Buying a diesel generator requires a responsible approach, because it is expensive equipment that is purchased for more than one year. Moreover, the functioning of instruments and equipment of the whole building or construction site will depend on it. Making the wrong choice will be unforgivable if the power supply is interrupted or serious damage occurs. At a commercial or manufacturing enterprise, this can lead to downtime, loss and damage to the goods, and in everyday life it will cause a lot of inconvenience. After all, the reason for buying an autonomous station is the need for a reliable source of electricity, which will not fail under any circumstances. To a greater extent, the efficiency of the station depends on the right choice according to technical characteristics.
How to calculate the power?
Whether the generator will be used to power all the equipment in the house or only a few units, it is important to correctly determine the load. If you take equipment of less power than the total power of all connected devices, then overload cannot be avoided. This may cause the generator to malfunction. But buying a station with too much power is also not recommended, because from prolonged idling the engine undergoes no less wear. To select the optimal power station, you need to make simple calculations. We will write the calculation algorithm in 5 steps.
Step 1: We determine the number of appliances who will be connected to the power plant at the same time. You also need to find out the power consumption of each of them. You will find information about this in the instructions or technical data sheet of the equipment.
For example, you intend to use a diesel power plant to power the following appliances:
- 6 incandescent lamps (60 W each),
- refrigerator (200 W),
- microwave (1500 W),
- electric kettle (1000 W),
- computer (500 W),
- TV (100 watts).
Do not rush to add these indicators, because you need to remember one more important thing. When connecting appliances to the generator with electric motors, such as a refrigerator, vacuum cleaner or power tool, it should be noted that during startup the load on the network increases several times.
Step 2: We take into account the coefficients of inrush currents to compensate for the increasing power during the start-up of equipment and machinery with electric motors. Depending on the magnitude of the starting currents, the equipment will have a certain coefficient. You will find examples in the table.
| Name of equipment | Power, (W) | Inrush Current Ratio |
| Toaster, coffee maker | 600 – 1500 | 1 |
| Hairdryer, Iron | 500 – 2000 | 1 |
| Electric stove | 1000 – 6000 | 1 |
| Heater | 1000 – 2400 | 1 |
| TV | 100 – 400 | 1 |
| Electric kettle | 1000 – 2000 | 1 |
| A computer | 400 – 750 | 2 |
| Refrigerator | 150 – 600 | 3 |
| Microwave | 1500 – 2000 | 2 |
| Fluorescent lamps | 3 – 36 | 2 |
| Incandescent lamps | 60 – 100 | 1 |
| Drill | 400 – 1000 | 3 |
| Hammer drill | 600 – 1400 | 3 |
| Compressor | 750 – 2500 | 4 |
| Submersible pump | 500 – 1000 | 7 |
It turns out that in our case it is necessary to lay the refrigerator power at 600 W (200 * 3), microwave power at 3000 W (1500 * 2) and computer power at 1000 W (500 * 2).
Step 3: Add up the power values of all appliances to get their total electricity demand.
60 * 6 + 600 + 3000 + 1000 + 1000 + 100 = 6060 (W)
Step 4: Add a power margin of 10% as a reserve . This is necessary in order not to use the entire engine life and reduce its wear.
6060 * 1.1 = 6666 (W)
It turns out that for efficient energy supply of the listed units of equipment, a diesel generator with a capacity of at least 6.6 kW is needed.
Step 5: Choose a model of the generator that is suitable for the power parameter. It is clear that it is not always possible to find a generator with exactly the same power value that you got when calculating. It’s not scary if the power of the station is 6.8 or 7 kW.
It’s important to know! When choosing a diesel generator, you can see two power values: maximum and nominal (for example, 6.48 and 5.85 kW). You need to focus on the second indicator, since it is recommended for the continuous operation of the equipment. It is possible to use maximum power only for a short time, so as not to overload the engine.
When making calculations, you should not summarize the power of all electrical appliances that you have at home or in the company. After all, they are not always used. For example, a hair dryer, an iron and a vacuum cleaner are almost never used at the same time, so you can take the average power value of these appliances and take it into account once. This is beneficial not only from the point of view of purchasing equipment (you do not have to overpay for installing more power), but also from the point of view of operation – the engine will not work for nothing.
Use the above calculation algorithm when choosing a diesel generator, and you will definitely not be mistaken. Today, the market for power plants has devices in a wide power range: from 1 kW to several thousand kilowatts. Therefore, it is easy to choose a suitable source of electricity based on the needs of a particular object that needs to be supplied with electricity: a summer house, a private house, a workshop, a construction site or an entire business.
Determine the voltage value
Here the choice should be based on what kind of power appliances you plan to connect to the diesel generator. Household appliances operate from a network with a voltage of 220 V, and powerful industrial equipment, such as machines and compressors, can be connected to a power source that produces a voltage of 380 V. If the specifics of your activity are connected with the use of those and other consumers, the best option would be a diesel station with two outputs: 220 and 380 V.
It’s important to know! You may have heard about such a thing as “phase imbalance”. It occurs when a consumer is connected to one of the phases, the power of which exceeds 1/3 of the total generator power. As a result, sudden voltage drops occur. To avoid this, connect consumers in such a way that their power consumption in each phase is approximately the same.
All attention to the volume of the fuel tank
Everyone knows that the duration of the generator’s operation without refueling directly depends on the tank’s volume. The more fuel you can pour in, the longer the duty cycle. But you should not buy a generator with a large tank, if this is not required by the operating conditions. For example, you will work with the unit for no more than 4 hours a day, and you will have a fuel reserve of 16 hours. This is irrational not only in terms of diesel fuel costs, but also the purchase of the station. After all, a large tank increases the size of the station and increases its price. To make the right choice, count how often and for how long an autonomous power source will be used.
For example, when using a diesel generator as a backup source of electricity for several hours, before the resumption of the central electricity network, a fuel reserve of 10 – 12 liters will be sufficient. For long-term operation of the station, a more capacious tank is needed. For example, a stock of 84 liters of fuel is enough for 8.5 hours of operation (with a consumption of 9.8 l / h). This is an excellent option for supplying electricity to tools and equipment in the workplace during the shift. To ensure round-the-clock operation of the power plant, it is possible to organize a fuel supply system from a separate tank, but this option is provided only for some models of stationary installations.
Do not forget about the dimensions
Diesel generators like no other are presented in a variety of designs by type of design, overall dimensions and weight. You can find both a portable model, which fits in the trunk of a car, and a large-sized, powerful installation designed for stationary placement. In this case, it all depends on the power: the more powerful the engine, the larger it is, therefore, the size of the entire generator structure (the volume of the oil and fuel tank, the dimensions of the fuel system and other parts) also increases.
For field work or for using the generator in the country, a portable model of a frame type is suitable . As a rule, the length of the unit does not exceed 1 meter, and it weighs no more than 100 kg, so one physically strong person can transfer it to the right place. Larger models, weighing over 100 kg, have wheels for easy transportation, for example, on a construction site. If you buy a diesel power plant for permanent use at home or at the enterprise and are not going to move it often, you can choose a stationary model. Such equipment weighs more than 1000 kg, and the length of the case can be several meters.
Now you know that there is nothing complicated in choosing a diesel generator. The main thing is to accurately formulate your requirements and make simple calculations. Having decided on the main operating parameters, you can easily choose the equipment that will best meet your needs.
