How to choose a Generator

This is the first question to ask before you buy a generator:

a) If you have no supply of electricity from a grid source or Public Supply Company and you need it for your facility for 12 hours a day: We recommend a Prime Power generator. Note: If you have specific continuous base load or motor starting requirements contact us with full details.

b) If you have no supply of electricity from a grid source or Public Supply Company and you need a generator for your home for 12 hours a day: We recommend a Prime Power generator.

c) If you have a break in Electricity supply for up to six hours a day (Domestic or industrial premises): We recommend a Standby generator.

d) If you have a constant supply of electricity, but it is essential you have an emergency back up for maximum of 500 hours a year (approximately 1.5 hour a day): We recommend a Standby Generator or Maximum Power Generator (available only for few sizes, also limited to Maximum 500 hours use in a year).

e) If you are a Contractor and need electricity for your site for a maximum of 6 hours a day (maximum 2000 hours a year): We recommend a Standby power generator.

f) If you are a contractor and need electricity on site for up to 12 hours a day (maximum 3000 hours a year): We recommend a Prime Power generator.

g) If you need a generator for your leisure time (maximum 500 hours a year): We recommend a cheap petrol portable generator.

h) If your grid source or Public Supply Company electricity is unstable and you need a steady current for your computers or other sensitive equipment: We recommend portable generator with an automatic voltage regulator control system in the alternator. It may also be appropriate to have an engine equipped with electronic governing for close frequency (Hz) control.

The Generating Set size can be determined by the total demand of your powered equipment. Below you can find the typical energy
requirement for each electrical appliance in your house. This will help you to obtain a general idea of your total load. As stated we
strongly recommend that before you make your final decision to purchase you seek advice from a local Electrical Engineer or
Consultant who is best qualified to assist you in choosing the right size and may have equipment available to monitor your load
demand over a period of time to determine your maximum and minimum demand.

Remember: buying a Generator that provides lower capacity than needed - may damage both the engine and the alternator. It should
also be noted that engine driven generators need to be loaded to a minimum of 50% of rated output at all times in order to prevent
mechanical damage, even if this means running unnecessary appliances to make up the demand.

Please learn more about this subject in our FAQ "under load" and "over load".
Please see our separate estimating table for load calculation.

Choosing the Generator engine type is a sensative issue combining capital investment costs and operating costs.

The cheapest operating costs are for Gas fuelled generators. In sizes up to 100 KW Gas generators can be up to 30% more expensive than Diesel fuelled generators with the same output. If Gas is available and you are going to operate your generator for more then 2000 hours a year, this can be the most cost effective solution Gas is also much more environment friendly.

Choosing the Generator engine type is a sensative issue combining capital investment costs and operating costs.

The cheapest operating costs are for Gas fuelled generators. In sizes up to 100 KW Gas generators can be up to 30% more expensive than Diesel fuelled generators with the same output. If Gas is available and you are going to operate your generator for more then 2000 hours a year, this can be the most cost effective solution Gas is also much more environment friendly.

Kerosene engines are not expensive to buy and have comparatively low running costs. They are limited in output generally not exceeding 5KVA.An additional advantage in using Kerosene fuel is that it is less volatile and thus much safer than Petrol.

Petrol Engines are the cheapest to purchase and the most expensive to operate. If you need a Generator to operate for up to three hours a day, they are a good choice.

In general, Petrol fuelled generators are limited to maximum output of 20KVA and minimum speed of 3000 RPM.

Diesel Generators are commonly available with outputs from 5 KVA up to 2500 KVA. They are significantly cheaper to operate and maintain compared to Petrol, but more expensive then Petrol engines. If you need a generator for more then 3 hours a day, or a minimum of 1500 hours annually, we recommend that you to buy a Diesel Generator.

If you are going to use your generator in one place and have access to mains supply (residential, factory or business office), and you have the funds - buy a Generator with automatic start and an automatic change over system. Automatic Mains Failure systems are reliable and they are competitively priced.

