Matters needing attention when purchasing diesel generator sets

Matters needing attention when purchasing diesel generator sets

We are a Chinese manufacturer-PowerSUM.

Buyers who do not understand diesel generator sets will have a hard time making a choice.

We will give you a general introduction to the things you need to pay attention to when purchasing.


With the popularity of the industry, the demand for electricity is increasing, and the diesel generator sets have also become popular. So how do users buy diesel generator sets?


  1. Eight traps that users should pay attention to when purchasing


1 Confuse the relationship between KVA and KW. Treat KVA as KW to exaggerate power and sell it to customers. In fact, KVA is apparent power, KW is effective power, and the relationship between them is IKVA=0.8KW. Imported units are generally expressed in KVA, while domestic electrical equipment is generally expressed in KW, so when calculating power, KVA should be converted into KW at a 20% discount.

  1. Don’t talk about the relationship between long-running (rated) power and backup power, just say one “power”, and sell the back-up power as long-running power to customers. In fact, backup power = 1.1x long line power. Also, the backup power can only be used for 1 hour out of 12 hours of continuous operation.
  2. The power of the diesel engine is configured as large as the power of the generator, in order to reduce the cost. In fact, the industry generally stipulates that the power of the diesel engine is greater than or equal to 10% of the power of the generator, because of mechanical losses. Even worse, some misreport the horsepower of the diesel engine as kilowatts to the user, and configure the unit with a diesel engine less than the power of the generator, commonly known as: small horse-drawn cart, so that the life of the unit is reduced, maintenance is frequent, and the usage fee is high. Not too high.
  3. The refurbished second-hand mobile phone is sold to customers as a brand-new machine, and some refurbished diesel engines are equipped with a new generator and control cabinet, so that ordinary non-professional users cannot tell whether it is a new machine or an old machine.
  4. Only report the brand of diesel engine or generator, not the place of origin and the brand of the unit. Such as Cummins in the United States, Volvo in Sweden, and Stanford in the United Kingdom. In fact, it is impossible for any diesel generator set to be completed by an enterprise independently. Customers should have a comprehensive understanding of the diesel engine, generator, and control cabinet manufacturers and brands of the unit in order to comprehensively evaluate the grade of the unit.
  5. The unit without protection function (commonly known as four protections) is sold to the customer as a unit with complete protection function. What’s more, the unit with incomplete instrumentation and no air switch is sold to customers. In fact, it is generally stipulated in the industry that units above 10KW must be equipped with full instruments (commonly known as five meters) and air switches; large units and automated units must have self-four protection functions.
  6. Not to mention the brand grade of diesel engine and generator, the configuration of control system, not to talk about after-sales service, but only to talk about price and delivery time. Some also use non-power station-specific oil engines, such as marine diesel engines and vehicle diesel engines for generator sets. The quality of electricity (voltage and frequency), the final product of the unit, cannot be guaranteed. Units with too low prices generally have problems, commonly known as: only the wrong purchase is not the wrong sale!
  7. Don’t talk about random accessories, such as with or without muffler, fuel tank, fuel pipe, what grade of battery, how much capacity battery, how many batteries and so on. In fact, these attachments are so important that they must be stated in the contract. What’s more, they don’t even bring the fan of the water tank, so that the customer can open the pool by himself.

Diesel generator set is an important backup power supply equipment, and it is necessary to be cautious when purchasing it, and it can only be handy when using it.


  1. Unit purchase

When purchasing a diesel generator set, the comprehensive performance and economic indicators of the diesel generator set should be fully considered, the professionalism, geographical location and actual professional level of the supplier, and whether the supplier has after-sales service means, such as emergency repair vehicles, special equipment, etc. Then consider whether the power of the selected unit matches the power of the electrical load. Generally, it is better to select the power of the unit by: the rated power of the unit x0.8 = the power of the electrical equipment. If there are large and medium-sized motors, 2-5 times the starting current needs to be considered. If the unit is mainly used to charge the UPS, a professional consultation must be made according to the actual situation of the UPS, and then the rated power of the generator is determined.

  1. Unit installation

Before the diesel generator set is used, it should be installed and connected. When installing diesel generator sets, pay attention to the following matters:

  1. The installation site should be well ventilated. There should be enough air inlets at the generator end and good air outlets at the diesel engine end. The area of ​​the air outlet should be more than 1.5 times larger than the area of ​​the water tank.
  2. The surroundings of the installation site should be kept clean, and items that can generate acid, alkali and other corrosive gases and vapors should be avoided. Where possible, fire extinguishing devices should be provided.
  3. If it is used indoors, the exhaust pipe must be led to the outside, and the diameter of the pipe must be greater than or equal to the diameter of the exhaust pipe of the muffler. The pipe is inclined downward by 5–10 degrees to avoid rainwater injection; if the exhaust pipe is installed vertically upward, a rain cover must be installed.
  4. When the foundation is made of concrete, the horizontality must be measured with a level ruler during installation, so that the unit can be fixed on a horizontal foundation. There should be special shock-proof pads or foot bolts between the unit and the foundation.
  5. The casing of the unit must have a reliable protective grounding. For generators that need to have a neutral point directly grounded, the neutral point must be grounded by professionals and equipped with lightning protection devices. It is strictly forbidden to use the grounding device of the mains for neutrality point directly to ground.
  6. The two-way switch between the generator and the mains must be very reliable to prevent reverse power transmission. The wiring reliability of the two-way switch needs to be checked and approved by the local power supply department.
  7. The wiring of the starting battery must be firm.


  1. Unit supporting

In addition to the accessories provided by the supplier, there are some optional accessories for diesel generators, such as fuel tanks, mains chargers, fuel oil pipes, etc. Knowing how to purchase these add-ons is essential. First of all, the fuel storage capacity of the unit’s fuel tank should be able to provide the unit with full-load continuous operation for more than 8 hours, and try to avoid refueling in the fuel tank when the unit is running. Secondly, the mains charger should use a special charger with floating charge to ensure that the battery can drive the unit to run at any time. Use anti-rust, anti-freezing and anti-boiling liquid as coolant as possible. It is necessary to use the special oil for diesel engine above CD grade.

Five, the importance of the mains switch

The mains switch is divided into two types: manual and automatic (referred to as ATS). If your diesel generator is used as a backup power supply, you must install a mains switch at the input point of the power supply. It is strictly forbidden to input self-supplied power to the load by means of temporary wiring and memory operation. Because once the self-provided power supply is connected to the grid without authorization (referred to as reverse power transmission), it will cause serious consequences of casualties and equipment damage. Whether the installation of the switch is correct or not, it must be checked and approved by the local power supply department before it can be put into use.