The inverter detects the voltage between PV+ and PV- to ground and calculates the resistance between PV+ and PV- to ground. If the resistance on either side is lower than the threshold, the inverter stops
Troubleshooting Low Riso on your solar inverter? Learn what low isolation resistance means, what causes it, and how to fix it.
When the solar panels or DC cables and joints are damaged or the insulation layer is aging, the problem of low insulation resistance is easy to occur.
Depending on the PV module rated power and the real Riso of the modules, a rather small PV system could have low insulation resistances causing the inverter to stay disconnected and not start up.
The inverter will detect the insulation resistance of the positive & negative input to earth before connecting to grid, if the resistance falls below the setpoint, the inverter will not connect to grid and
This happens a lot around here. So, they have installed an SMA 8kW sunnyboy inverter with 20 longi 455 panels in two strings (10 modules each). The inverter is showing error 3501, which
Every time the SolarEdge inverter enters operational mode and starts producing power, the resistance between ground and the DC current-carrying conductors is checked. The inverter displays an
A Low Insulation Resistance Error (039 for Grid-Connected and 302 for Hybrid Inverters) indicates that there could be an Earth Fault in the PV array. This type of fault can appear at different times and
An “RISO error” indicates that the inverter has not connected to the grid and produced energy due to the low isolation resistance. Adjusting the RISO threshold level in transformer-less
One of the tests the solar inverter carries out at startup is insulation resistance testing of the DC circuits. Insulation resistance testing involves measuring the resistance between the bare wires and
PEES Power Systems is a leading provider of advanced energy solutions in South Africa and Africa. We specialize in microgrid systems, solar photovoltaic (PV) power generation, BESS (battery energy storage systems), grid‑tied / hybrid / off‑grid inverters, PCS power conversion systems, EMS energy management systems, BMS battery management systems, lithium‑ion & LiFePO4 batteries, and modular energy storage systems. Our portfolio also includes energy storage containers, energy storage cabinets, containerised power stations, off‑grid power supply systems, backup emergency power, clean energy solutions, new energy storage systems, and green power systems. We offer battery cabinets with integrated BMS, outdoor all‑in‑one storage cabinets, commercial & industrial storage, communication battery cabinets, server racks, and transformer capacity expansion services. Whether you need a small off‑grid system or a zero‑carbon factory solution, our products deliver reliability and performance.
Our modular energy storage solutions range from 20ft/40ft mobile containers to outdoor all‑in‑one energy storage cabinets. We are a leading manufacturer of battery cabinets with BMS, offering communication battery cabinets for telecom, server racks for data centers, and energy storage battery BMS systems. We utilize lithium‑ion energy storage batteries and LiFePO4 batteries for optimal safety and lifecycle. Our stackable design allows flexible capacity expansion, while our grid‑forming technology ensures stable microgrid operation. Whether for distributed PV systems, off‑grid power supply, backup emergency power, or large zero‑carbon parks, our products feature advanced thermal management, PCS and EMS integration, and compliance with South African and international standards. We also provide professional energy storage system installation and after‑sales support, and we help clients navigate energy storage subsidies where applicable.