Frequently Asked Questions and Answers About Generators.
Understanding Home Standby Generators:
An average home may use more than a hundred electrical appliances and devices to provide convenience, comfort, and security. It is, therefore, essential that we install a backup home generator to prepare for a power outage. A residential generator has major advantages over a portable gen set- automatic-start, permanent fixture, more power, cleaner fuel (natural gas or propane), low running costs and all-weather operation. Standby power systems start automatically with seconds after a home’s electricity goes out and ensures a continuous electrical supply.
A Transfer Switch immediately senses when power is interrupted and transfers power generation to the generator. It also senses when power is restored and transfers the load back to the utility source and signals the generator to shut down. The power generator is installed outdoors and linked directly to the home’s permanent fuel supply.
Typical Installation:
A residential standby generating system typically has three basic elements: a generator, a transfer switch and a service entrance breaker.
1- Generator
Generator – Produces electricity for essential or selected systems like cooling, heating, refrigeration, security, and lighting. Your backup needs, simple or more extensive, determine the size and output of the unit.
2- Transfer Switch
Transfer Switch – Immediately senses when power is interrupted and transfers power generation responsibility to the generator. Senses when power is restored and transfers the load back to the utility source and signals the generator to cool off and shut down.
3- Service Entrance Breaker
Service Entrance Breaker – Provides protection to your transfer switch, internal breakers and circuits and generator due to electrical strikes and power surges.
How the System Works:
Transfer switch monitors voltage coming from the utility
Transfer switch senses when utility power fails or drops below an acceptable level (brownout), and sends a signal to start the generator
Transfer switch automatically disconnects the utility power from the electrical circuits in your home and reconnects them to the generator
The generator continues to supply electrical power to your home until utility power is restored
Transfer switch senses when the utility power is restored automatically disconnects the generator from your home circuits and reconnects the utility power
What Happens When The Power Goes Out?
Power Outage Occurs:
When utility power voltage falls to less than 85% of nominal or fails entirely, the standby power system will automatically go through a start sequence and connect to a home. The transfer panel control constantly monitors the power quality from both the utility source and the generator set. When the transfer panel control senses unacceptable utility power, the control waits for 3 seconds and then sends a signal to start the generator set engine. If the utility power returns before 3 seconds have passed, the generator set engine will not be signaled to start. When the start signal is received, the engine starts and reaches the proper operating speed and AC power is available at the generator set. The transfer panel control senses this waits for 3 seconds and will then transfer the generator set power to the home through the transfer panel contractors. This sequence of operations will usually occur in less than 10 seconds from the time the power outage occurred to the time when the generator set power is connected.
Utility Power Returns:
When utility power comes back on and returns to your home, the transfer panel control senses this and will watch for acceptable voltage. After checking for acceptable utility voltage for five minutes, the transfer panel control will signal the transfer panel contractors to re-transfer the load back to the utility source and disconnect the generator set source. At this point, the generator set is “off-line” and will be operated automatically another five minutes to properly cool down. After the cool-down cycle, the generator set will be turned automatically off and reset to standby mode
Few Terms Used In Generators:
1- Operating Speed
Gen-sets are normally governed to fixed speedrunning. 1500 rpm to produce 50Hz electrical supply for the European market and 1800 rpm to produce 60 Hz for the US market. 60Hz supply can be achieved at 1200Hz with some alternator sets- this is uncommon.
2- kW
Kilowatts electrical is a measure of electrical power produced by a gen-set. 50Hz generator sets are usually marketed in terms of kW.
3- kVa
Kilovolt amps is a measure of electrical power produced by a Genset. 50Hz gen-sets are usually marketed in terms of kVa. As gensets produce an alternating current P=VI doesn’t hold true. Voltage and current follow sinusoidal waveforms with a phase shift due to the reactance (generated by inductance & capacitance) of the load on the alternator, and hence a power factor is used. Industry assumes a 100% resistive load for which a 0.8 power factor is used. This relates kWe to kVa by the following:
4- kW = kVa x 0.8
Fuel Coolers
Gen-sets are normally fitted into a frame, which holds a small fuel or “day tank” for a limited time running. If the gen-set operates in elevated ambient temperatures, or the engine has a high fuel spill ratio, the temperature of the fuel will often be controlled by a small fuel cooler (air-to-fuel) mounted on the cooling group. The cooler prevents rises in “day tank” temperatures preventing fuel injector damage.
