There’s a wide range of diesel generators on the market, but this choice can be narrowed down considerably by answering a few questions.
Stand-by or Prime?
A prime generator is intended to be the sole power source, while a stand-by generators are built to kick in to provide normal utility power in short bursts. Typically, a prime genset will be derated by 20% to give some leeway when running for long periods.
Fast or Slow?
AC power switches the current flow switches back and forth between polarities (positive and negative) at a set rate: 60 Hz (times per second) in North America and 50 Hz in Europe and parts of Asia. To get this frequency, the generator is designed to run at a set RPM, typically around 1,500 or 3,000 RPM. High RPM generators provide more power for the size of the device, making them better for portable applications. Low RPM gensets are quieter and last longer.
One phase or Three Phase?
In a three phase system, the phases are staggered so that the total voltage stays relatively uniform as the current switches polarity. 220V devices like welders are usually designed for this type of even current. A one phase genset can handle household appliances, but high power devices like dryers and electric stoves really need a three phase system.
Household power is either 110v or 220v, which is supported by most small generators. However, some gensets can only output one of these voltages at a time. Heavy duty systems have higher voltage outputs that must be transformed into household voltages before use.
Noise reduction capabilities?
Many cities have codes limiting generator noise 70 db, and may require the genset to be mounted inside a sound blocking enclosure, regardless of the open air sound level. Some systems have a “critical” muffler built into the exhaust manifold, while others have the option of adding a bolt-on muffler.
How much electricity do I need?
The power factor is the difference between the rated power and the actual power available. The general rule of thumb is to figure on getting 80% of the rated output due to inefficiencies in the electrical system. A genset will be rated in watts, kVA (kilovolt amps) or both. The kVA figure takes the power factor into account, but the wattage rating does not.
Power output should be calculated by determining how many watts would be used if every device in the system kicked on all at once. Induction motors like those used in refrigerators, washing machines and sump pumps need two or three times their rated output to start.
Anyone in the market for a diesel genset would do well to check out Allight Sykes’ range designed to cover all applications and power output needs. Their reputation is famous across the world.