The complete guide to diesel generators: components & use

by Joost Nusselder | Updated on:  September 2, 2020
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A diesel generator is made of the diesel engine and electric generator to produce electrical energy.

It is specifically designed to use diesel, but some types of generators use other fuels, gas, or both (bi-fuel operation). As you’ll see, we will discuss 3 types of generators, but focusing on diesel.

In most cases, diesel generators are used in places that are not connected to the power grid and sometimes as power back-up in case of outages.

Also, generators are used in schools, hospitals, commercial buildings, and even mining operations where they provide the power necessary for the operation of heavy-duty equipment.


The combination of the engine, electric generator, and other components of the generator is referred to as the generating set or gen set.

Diesel generators exist in different sizes depending on the usage. For instance, for small applications such as homes and offices, they range from 8kW to 30Kw.

In the case of large applications such as factories, the size varies from 80kW to 2000Kw.

What is a diesel generator?

On the most basic level, a diesel generator is a diesel Genset which is made from a combination of a diesel-fueled engine and an electric generator or alternator.

This critical piece of equipment creates electricity to power anything during a blackout or in places where there is no electricity.

Why is diesel used in generators?

Diesel is still a fairly cost-efficient fuel source. In general, diesel is priced a bit higher than gasoline, however, it has an advantage over other fuel sources.

It has a higher energy density, which means that more energy can be extracted from diesel than gasoline.

In cars and other automobiles, this translates to higher mileage. So, with a full tank of diesel fuel, you can drive longer than with the same volume of gasoline.

In short, diesel is more cost-effective and has an overall higher efficiency.

How does a diesel generator create electricity?

The diesel generator converts mechanical energy into electrical power. It is important to note that the generator does not create electrical energy but instead acts as a channel of electrical charges.

It works similarly to the water pump that only allows water to pass through.

First of all, air is taken and blown into the generator until it becomes compressed. Then, diesel fuel is injected.

This combination of air and fuel injection causes heat which subsequently causes the fuel to light up. This is the basic concept of a diesel generator.

To sum up, the generator works via the combustion of diesel.

What are the components of a diesel generator and how do they work?

Let’s examine all the components of the diesel generator and what their role is.

i. The engine

The engine part of the generator is similar to the vehicle engine and acts as the source of mechanical energy. The maximum power output a generator can produce is directly related to the size of the engine.

ii. The alternator

This is the component of the diesel generator that converts mechanical energy into electrical energy. The working principle of the alternator is similar to the process described by Michael Faraday in the nineteenth century.

The principle holds that an electric current is induced in an electrical conductor when passed through a magnetic field. This process causes electrons to flow through the electrical conductor.

The amount of the current produced is directly proportional to the strength of the magnetic fields. There are two main components of the alternator. They work together to cause the movements between the conductors and magnetic fields to produce electrical energy;

(a) Stator

It contains coils of electrical conductor wounded on an iron core.

(b) Rotor

It produces magnetic fields around the stator inducing voltage difference that generates alternating current (A/C).

There several factors that you should consider while determining the alternator, including:

(a) Housing

The metal casing is more durable than the plastic casing.

Besides, plastic casing gets deformed and may expose the components to increasing wear and tear and risk to the user.

(b) Bearings

Ball bearings last longer than needle bearings.

(c) Brushes

Brushless designs produce clean energy and are easier to maintain than those that contain brushes.

iii. The fuel system

The fuel tank should be sufficient enough to hold fuel for between six to eight hours of operation.

For small or portable units, the tank is part of the generator and externally erected for large generators. However, the installation of external tanks requires necessary approvals. The fuel system contains the following components;

(a) Supply pipe

This is the pipe that connects the fuel tank to the engine.

(b) Ventilation pipe

The ventilation pipe prevents pressure and vacuum from building up when refilling or draining the tank.

(c) Overflow pipe

This pipe prevents spillage of the fuel on the generator set when you refill it.

(d) Pump

It transfers the fuel from the storage tank to an operational tank.

(e) Fuel filter

The filter separates the fuel from water and other materials that cause corrosion or contamination.

(f) Injector

Sprays fuel to the cylinder where combustion takes place.

iv. Voltage regulator

The voltage regulator is an essential component of the generator. This component controls the output voltage. In fact, the regulation of voltage is a complicated cyclical process that ensures the output voltage is equivalent to the operating capacity.

Nowadays, most electrical devices rely on a steady power supply. Without the regulator, the electrical energy will not be stable due to the varying engine speed, therefore the generator doesn’t work properly.

v. The cooling and exhaust system

(a) Cooling system

Apart from the mechanical energy, the generator also produces a lot of heat. Cooling and ventilation systems are used to withdraw the excessive heat.

There are different types of coolants used for diesel generators depending on the application. For instance, water is sometimes used for small generators or huge generators that exceed 2250kW.

However, hydrogen is commonly used in most generators since it absorbs heat more efficiently than other coolants. Standard radiators and fans are sometimes used as cooling systems especially in residential applications.

In addition, it is advisable to place the generator in a sufficiently ventilated area to ensure an adequate supply of cooling air.

(b) Exhaust system

Similar to the vehicle engine, the diesel generator emits harmful chemicals such as carbon monoxide that should be managed efficiently. The exhaust system ensures that the toxic gases produced are appropriately disposed of to make sure people are not harmed by toxic exhaust fumes.

