Marsun MHD20B 20 kW Three-Phase Diesel Generator

The Marsun MHD20B 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. It differs from the MHD20BM only in having no remote monitoring over Modbus, and 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 an inverter controls the generator and Modbus is not needed: backup power for homes, farms and 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 MHD20B differs from the MHD20BM and MHD20

Choose the MHD20B if a hybrid inverter will start the generator and you do not need to monitor it remotely. If you want Modbus monitoring, take the MHD20BM: same output, engine and tank. 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 MHD20B use, and how long does it run on a full tank?

The manufacturer states that the MHD20B has a 60 l tank and runs continuously for up to 8 hours. Plan your backup power around this figure.

An indicative calculation from the specific consumption: 204 g/kWh × 20 kW is about 4.1 kg of diesel per hour, or roughly 4.9 l/h (diesel density 0.84 kg/l). By that formula the 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 does not provide an additional fuel tank or additional fuel pump for this model.

Diesel generator with ATS: how does automatic start work on the MHD20B?

The MHD20B has a factory dry-contact Two-Wire Switch connection. It is a simple two-wire link through which a hybrid inverter or an ATS module can start and stop the generator without anyone present.

• 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 low, the inverter sends a signal to the Two-Wire Switch connection, 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 grid, starts the generator when the voltage drops, switches the site supply over, and shuts the engine down and reconnects the grid when mains power returns.

Closing the contact starts the generator; opening it shuts the engine 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 done by a certified electrician.

How do I connect a backup generator to a house or site?

A generator may be connected to a site’s internal network only through a fixed connection, and switching 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

The same ESO guidance advises choosing the power according to your connection capacity and, when connecting single-phase loads to a three-phase generator, taking the single-phase limit into account, because the datasheet gives the total power of all three phases.

We handle it for you. We select the equipment for your site, deliver anywhere in Lithuania, install and connect it.

What to know before buying

• ATS: not built in. With a hybrid inverter you do not need one; for automatic grid-to-generator switching without an inverter, an ATS module must be bought separately. If you want ATS from day one, the MHD20 is the same-power version with built-in ATS.
• Noise: the manufacturer states 72 dB, so consider where you place it in relation to occupied buildings.
• Weight and transport: the generator weighs 720 kg and measures 2000 × 900 × 1200 mm. Unloading and moving it needs certified straps or lifting equipment of suitable capacity.
• Fuel: diesel, 60 l tank. This model has no additional fuel pump, additional tank or heated fuel unit.
• Monitoring: there is a frequency and voltage indicator, but no remote parameter monitoring via Modbus.
• 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).
• Protection: no-load operation protection, overcurrent breaker, overpressure protection, smart fuel saving.

Frequently asked questions

How many hours does the MHD20B run on a full tank?

According to the manufacturer, the Marsun MHD20B 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 a 20 kW diesel generator like the MHD20B use?

The specific consumption of the Marsun MHD20B is 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. At lower loads consumption is lower.

Does the MHD20B have ATS?

No, the Marsun MHD20B has no built-in ATS: an ATS module is optional and bought separately. With a hybrid inverter you do not need one, because the inverter’s signal starts the generator through the Two-Wire Switch connection.

Which inverters is the MHD20B compatible with?

The manufacturer states that the Marsun MHD20B 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 my house fuse board?

No. The MHD20B may be connected to the building’s network only through a fixed connection with measures that stop voltage reaching ESO’s grid, and only by qualified specialists. Hybrid Energy takes care of this: we deliver anywhere in Lithuania, install it and bring it into service.

Is the MHD20B suitable for a home, a farm or a building site?

Yes, the 20 kW Marsun MHD20B is intended for backup power at homes and farms, building sites, solar systems with batteries and off-grid systems. Hybrid Energy helps you work out whether this power is enough for your site.

How loud is the MHD20B?

The manufacturer states a noise level of 72 dB for the Marsun MHD20B. Near homes, choose the generator’s location with your neighbours in mind.

Can I connect single-phase appliances to the MHD20B?

Yes, the MHD20B also supplies 230 V single-phase power, but you will not get the full 20 kW from one phase. Single-phase loads must be spread evenly across the three phases.

What is the difference between the MHD20B and the MHD20?

Both are 20 kW three-phase diesel generators, but the MHD20B has no built-in ATS or Modbus, has a 490D engine (2554 cm³) and a 60 l tank, while the MHD20 has built-in ATS, Modbus and a 70 l tank.

What is the difference between the MHD20B and the MHD20BM?

The Marsun MHD20B and MHD20BM are the same 20 kW generator with a 490D engine and 60 l tank, but only the MHD20BM has remote parameter monitoring over Modbus. The MHD20B does not.

Sources

• Marsun MHD20B manufacturer datasheet (PDF), checked 2026-10-26
• ESO — Recommendations for installing a backup power source, checked 2026-10-26