How to Select a Suitable Generator Set According to the Load?

Diesel generator set is a common emergency power supply in civil buildings, the proper selection of diesel generator set is an important problem in the electrical design of civil buildings. So when we choose self-contained diesel generator set, how to select a suitable capacity according to the load?

1.Setting principle.

Class I high-rise buildings shall be supplied power according to class I load requirements. Class II high-rise buildings shall be supplied power according to class II load requirements. 

Article 3.1 of code for electrical design of civil buildings (JGJ / t16-92): The primary load shall be supplied by two power sources, when one power supply fails, the other power supply should not be damaged at the same time; When the secondary load conditions permit, two-way power supply should also be used for power supply, especially the secondary load for fire protection, the power supply shall meet the requirements of two return circuits. For the particularly important load in the primary load, in addition to the above two power supplies, emergency power supply must be equipped. 

According to these regulations, Starlight manufacturer summarizes the setting principles of the self-contained diesel generator set:

A.When the power supply of civil buildings is required to meet the requirements of class I load, ff the city power grid can provide two independent power sources (one for use and one for standby or mutual standby), we do not need to equip with diesel generator set. However, when there is a particularly important load in the primary load, the diesel generator set shall be generally set as the emergency power supply.

B.When the grid can only provide one way of power supply, in order to meet the power supply requirements for the primary and secondary loads, diesel generator sets shall be set generally. At this time, the diesel generator set will be used as standby power supply and emergency power supply. In large and medium-sized commercial buildings, in order to ensure that the interruption of power supply will not cause great economic losses, it is also advisable to set up diesel generator set. Because the city power grid cannot be completely independent, sometimes when one power supply sources fails or is overhauled, another power supply sources may fail at the same time. Therefore, in order to ensure the reliable power supply of fire fighting and other important equipment (such as intelligent equipment, communication equipment, etc.) in civil buildings, diesel generator sets are generally set, even if there are two or more power supplies.

2.Selection of diesel generator set capacity.

For selection of self-contained diesel generator set capacity, there is not a unified calculation formula. Some are simply determined by 10% - 20% of the capacity of power transformer. Some count by the total capacity of fire fighting equipment. If the capacity selection is too large, it maybe cause a waste of investment, the capacity is too small, it maybe not meet the use requirements in the event of an accident. So, how to choose the capacity of self-contained generator set?

A.Scheme or preliminary design stage.

The capacity of the self-contained generator set is calculated as 10% - 20% of the total capacity of the power supply transformer.

B.Construction drawing stage.

The power load of buildings can be divided into three categories:

The first type is security load. It means the load to ensure the safe and reliable operation of people and equipment in the building. Such as fire pump, fire elevator, smoke control equipment, emergency lighting, communication equipment, important computer and related equipment, etc;

The second type is the guaranteed load, that is, the basic equipment load to ensure the operation of the building, mainly including the working area lighting, part of the elevator and the passage lighting;

The third type is general load, i.e. other loads besides the above loads, such as air conditioning, water pump and other general lighting and power equipment.

When the buildings must be equipped with diesel generator, the first type of load shall be taken into account.

The second type of load is determined according to the function of the building and the situation of the power grid. If the functional requirements of the building are high or the power supply of the city power grid is unstable, the second type of load shall be taken into account. However, if the first and second types of loads are simply added to select the diesel generator capacity, the selected capacity is too large. Because in the state of fire protection, only the operation of fire-fighting equipment shall be ensured, and the second type of load has not be used. While the power grid is cut off in non fire-fighting state, the fire-fighting equipment will not be used. We can select the larger one of the two capacities as the capacity of diesel generator set.

We should select different diesel generator set capacity according to different requirements. If you do not know how to select, you can ask engineer or electrician to count for you.

Of course, if you have plan to purchase diesel generator set, you can also contact us. We will recommend the most suitable generator set for you. Starlight has a wide capacity of genset from 25kva to 3125kva with varied brands( Cummins, Perkins, Volvo, Deutz, Yuchai, Shangchai, Wuxi, Ricardo etc.). We believe there will always be one you want.