Marsun MHD20BM 20 kW Three-Phase Diesel Generator

The Marsun MHD20BM is a 20 kW (22 kW maximum) three-phase (230 V / 400 V, 50 Hz) diesel generator with liquid cooling and a 60 l fuel tank, and it differs from the MHD20B in one respect: operating parameters can be monitored remotely over Modbus. It differs from the MHD20 in having no built-in ATS (a hybrid inverter starts it through the factory Two-Wire Switch connection, or you add a separately bought ATS module) and a 60 l tank instead of 70 l. It suits sites where the generator starts automatically and you want to see its status without going to the unit: homes, farms, businesses and solar systems with batteries. According to the manufacturer, the tank is good for up to 8 hours of continuous running.

Technical specifications

Download the manufacturer datasheet (PDF)

How the MHD20BM differs from the MHD20B and MHD20

Choose the MHD20BM if the generator needs Modbus monitoring. If it does not, the MHD20B is the same generator without Modbus. If you need built-in ATS, a 70 l tank and an additional fuel pump, take the MHD20; if a heated fuel block matters too, there is the MHD20H, which differs from the MHD20 by exactly that.

How much fuel does the MHD20BM use and how long does a full tank last?

The manufacturer states that the MHD20BM has a 60 l fuel tank and can run continuously for up to 8 hours. Use this figure when planning backup power.

A rough calculation from the specific consumption: 204 g/kWh × 20 kW = about 4.1 kg of diesel per hour, or roughly 4.9 l/h (diesel density 0.84 kg/l). By this formula a 60 l tank would last about 12.4 hours at full rated power. This is a theoretical upper limit, not a guaranteed run time: the manufacturer gives consumption as “less than 204 g/kWh”, and real consumption depends on load, temperature and engine condition. The manufacturer provides no additional fuel tank or additional fuel pump for this model.

Automatic start: Two-Wire Switch and optional ATS

The MHD20BM has a factory dry-contact Two-Wire Switch port. It is a simple two-wire connection through which a hybrid inverter or an ATS module can start and stop the generator without anyone stepping in.

• With a hybrid or off-grid inverter. The generator connects to the inverter’s generator input and no extra ATS module is needed. When the battery runs flat, the inverter sends a signal to the Two-Wire Switch port, and the generator takes over the site supply and battery charging.
• Without a solar system. You need a separately purchased ATS module: it monitors the mains, starts the generator when voltage is lost and switches the site’s supply over, then stops the engine and reconnects the mains when it returns.

Closing the contact starts the engine; opening it shuts it down safely. The manufacturer states compatibility with Deye, Solis, Solplanet, GoodWe, Victron Energy and Sungrow hybrid inverters. Connection to the building’s wiring and ATS configuration must be carried out by a certified electrician.

How to connect a generator to a house or site

A generator may be connected to a site’s internal network only through a fixed connection, and the changeover can be automated with an ATS module, which is optional equipment for this model. ESO (Lithuanian grid operator) states:

“A generator may be connected to the internal electrical network of a whole building only by installing a fixed connection and measures that ensure the voltage produced by the generator is not fed into ESO’s networks… Entrust this work only to qualified specialists.”

ESO — Recommendations for installing a backup power source

We handle it for you. We select the equipment for your site, deliver anywhere in Lithuania, install and connect it. We calculate the power you need from your connection and real load, and choose the changeover solution. A consultation before purchase is free.

What to know before you buy

• ATS: not built in. With a hybrid inverter you do not need it; for automatic changeover between mains and generator without an inverter, an ATS module must be bought separately. If you want a built-in ATS from the start, the model with the same output and an ATS is the MHD20.
• Noise: the manufacturer states 72 dB, so think about where to place it near homes.
• Weight and handling: the generator weighs 720 kg and measures 2000 × 900 × 1200 mm. Unload and move it with certified straps or lifting equipment of sufficient capacity.
• Fuel: diesel, 60 l tank. This model has no additional fuel pump, additional tank or heated fuel block.
• Monitoring: besides the frequency and voltage indicator, operating parameters can be monitored remotely over Modbus without going to the generator. This is handy when the generator starts automatically.
• Starting currents: inductive loads such as pumps or compressors draw 2 to 5 times more current when starting than when running.
• Optimal load: running at 100% power for long periods is not recommended; the optimal range is 75–80% of rated power, about 15–16 kW (a 25% reserve).
• Protections: no-load running protection, overcurrent breaker, overpressure protection, smart fuel saving.

Frequently asked questions

How many hours will the MHD20BM run on a full tank?

According to the manufacturer, the Marsun MHD20BM runs continuously for up to 8 hours on its 60 l tank. A theoretical calculation from 204 g/kWh at the full 20 kW gives about 12.4 hours, but for planning you should rely on the manufacturer’s stated run time.

How much fuel does the 20 kW MHD20BM diesel generator use?

The Marsun MHD20BM has a specific consumption of less than 204 g/kWh, so at the full 20 kW it burns about 4.1 kg, or 4.9 l, of diesel per hour.

Does the MHD20BM have an ATS?

No, the Marsun MHD20BM has no built-in ATS: the ATS module is optional and bought separately. With a hybrid inverter you do not need an ATS, because the inverter’s signal starts the generator through the Two-Wire Switch port.

Which inverters is the MHD20BM compatible with?

The manufacturer states that the Marsun MHD20BM is compatible with Deye, Solis, Solplanet, GoodWe, Victron Energy and Sungrow hybrid inverters. The generator connects to the inverter’s generator input.

Can I connect the generator straight to the house’s distribution board?

No. The MHD20BM may be connected to a house’s wiring only through a fixed connection with measures that stop voltage from reaching ESO’s grid, and only by qualified specialists. Hybrid Energy handles this: we deliver anywhere in Lithuania, install and connect it.

Is the MHD20BM suitable for a house, farm or building site?

Yes. The 20 kW Marsun MHD20BM is intended for backup power for homes and farms, building sites, solar systems with storage and off-grid systems. Hybrid Energy helps you work out whether this output is enough for your site.

How loud is the MHD20BM?

The manufacturer states a noise level of 72 dB for the Marsun MHD20BM. Near homes, consider the neighbours when choosing where to put the generator.

Can I connect single-phase appliances to the MHD20BM?

Yes, the MHD20BM also supplies single-phase 230 V, but you will not get the full 20 kW on one phase. Single-phase loads must be spread evenly across the three phases.

How does the MHD20BM differ from the MHD20B?

The Marsun MHD20BM is the same 20 kW generator as the MHD20B, with the 490D engine and 60 l tank, but it also has remote parameter monitoring over Modbus. Neither has a built-in ATS; the MHD20 model does.

How does the MHD20BM differ from the MHD20?

The Marsun MHD20BM has a 60 l tank, a 490D engine (2554 cm³) and weighs 720 kg, while the MHD20 has built-in ATS, a 70 l tank, a YCV2.5N35-G20 engine (2500 cm³), weighs 650 kg and has an additional fuel pump. Both have Modbus.

Sources

• Marsun MHD20BM manufacturer datasheet (PDF), checked 2026-10-26
• ESO, Recommendations for setting up a backup source (in Lithuanian), checked 2026-10-26