In most cases, the exhaust pipes are made of steel, cast, and wrought iron. They are not attached to the engine to minimize vibrations.

vi. Lubricating system

The generator includes moving parts that require lubrication for smooth operation and durability. The oil pump and reservoir attached to the engine automatically apply the oil. It is recommended you check the level of the oil every eight hours of operations to ensure the there is enough oil. At this time, make sure to check for any leakages.

vii. The battery charger

The diesel generator relies on a battery to start running. Stainless steel chargers ensure the battery is adequately charged with float voltage from the generator. The mechanism is fully automated and does not require manual adjustments. You should not tamper with this part of the equipment.

viii. The control panel

This is the user interface where the generator is controlled and operated. The features of each control panel vary depending on the manufacturer. Some of the standard features include;

(a) On/off button

The start button can either be manual, automatic or both. An auto-start control automatically starts the running of the generator when there is an outage. As well, it shuts down operations when the generator is not in use.

(b) Engine gauges

Display various parameters such as the temperature of the coolant, rotation speed, etc.

(c) Generator gauges

Shows the measurement of the current, voltage, and operating frequency. This information is essential because voltage issues can damage the generator and that means you won’t get a constant flow of power.

ix. Assembly frame

All generators contain a waterproof casing that keeps all the components together and provides safety and structural support. To conclude, the diesel generator converts mechanical energy into electrical power. This works through the electromagnetic induction rule, thus supplying energy when needed.

How many types of diesel generators are there?

There are 3 types of diesel generators you can purchase.

1. Portable

This type of moveable generator can be taken on the road with you to anywhere it is needed. Here are the general characteristics of portable generators:

  • to conduct electricity, this type of generator uses a combustion engine
  • it can be plugged into a socket to power tools or electrical appliances
  • you can wire it into facility subpanels
  • best for use in remote sites
  • it doesn’t create a lot of power, but it generates enough to run appliances such a TV or refrigerator
  • great for powering small tools and lights
  • you can use a governor which controls the engine speed
  • usually runs somewhere around 3600 rpm

2. Inverter Generator

This type of generator produces AC power. The engine is connected to an alternator and produces this type of AC power. Then it uses a rectifier that converts the AC power into DC power. Here are the characteristics of such a generator:

  • the inverter generator uses high-tech magnets to function
  • it is built using advanced electronic circuitry
  • when producing electricity it undergoes a three-step process
  • it provides appliances with a constant flow of electrical current
  • this generator is more energy efficient because the engine speed is self-adjusting depending on the amount of power required
  • the AC can be set to a voltage or frequency of your choice
  • these generators are lightweight and compact which means they easily fit into your vehicle

In summary, the inverter generator creates AC power, converts it to DC power, and then inverts it back to AC again.

3. Standby Generator

The role of this generator is to supply energy during a blackout or power outage. This electrical system has an automatic power switch which commands it to turn on in order to power up a device during an electrical outage. Usually, hospitals have backup generators to ensure the equipment keeps operating smoothly during a blackout. Here are the characteristics of a standby generator:

  • this type of generator operates automatically without the need for manual switching to on or off
  • it offers a permanent source of power as a protection from an outage
  • made of two components: first, there is the standby generator which is controlled by the second component called the automatic transfer switch
  • can operate on gas – natural gas or liquid propane
  • uses an internal combustion engine
  • it will sense power loss in a matter of seconds and starts running by itself
  • commonly used in the safety system of things like elevators, hospitals, and fire protection systems

How much diesel does a generator use per hour?

How much fuel the generator uses depends on the size of the generator, calculated in KW. As well, it depends on the load of the device. Here is some sample use per hour data.

  • Small Generator Size 60KW uses 4.8 gallons/hr at 100% load
  • Mid-sized Generator Size 230KW uses 16.6 gallons/hr at 100% load
  • Generator Size 300KW uses 21.5 gallons/hr at 100% load
  • Large Generator Size 750KW uses 53.4gallons/hr at 100% load

How long can a diesel generator run continuously?

While there is no exact number, most diesel generators have a running lifespan of anywhere between 10,000 to 30,000 hours, depending on the brand and size.

As for continuous functionality, it depends on your standby generator. Most generator manufacturers recommend that you run your generator for approximately 500 hours at a time (continuously).

This translates to about three or so weeks of nonstop use, which most importantly means that you can be in a remote area without worry for almost a month.

Generator Maintenance

Now that you know how a generator works, you need to know some basic maintenance tips for a diesel generator.

First, you need to follow the manufacturer’s recommended maintenance schedule.

Make sure to take the generator for an inspection once in a while. This means that they check for any leaks, check the oil and coolant level, and look at the belts and hoses for wear and tear.

Additionally, they usually check the generator’s battery terminals and cables because these break down in time.

Likewise, your generator requires regular oil changes to ensure optimal functionality as well as maximum efficiency.

For instance, a poorly maintained generator is less efficient and consumes more fuel, which in turn costs you more money.

Your basic diesel generator requires an oil change after about 100 operating hours.

What is the advantage of a diesel generator?

As discussed above, maintenance of a diesel generator is cheaper than a gas one. Likewise, these generators require less maintenance and repairs.

The main reason is that a diesel generator does not have spark plugs and carburetors. Therefore, you don’t need to replace those expensive components.

This generator is advantageous because it is the most reliable backup power source. Therefore, it is essential for hospitals for example.

The generators are easy to maintain in comparison to gas ones. Similarly, they offer a nonstop and uninterrupted power supply when the power supply fails.

In conclusion, we highly recommend that you get a diesel generator. It is a must-have if you go to areas without electrical power or you experience frequent outages.

These devices are extremely useful to power your appliances. As well, they are efficient and cost-effective.

Also read: these tool belts are great for amateur electricians as well as professionals

I'm Joost Nusselder, the founder of Tools Doctor, content marketer, and dad. I love trying out new equipment, and together with my team I've been creating in-depth blog articles since 2016 to help loyal readers with tools & crafting tips.