CAUTION

The power of a generator is expressed either in kVA or in kW.

As a rule of thumb, 1 kVA = ± 0.8 kW

HOW TO CHOOSE A GENERATOR

Begin by assessing your needs, answering the questions below as precisely as possible.

Then send all the information you have, together with any comments, proposals or questions, to your technical department as a basis for discussion.

Needs assessment

• What are the voltage and frequency of the mains supply in the country (110, 127 or 230 V; 50 or 60 Hz)?
• What are the needs of the appliances to be powered (single-phase or three-phase, power, tolerance etc.)? You are recommended to produce a diagram of the intended installation.
• What is the total power required, in kVA, including starting power?
• Is the generator intended for mobile or fixed use?
• What is the estimated duration of use: is it for emergency or long-term use? How many hours a day?
• What kind of fuel (petrol or diesel) is available locally and at what price?
• Which generators are available locally (brand, price, delivery lead time, spare parts etc.)?
• Is noise a problem? Should the generator be open, enclosed or soundproof?
• Where will the exhaust gases go? Will you need an exhaust pipe extension?

TECHNICAL SPECIFICATIONS

Engine

• Fuel: petrol or diesel. A diesel engine is heavier and more expensive, but is also more robust and recommended for long-term use (more than 1000 hours).
• Number of cylinders
• Capacity in cc
• Power, in HP or kW
• Engine speed: 1500 or 3000 rpm (the lifespan of a 1500 rpm generator is 3 times the lifespan of a 3000 rpm one)
• Fuel consumption per hour at full load
• Fuel tank capacity/operating time
• Cooling system: air, oil, or water
• Starting: electrical or manual

Electrical part (alternator)

• Output voltage: single-phase 230V or three-phase 400V.

Caution: some generators operate at a voltage of 240/415 V instead of 230/400 V. You are recommended to avoid using 240 V power sources as far as possible, since the voltage limiters used by MSF are set to a nominal voltage of 230 V maximum. They cut off at 245 V and reset when the voltage drops back below 235 V. With a 240 V installation, the limiter may never reset, unless you change its setting.

• Single-phase or three-phase. If you have some devices that will run only on three-phase current, it is essential to have a three-phase source. In all other cases, three-phase can be considered for powers above 10 kVA, although needing more than 10 kVA is not by itself enough to justify this solution. The size of the electrical setup and the distribution of power must make it potentially worthwhile (reduced cabling costs, use of one phase as a permanent circuit etc.). Be aware of the limits and constrains of three-phase: it is difficult to distribute the loads between the phases in a balanced way, and so to take advantage of the whole available power; and the power that is available for single-phase loads is limited to a third of the total power (e.g. a three-phase generator of 10 kVA cannot supply a single-phase load over 3.3 kVA).
• Power in kVA.The is a difference between prime and standby outlet power.:
• Prime Power (PRP): A generator can run unlimited hours annually with an average load profile that does not exceed 70% of the prime power rating. The prime power rating is the one that should be used when sizing a generator.
• Standby Power: A generator can run for 500 hours annually with an average load profile below 70% of the standby power rating. This rating is used on most generators' nameplates and labels. The standby power rating should not be considered for sizing a generator.
• Regulator (AVR): system which maintains the output voltage around its nominal value during power consumption fluctuations when stopping and starting appliances.Regulators are more and more often electronic. Magnetic regulators are more expensive and less accurate, but far more reliable.
• Integrated circuit-breaker. When the generator is overloaded, the voltage drops significantly, which may damage equipment.

Noise and soundproofing

In order to maintain good relations with your neighbours, it is best to avoid annoying noise levels.

The sound power level of a generator (LWA) is expressed in dB(A) (A-weighted decibels). The perceived sound level at a given distance from the source (sound pressure level) is also expressed in dB(A).

The average sound power level of an open generator is 105 dB(A), which translates to:

• 93 dB(A) at 1 m from the generator
• 85 dB(A) at 4 m from the generator

• Conversion of sound power level to sound pressure level
• dB(A) at 1 metre = LWA -12
• dB(A) at 4 metre = LWA -20
• dB(A) at 7 metre = LWA -25
• dB(A) at 10 metre = LWA -28
• Sound levels
• 0 to 20 dB(A) : almost inaudible
• 30 dB(A) : sleepy area in a quiet city
• 50 dB(A) : normal conversation
• 60 dB(A): supermarket, office
• 80 dB(A): annoying sound level (factory)
• > 85 dB(A): sound level which can cause hearing problems in the event of prolonged exposure
• 130 dB(A): invariably harmful sound level = pain threshold
• Soundproofing

There are several solutions to reducing the sound level of a generator:

• Choose a generator which is soundproofed by means of a factory-fitted hood. This reduces the sound level to 85 dB(A) at 1 m (= LWA of 97 dB(A)).

• Soundproof the generator house:
• Place noise attenuators on the air intake and outlet.
• Soundproof the access door.
• Add an extra exhaust silencer.
• Cover walls and ceiling with insulating material (such as rock wool). This reduces the sound level to 75 dB(A) at 1 m (= LWA of 87 dB(A)).

Caution: soundproofing is never inexpensive!

INSTRUCTIONS FOR USE

Motor-driven electrical devices require more power for starting than for normal operation. This should be taken into account when designing the system.

Connecting and disconnecting devices creates short voltage fluctuations which are minimized by the generator's built-in regulator. These variations may affect sensitive devices. It is sometimes necessary to install a voltage regulator/stabilizer.

ADVICE FOR LOCAL PURCHASE

For maintenance and transport reasons, local purchase is often the best solution. Before any local purchase, pinpoint your needs and contact your technical department for advice.

