Andrio Electrical Generator
Standby Generators
Please take note that we do not supply and install generators!
Overview
Please take note that Andrio Electrical does NOT install generators since it is not our core business so please do not contact us for generator quotations. However, the information on this page will give you valuable insight into generators in general and you will realise the importance of balancing your distribution board.
If you are considering installing a power back-up for your business you will have to decide whether it is going to be a generator, a UPS system or a combination of both. Each one has its pros & cons and it is in your own best interest to learn as much about the subject as possible before you jump in.
Aspects to concider when installing a generator
Noise - Open generators are extremely noisy and if noise cannot be tolerated it will have to be a "silent" type with an enclosed canopy and/or mounted within a dedicated room to minimize noise pollution. Silent generators are more expensive and generator enclosures are normally sold as optional extras.
The Installer - Always ensure that you deal with a reputable company with references to avoid potential problems. It is in your best interest to enlighten yourself as much as possible about the technical aspect of generators, their pricing, etc.
Location - It is wise to install the generator as close to the main distribution board as possible so as to reduce costly cable runs. The room must be of adequate size to allow for servicing and repairs. An existing room may have to be altered or a new one built.
Vibration - It may be necessary to install shock absorbing material or a coil-spring loaded bed onto which the genset is mounted to reduce vibration within a building.
Fuel Storage - Your generator may be of a size that necessitates the installation of a dedicated fuel storage tank and you may have to store additional petrol or diesel in drums. There are particular regulations for the storage of fuel with regards to ventilation & fire.
Fire - You may have to install a fire detection system, a fire hose and/or fire extinguishers.
Cooling - Depending upon the size of the genset you may have to install a dedicated water cooling system with reservoir tank & water circulating pump. Most modern units have onboard radiators.
Ventilation - Very important if mounted indoors. As there will be diesel exhaust fumes you will have to install an extraction fan with exhaust piping to suck it out into the atmosphere without re-introducing it back into the building.
Weight - If you intend installing the unit on a floor other than the ground floor or solid ground consideration must be given to the load-bearing capability of the floor on which it is going to stand. Every multi-floor building is designed and built with a pre-determined "Kilogram per square meter" load-bearing capability. If you don't know yours find out from the designers or architect. Example - If a generator weighs 2500 kilogram and has a footprint of 3m x 1.5m it may well exceed the load-bearing capability of the floor (say 450Kg per sq/m).
Maintenance - You will have to periodically run your generator on load and in addition you will have to enter into a service contract with a reputable company to service both the diesel/petrol machine and the alternator connected to it.
Power Lag - When a power failure occurs the generator will start but it will take approx. 10 to 15 second before the unit comes to full operational speed and power is restored. During this time everything will be completely off unless you have a UPS system installed.
General technical Tips
Prime Power Rating – This is the power (KVA) that a particular generator can generate continuously, 24 hours a day, seven days a week. Purchase your generator based on its Prime Power Rating.
Standby Power Rating – This is the power (KVA) that a particular generator can generate during a short spurt (peak). The Standby Power rating for an engine is always higher than its Prime Power Rating.
Kilowatt (KW) is measured at 85% of the Prime Power Rating, thus KvA x 0.85 = KW. The KW rating of a machine will always be lower than its KVA rating. It is generally accepted that a generator runs best with a load of around 80% of its full load capacity which will help in preventing the undue build-up of sludge & dirt within the engine and excessive carbon deposits in the alternator. Too little load is not good and even periodic test-runs should be performed under full load conditions. Petrol generators are normally used in single phase installations and diesel generators in three phase installations.
Once you have made the decision to install a generator the next thing that you will have to do is to perform a load test on your main distribution board. This will determine the size of the generator required and must be done. More often you will measure the highest load on the red phase but this is not always the case.
Balance your Distribution Board
It is normal to have a variance between phases but if the load differs significantly from phase to phase you should get an electrician to rewire the distribution board and balance the various circuits to achieve a more even spread across the three phases. If your distribution board is unbalanced you may end up buying a much larger generator than what is really necessary. So, ensure that it is well balanced before you do the final load test.
Here is an example:
A. Measure initial load. Total load = 321 Ampere (Unbalanced with a peak of around 150 Ampere - Not Good!)
Phase 1 (Red) to Neutral - 150 Ampere
Phase 2 (White) to Neutral - 73 Ampere
Phase 3 (Blue) to Neutral - 98 Ampere
Neutral - Constant return of the three phases
B. Measure the same load again following balancing of circuits. Total load = 321 Ampere (Balanced with a peak of around 110 Ampere - Good!)
Phase 1 (Red) to Neutral - 110 Ampere
Phase 2 (White) to Neutral - 104 Ampere
Phase 3 (Blue) to Neutral - 107 Ampere
Neutral - Constant return of the 3 phases
You will see from the diagram above that in the case of the unbalanced distribution board on the left that a generator will be required to handle the peak of 150Ampere whereas if the load was balance as it is on the right a much lower peak can be maintained which will result in a smaller generator.
Don't worry about three-phase motors as these will be naturally balanced and cannot be altered. Just remember to run them when you're doing the load test. Also, when determining the size of a three phase or single phase generator a similar approach should be followed. Just apply the relevant calculations.