If you use your set for a construction site or temporary placement, use a manual start generator.

In many cases, by law you must use automatic AMF systems.(hospitals, clinics, banks, cold rooms, etc).

All well known engine brands are good and reliable. The main question when choosing a brand of engine is: Can I obtain local service and spares support and is the initial capital cost competitive.

First check local service support, then the cost - a Generator without good local back up service is not a cost effective solution.

The most popular alternators in the market are: Newage Stamford, Meccalte, Leroy Somer and Marathon. All of these brands are very reliable and are built for long term operation.

The key questions here yet again are, is the prime cost competitive and what is the availability of product support locally. The main exchange parts that you may need for Alternators are automatic voltage regulators and diodes. These items are available in most countries for all of the above brands.

Engines in generating set packages operate in two fixed speed bands: Low speed: 1500rpm for 50Hz or 1800rpm for 60Hz High speed: 3000rpm for 50Hz or 3600rpm for 60Hz.

High speed engines are cheaper to buy but their life span is significantly shorter. They are also limited to providing a maximum generator electrical output of 35kva. They are acceptable for Stand By use of up to 2000 hours in a year or when finances are limited.

Low speed engines are more expensive, but have greater longeivity. They are the better choice when operational requirements are above 1000 hours annually.

Single phase Generators are generally limited to 25KVA output as it is generally cheaper to take single phase supply from the phases of a 3 phase machine than buy a dedicated unit for outputs above this level. Choosing a single phase or three phase output is strictly determined by the purpose of the set. Note that a single phase machine is dedicated to monophase output, whereas it is possible to take both single and three phase supply from a three phase Generator.

If all of your appliances are one phase and you are going to use it for your house or working site, then the single phase Generator is the set to chose. If you have any three phase appliances you will need a three phase set.

An open generator comprises an engine and alternator assembled to a steel skid baseplate with an electrical control panel.

Soundproof generators are installed in a canopy that reduces the noise of the equipment and also protects it from the weather. The canopy also offers a degree of security.

Soundproof canopies are categorized by the amount of noise reduction they provide (DBA). The greater the level of noise reduction - the higher the cost of the Generator package

How to choose between the two? There are two major factors to consider: a. In some locations you must use silent generators by law. b. Personal preference to limit noise for your convenience or your neighbours.

So, where can you use open generators? Open generators are used in generator rooms or in remote areas, where you are not limited by the noise and a shed is enough to protect your set.

These ratings are defined by international standards.

Base load ratings are for generator operation continuously, without breaks other than for fuelling and maintenance. They are usually capable of sustaining a 10% overl0ad output for 1 hour in every 12 hours of operation.

Prime power ratings are 10% above base load outputs and relate to generators operating under continuous conditions but with consistently variable loads. . They are usually capable of sustaining a 10% overl0ad output for 1 hour in every 12 hours of operation.

Standby power ratings offer 10% more output than prime power subject to variable load and limited to a fixed running period annually which is determined by the Engine Manufacturer. These operating periods vary considerably between different brands of engine. No overload is allowed.

The KVA, KW rating of generators is based on engine and alternator outputs at Normal Temperatures and Pressures (N.T.P.) generally defined as 25ֳ· Centigrade at sea level. If the Generator is required to operate in high temperatures, at high altitude or in a combination of these conditions, a derate in output performance may occur.

If you have no mains electricity at all you need a base load generator. This is a generator that can run from one service to the other non-stop. You can use a prime power rated Generator at up to 90% of its capacity.

If you live in a place where the public supply of electricity is not reliable and you need back for up to 12 hours a day buy a generator with a prime power rating.

If you need a Generator on standby for not more than 500 hours a year, or you need to provide a generator as a back up by law use a standby rated machine Some Manufacturers have special lines of Generators for these purposes but they are very strict about using these sets for No More then 500 hours a year.

Check the Manufactures recommendations. You might lose your guarantee and warranty for the engine if you use a prime power rated engine in a base load application.