Criteria to be taken into account when considering the available options:

• Select a well-known and well-represented international brand: Caterpillar, Perkins, FG Wilson etc.
• Look for a supplier recognized by the manufacturer (importer or official dealer).
• Make sure that the assembly (engine/alternator/chassis) is either original or conforms to the original assembly.
• Find out if it is possible to set up a maintenance agreement and make sure that original spare parts are available. Also check the availability of spare parts in Europe, since local availability is never certain in the long term.

If these criteria cannot be met, it is better to order through your supply centre.

Generators might be considered as dangerous goods for transport:

• if a shipper or supplier provides written or electronic documentation stating that a flushing and purging procedure for flammable liquid powered engines has been followed in compliance with Special Provision A70 the generator is not subject to IATA DGR regulations
• if not complying with Special Provision A70 then the generator must be managed in compliance to IATA DGR regulations

The minimum to know about generators above 8 kVA (6.4 kW)

Specifications

Engine

• Diesel
• Engine speed: 1500 (preferred) or 3000 rpm
• Fuel water retention filter and pre-filter
• Hour counter
• Automatic shut-off in case of overheating or low oil
• Compensator between the exhaust outlet and the exhaust pipe extension
• Electric starter with 12 V battery

Electrical part (alternator)

• The choice between single-phase or three-phase should ALWAYS be discussed with your technical department. Three-phase is recommended for generators above 12 kVA (standard configuration = 400 V between each phase and 230 V between one phase and the neutral).
• 1 ammeter per phase
• 1 voltmeter per phase or circuit breaker between the phases
• 1 frequency meter
• 1 earth connection

Safety panel

• 1 main circuit breaker (thermomagnetic)
• 1 differential circuit breaker
• 1 emergency stop button

Instructions for installation

If more than 8 kVA, a generator is considered to be stationary (i.e. not transportable by 2 people) and should be placed in a plant room ("generator house").

The dimensions of the room should take into account the space needed around the generator for its maintenance.

The ground should be level to prevent premature wear of the alternator and cemented to protect the engine from dust and prolong its lifespan.

A fixed generator should be installed on a rubber carpet (or other vibration- and sound-absorbing material) and bolted to the floor.

It should be connected to the appliances with permanent connections, via an electrical switchboard.

Exhaust

The exhaust pipe must follow the shortest route to the outside, but must not be on the same side as the air intake.

A flexible steel pipe (compensator) is required between the exhaust outlet and the exhaust pipe extension to absorb the engine vibrations.

The diameter of the exhaust extension should be related to the size of the engine (see manufacturer's standard).

Ventilation

As the lifespan of the engine depends mainly on effective cooling, you are recommended to place the generator diagonally between the air inlet and outlet, in order to maintain good circulation between the cool air (below) and the hot air (above), as in the diagrams below.

Avoid installing the air outlet facing into the prevailing wind. If this is impossible, provide diversion ducts.

If plant room temperature increases excessively, you are recommended to install an extractor fan on the air outlet. The capacity of this fan should be related to the power of the engine and the level of the outside temperature.

Ideally, order an extractor fan which will start automatically with the generator.

INSTRUCTIONS FOR USE

Always take care to switch off all appliances being powered by the generator before starting or stopping it.

Minimum load

Manufacturers stipulate that a generator should not run under 30% of its rated capacity (for example, a 20 kVA generator should have a minimum load of 6 kVA).

A generator running at only 10% or 20% of its maximum load cannot actually reach its operating temperature. The exhaust gases are too cold, leading on one hand to excessive oil consumption (= poor efficiency) and on the other to carbon deposition (= premature wear).

Maximum load

It is not recommended to run a generator at 100% of its capacity, at least not all the time. To prevent any risk of premature wear, the maximum load should not exceed 80%.

Phase balancing

The total load on a three-phase generator must be distributed over its three phases. One single phase can provide only one-third of the generator's power (using the generator ammeter, you can measure the average power demand made by the load and then calculate the power demand on each phase).

For the power calculation, you should take into account the decrease of output power if the altitude exceeds 1000 m or the temperature permanently exceeds 35 ºC (contact your technical department for how to calculate these 2 factors).

Start-up current

The starting of motor-driven appliances causes a surge in current which can reach 8 times the normal capacity and trip the thermal cutout. It is thus essential to bear this in mind when deciding on the power of your generator.

SAFETY MEASURES

• A generator must be protected against the elements.
• The generator plant room should be locked and only the person in charge should have access.
• As electrical accidents can have fatal consequences, it is strongly recommended to install a residual current circuit breaker on the generator outlet in order to protect users and electrical circuits (300 mA for generators > 8 kVA).
• Install a fire extinguisher and a sand bucket near or inside the generator house.

MAINTENANCE

1500 RPM GENERATORS

• Service A : EVERY 200 HOURS
• Clean engine
• Change engine oil
• Drain fuel filter water tray
• Clean air filter
• Service B : EVERY 400 HOURS
• Service A
• Change fuel filter
• Change oil filter
• Service C : EVERY 800 HOURS
• Service B
• Change air filter
• NB: the air filter must be changed sooner if the engine is running in a confined or dusty space

3000 RPM GENERATORS

• Service A : EVERY 100 HOURS
• ​​Clean engine
• ​​​Change engine oil
• Drain fuel filter water trap
• ​Clean air filter
• Service B : EVERY 200 HOURS
• Service A
• ​Change fuel filter
• ​Change oil filter
• Service C : EVERY 400 HOURS
• Service B
• Change air filter
• ​NB: the air filter must be changed sooner if the engine is running in a confined or dusty space