What You Need to Know About Emergency Diesel Generator Sizing Calculation

Emergency diesel generators (EDGs) provide robust and dependable backup power supply in the event of a failure of the regular power supply. They are commonly used in hotels, hospitals, emergency services, health care facilities and similar institutions. These generators enable critical facilities to continue operating and minimize business and data losses during power outages. When buying an emergency diesel generator, how to calculate what size generator you need? Read on and you will find the answer.

Understanding the generating set ratings

Generator set ratings are operating values that manufacturers provide for users, telling them how much power an engine can produce under certain conditions. Generally, basic generator set rating categories are defined based on four operational categories: Emergency Standby Power (ESP), Prime Power (PRP), Limited-Time Running Prime (LTP) and Continuous Power (COP). The emergency standby rating is the most commonly applied rating and represents the maximum amount of power that a generator set is capable of delivering. Please note that an ESP-rated generator set does not have the ability of overload. The maximum power available for the duration of the grid interruption is the size rating of the generator. It may run for a maximum of 200 hours per year.

An emergency diesel generator can keep your business running smoothly when the power goes out, but only if you choose the right size and power capabilities.

The importance of proper generator sizing

Buying a generator is a challenging task, because you need to consider many factors. What size generator is appropriate is a key consideration. If the generator you choose is too large, it may lead to the following problems:

Damage to generator itself

Damage to electrical systems

Unnecessary operational expenses

Lower oil performance, high oil consumption

Inefficient power production

Increased pollution

If the emergency generator is too small, the following problems may occur:

Generator damage or overheating

Damage the equipment connected to the generator

Insufficient or unreliable power

Critical facilities and security system failures due to load loss

Voltage and frequency output may become unstable

Therefore, it’s important to choose the right size generator for your business.

How do you size an emergency diesel generator?

Assess your power requirements

First of all, you need to determine all of the site loads that require an emergency diesel generator. Make a list of all items that need to be powered. This varies widely depending on what type of business you operate, which may include machinery, lighting, security, telecommunications, and any other systems that are essential for safety and operations.

Calculate the required wattage

Most electrical equipment have different starting and running wattages. Starting wattage is the initial energy surge required to turn it on. Running wattage is the power needed to operate it. Some items only have running wattage. Typically, these figures can be found on the equipment itself and in the owner’s manual. To calculate your total power requirement, add the running watts of all the items you wish to power at the same time, and then add the highest number of starting watts among the items.

If you can’t determine the running watts of an item which is rated in amperes, you can use the following formula to convert amps to watts:

For resistive loads (most common type): Wattage = amperes x volts

For reactive loads: Wattage = amperes x volts x load factor

When you know the amount of power you will need from an emergency diesel generator, it’s not difficult to choose the right generator size. Choose a generator with a capacity that’s 10-20% larger than your requirement.

Usually, generators are rated using kilowatts-volts-amperes (kVA), which measures the apparent power of the generator. Kilowatts (kW) measure the real electric power supplied by the generator. The power factor (PF) is the ratio between real power and apparent power, which measures the efficiency with which the generator uses its energy. The power factor is between 0 and 1, with the closer the number is to 1, the more efficient the system. Diesel Generators have a power factor of around 0.75-0.8. For example, if a 100kVA diesel generator has a power factor of 0.8, it supplies the load with a maximum output power of 100 x 0.8 = 80 kW.

Contact Dingbo Power to ensure you have the right generator

Emergency diesel generators should provide reliable backup power source in an emergency. If you’re unsure about the generator size or the type of generator that best fits your needs, feel free to contact us. Dingbo Power is a professional diesel generator manufacturer with more than 17 years’ production experience. We integrates the design, supply, commissioning and maintenance of diesel generators and offers products that can meet expectations in a variety of applications. Don’t hesitate to reach out for any further information or assistance regarding to generators. Contact us today!