Hoymiles HMS, HMT Microinverters and DTU Gateways

What it is and where it is used

Hoymiles is a Chinese manufacturer specializing in microinverters. A microinverter is installed under one or two PV modules and converts their energy to AC at that very spot, so there is no long DC field and no central inverter. Each module (or pair of modules) has its own maximum power point tracking.

The lines include the HMS series (two inputs, HMS-600-2T to HMS-1000-2T), the three-phase HMT series (for example HMT-1800-6T) and the DTU-Lite-S, DTU-Pro-S and DTU-WLite-S gateways. They are used on residential and small commercial rooftops, where partial shading, several orientations or the need for module-level monitoring justify this topology.

Hoymiles availability and support depend on the market; confirm them with the brand or its local distributor. For the concept of an inverter, see DC-DC converters and inverters; the comparison of topologies (string, microinverter and optimizer) is in string inverter, microinverter or optimizer.

Other string and hybrid inverter brands with their own guide: Solis inverters, Deye hybrid inverters, Fronius inverters, Growatt inverters and Chint Power CPS inverters.

Microinverter guides are also available for the Enphase IQ8 microinverters.

Variants: HMS, HMT and DTU

The values are those on the Hoymiles HMS-600/700/800/900/1000-2T series page; the nominal output voltage is 230 V with a range of 180 to 275 V and the peak CEC efficiency is 96.7% or 96.5% depending on the model. The HMS-D series, mentioned by the press for Latin America, has its own data sheet.

Data from the Hoymiles product brochure (APAC and Africa, 2024)

The product brochure that Hoymiles publishes for Asia-Pacific and Africa, in English, has tables for more models than the page for the HMS-600 to HMS-1000-2T series. Its output data are for 220, 230 or 240 V with a range of 180 to 275 V; the brochure clarifies on each sheet that the range depends on local grid requirements. The input values differ from those on the page cited above (for example, 2 × 14 A for the HMS-800-2T in the brochure, versus 2 × 12.5 A for the HMS-800W-2T). That is why the input current must always be taken from the sheet for the exact model and region.

Data common to the sheets: nominal MPPT efficiency of 99.8%, nighttime consumption below 50 mW, ambient temperature from −40 to +65 °C and IP67 protection rating. They use natural convection without fans and a high-frequency transformer with galvanic isolation. Communication is Sub-1G and monitoring is done in S-Miles Cloud. The HMT series integrates a grid protection relay and declares VDE-AR-N 4105:2018 and EN 50549-1:2019. The HMS series also declares UL 1741, IEC 61727, IEC 62116 and AS/NZS 4777.2:2020.

AC branch circuits. The sheets give the maximum number of microinverters per branch according to the cable cross-section (2.5, 4 or 6 mm²) and state that local requirements must be consulted. For example, for the HMS-800-2T at 230 V the brochure gives 7, 9 and 11 units; for the HMT-1600-4T, 9, 12 and 16. These numbers depend on voltage drop and on the branch protection, and do not replace the project calculation.

Gateways. According to the same brochure, the DTU-Pro-S communicates with the microinverters over Sub-1G up to 400 m in open field and up to 99 modules. Toward the cloud it has RJ45 Ethernet and 802.11b/g/n Wi-Fi (4G version separate). Toward other equipment it offers an RS485 Modbus RTU port at 9600 bps and a Modbus TCP Ethernet port. It is powered by an external 5 V adapter. It is compatible with the HMS, HMT, MiT and MiS series. It supports zero-export control and export power limiting, local configuration with the S-Miles Toolkit app and remote update. The DTU-Lite-S has Wi-Fi only toward the cloud, plugs in directly, and is compatible with the HMS and HMT series. Both upload data to the cloud every 15 minutes.

Module-level rapid shutdown. For installations subject to the NEC, Hoymiles offers the HRSD-2C device (two modules per device) with a transmitter, which declares compliance with NEC 2017 and 2020, UL 1741 and SunSpec Rapid Shutdown. What is required is set by the electrical code that applies to the installation; see rapid shutdown in PV systems.

Main features

• Two modules per unit. Hoymiles describes the 2-in-1 design as a way to install faster, with individual monitoring of each input.
• Sub-1G communication. The low-frequency radio link with the DTU gateway is meant to keep communication stable, including in commercial and industrial installations.
• Safety. Hoymiles mentions rapid shutdown compliance and an isolation transformer for rooftop installations. What the local standard requires on rapid shutdown is set by the code that applies to your installation; the topic is developed in rapid shutdown in PV systems.
• Grid functions. Reactive power control, with declared compliance with EN 50549-1:2019 and VDE-AR-N 4105:2018. Those are European codes; the grid code that applies at a given site is defined by the utility of the project.

Communications and integration

The microinverters talk by radio to the DTU, and the DTU to the Hoymiles S-Miles Cloud. The DTU-Pro-S has an open-air range of up to 400 m, and Hoymiles recommends an extended antenna if the DTU sits inside a metal enclosure or under a metal or concrete roof. Compatibility between each microinverter model and each DTU must be checked in the data sheet, because Hoymiles’ own documentation marks exceptions between series.

Connecting small installations to the grid follows the requirements of the local utility.

Frequently asked technical questions

• HMS-800W-2T manual and datasheet: Hoymiles publishes the data sheet of each series and the quick guide of each DTU in its download center.
• The microinverter does not report: check the distance to the DTU, its antenna and the DTU network before suspecting the unit.
• Module power greater than the microinverter’s: the output is limited to the unit’s rated value; the ratio is chosen at the design stage.
• It disconnects from the grid: see the inverter disconnects from the grid.

What to verify when specifying a microinverter system

• Module against microinverter. Compare the power, the maximum input voltage (60 or 65 V depending on the model) and the module short-circuit current with the microinverter input. Today’s high-power modules can exceed the current of an input; Hoymiles’ table of commonly used modules is a guide, not a guarantee.
• AC circuit. In this topology the long wiring is AC, with several microinverters per branch. The maximum number per branch and the branch protection are given by the manufacturer and by the local electrical code.
• Grid voltage. The nominal output is 230 V with a range of 180 to 275 V in the HMS-2T series of the cited sheet. If the grid at the site is 120/208 V or another voltage, the matching variant of the series must be chosen, which has its own sheet.
• Grounding and surge protection. A microinverter array still needs equipotential bonding of the structures and surge protection on the AC side.
• Maintenance. Replacing a microinverter means roof access; the design must provide safe access paths.

How we help

Our work on an installation with microinverters is the grid connection: interconnection studies, protection and utility requirements, if the project requires them because of its size. For larger plants, the commissioning of solar plants covers transformer stations, substation and protection. To define the connection of your project, see interconnection studies. Field work is done in Colombia, or elsewhere on request. Write to us through the contact page.

Related guides

• DC-DC converters and inverters
• The inverter disconnects from the grid
• String inverter, microinverter or optimizer
• Rapid shutdown in PV systems
• Enphase IQ8 microinverters: IQ8M, IQ8A, IQ8P and Gateway

References

• Hoymiles, product page for the HMS-600/700/800/900/1000-2T, DTU-Pro-S data sheet and download center.
• Canal Solar, article on the HMS-C and HMS-D series.
• EN 50549-1:2019; VDE-AR-N 4105:2018; IEC 62109-1 and 62109-2; IEC 62116.

Frequently asked questions