest grid compatibility capabilities and achieve

the highest safety requirements, as set out in the latest harmonized standards.

This technical note has been reviewed in detail by Bill Brooks, PE. and approved as accurate. Mr. Brooks

is a known expert in the field of utility‐interactive PV inverters with 33 years of active experience in the

field and is on the UL1741 Standards Technical Panel and is a member of Code Making Panel 4 of the

NEC that oversees the installation rules related to PV inverters.



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