5- Fans
All Electronics are fitted complete with fans to provide cooling to the radiator and charge cooler if fitted. Two versions of fans are normally offered for gen-sets and IOPU’s, pushers (which blow air through the radiator) and pullers (which pull air through the radiator). The customer is able to specify the type most relevant to their application/installation. The type of fan used will affect the ambient air temperature the bulk of the engine will see and may have consequences on the engine’s rating and performance.
6- Emissions
Genset emissions are complicated and specific to the country in which they operate. Generally, requirements are less demanding than other off-highway equipment but are often driven by marketing rather than legislative needs. Legislative limits are complicated, determined by introduction date, engine powers, and power rating. The three most important limits are listed below with links to sites where full documentation can be found.
Common Questions?
Q1: What happens if I underload a generator?
Ans: All engines are designed to operate under varying load, ranging from the maximum down to the minimum. Problems occur when light loading (min load) is sustained for long periods of time resulting in the engine not getting up to its normal temperature. Oil in the cylinder that is normally burnt is heated and lacquer is formed on the cylinder liner. If the light loading continues, visible blue smoke will appear and the engine will require service work to deglaze the liner or replace it.
Q2: Where can I get parts for my generator set?
Ans: If you buy or own a Enpower generator set you will be able to purchase any spare parts you require from our local dealer in your area. ENPOWER network of dealers stock a wide range of parts for our generator sets and should be able to provide you with the items you need.
Q3: When and how do I service and maintain my generator set?
Ans: The frequency and type of service required to maintain a Power link generator set will depend on a number of things including the usage of the generator, the environment that it operates in and the percentage load that it carries. Ensuring that a full service is carried out regularly is the responsibility of you as the owner. You will need to carry out frequent visual inspections every two to three months to check that things are functioning – any faults or repairs that you note should be passed on to your local Power link dealer. A full service including a change of such things as filters and lubricating oil should be carried out every twelve months. Most failures to start-up are the result of the set not having been regularly tested. We recommend that you check your generator once a week.
Q4: Will a generator be noisy?
Ans: All generators produce some amount of noise from the exhaust, the engine, and the airflow. Power link generators are designed to provide maximum noise control and are all noise level tested during production to ensure they meet relevant legislation. Our generators can be supplied with Sound and Super Sound Attenuated canopies that help to absorb excess noise. Can a generator set be used during adverse weather conditions? Power link generator sets are designed to function in hostile environments and during extreme weather conditions. To extend the life of a generator and to prevent such things as shorting and rusting, if possible they should be protected from the elements.
Q5: How long can a standby generator be continuously operated?
Ans: There is no set answer to this question. Power link generators are designed to last for long periods of time and function in heavy-duty operations. However, it is important that the set is inspected regularly between each use, before restarting to check such things as fuel and oil levels and any signs of abnormalities. Our sets can run continuously when the amount of load is lowered.
Q6: How long will a generator run on a tank of fuel?
Ans: The amount of time that a generator will run on a tank of fuel depends on the size of the tank, the amount of time in which the generator is in use and the load that the generator has to fulfill. All Power link generator sets are designed to run for eight hours at their full rated load.
Q7: What is a transfer switch?
Ans: A transfer switch is a panel that is wired into the premise’s electrical distribution system to allow a generator to be used. It prevents the generator from back-feeding into the mains power supply which could cause serious injury to line workers trying to restore utility power supplies. Power link currently supplies two types of transfer switches: manual and automatic.
Q8: How does a generator set work with the mains electricity supply?
Ans: An alternator of a generating set can be protected in three different ways: A) thermal-magnetic protection The TMP protects the alternator against overload and short circuit. In case of overload, the TMP shall switch off after a determined period of time. This period of time depends on the kind of overload: the higher the overload, the shorter the time needed by the TMP to switch off. In case of a short circuit, the TMP always switches off immediately. B) Earth leakage protection The ELP automatically interrupts the circuit when an earth leakage failure occurs between (a) phase(s) and the earth which exceeds 30, respectively 100 or 300mA, depending on the type of earth leakage switch used. The ELP protects persons against electric shocks in case of indirect contact. Moreover, the ELP also serves as a protection against short circuit. An earth pin is required in most cases! C) insulation protection An insulation protection relay is used to measure and guard the insulation (resistance) between not earthed AC- mains and a free chosen earth (= the frame or the mass of the generating set). In this way, the user is protected against undesired contact with the AC- mains. When an insulation default occurs the tension of the alternator can be interrupted, the engine can be stopped or an alarm can be activated. An earth pin is not required here!
