Frequently Asked Questions
In our line of work we get a lot of questions and we are happy to answer them. But as a service for you we have gathered some of the most frequently asked questions that we get and we’ll give you the answers below. If you still haven’t found the answer to your question, don’t hesitate to call us.
PRP – Prime Power is defined according to ISO8528-1 as the maximum power output that a generator set can produce continuously when connected to a variable load for an unlimited number of hours a year, as long as the maintenance intervals and procedures are being carried out as prescribed by the manufacturer. A prime-rated generator set is limited to a 24-hour average load factor of 70%, if not stated otherwise by the manufacturer.
LTP – Limited Time Power is defined according to ISO8528-1 as the maximum power output that a generator set can produce for up to 500 hours a year, as long as the maintenance intervals and procedures are being carried out as prescribed by the manufacturer.
ESP – Emergency Standby Power is defined according to ISO8528-1 as the maximum power output that a generator set can produce when connected to a variable load for a maximum of 200 hours a year, as long as the maintenance intervals and procedures are being carried out as prescribed by the manufacturer. An ESP-rated generator set is limited to a 24-hour average load factor of 70%, if not stated otherwise by the manufacturer.
COP – Continuous Power is defined according to ISO8528-1 as the base load power output that a generator set can produce at a constant load for an unlimited number of hours a year, as long as the maintenance intervals and procedures are being carried out as prescribed by the manufacturer.
According to legislations within the EU all generator sets that are subject of movement at least once a year and are below 560kW of mechanical power output from the engine must fulfill the demands in EU Stage III A emission requirements. If the generator set isn’t subject of movement at least once a year or have a higher power output than 560 mechanical kW the generator set doesn’t have to comply with Eu Stage III A.
The most commonly used fuel in Sweden for backup power is environmental diesel of class MK1 B0. The B0 indicates that there are 0% RME and/or FAME in the diesel. Most suppliers also accepts synthetic diesel like EcoPar. If you are to use any other type of diesel fuel for your backup power, please be careful and check with the vendor if that fuel type is approved, you may experience power deterioration and/or shortened service interval.
As a rule of thumb a generator set uses 0.25 liters an hour and electrical kW produced.
When discussing the fuel system that you as a customer want installed with your backup power the first thing to think about is the running hours that you would like to have, without the need for refueling. If you have a small generator set and/or a low number of running hours needed it normally is enough to install a day fuel tank within the room/container. If you have a larger generator set and/or have the need for a high amount of running hours we normally install a day fuel tank and an external fuel storage tank. The generator set is connected to the day fuel tank, which is filled from the external fuel storage tank. Filling of the day fuel tank is handled by a fuel transfer pump system. Our fuel transfer pump system is fitted with dual pumps and a control system making the system redundant.
Normally all our fuel tanks are within a spill tray or dual walled.
One of the most frequentely asked questions that we get is regarding air inlet and outlet openings and the need for ventilation and combustion air. Generally, as a rule of thumb, the generator set needs bigger openings than you might expect.
A generator set with a direct driven fan and radiator mounted to the base frame has been fitted with a fan big enough to produce enough cooling air both for the engine cooling and the ventilation of the heat rejection to the room. The amount of air that the fan pushes over the radiator plus the amount of combustion air the engine needs is the total amount of air that you have to transport in to the room/container over the air inlet openings.
Generally when calculating the needed openings we calculate using a maximum speed over the inlet grills and louvers set to 4 meters a second. By not exceeding this air speed you will prevent snow, water and dust to be sucked in to the room/container. You also have to remember to adjust your numbers according to the grills flow dampering specifications. Normal grills reduces the free opening with 35% and a sound-proofed grill reduces the opening with 75%.
The outlet air opening normally is the same size as the radiator. The outlet air can have a higher air speed thus giving the advantage of smaller openings. But it always is necessary to calculate the back pressure over the fan. If you have a back pressure higher than the vendor has approved, you might have a reduction in power output from the generator set.
When using coolant coolers with your generator set, the aspiration of the engine is important to have in mind. If you have a water cooled aspiration you only have to fit that cooling circuit with a coolant cooler, but if you have an air cooled aspiration you probably will need to install a heat exchanger. Also be adviced, a heat exchanger might be needed if the distance and/or the lifting height is to big to handle for the engines internal water pump.
If you are using coolant coolers the heat rejection to the room still needs to be ventilated from the room, and the engine still needs combustion air. The air inlet openings will be significantelly smaller and the air outlet opening normally is small and fitted with a frequency-adjusted fan.
How often and how to test your generator sets often depends on the type of solution that you have and which test function that you have at your disposal. Some of the test functions may or will affect your daily operation and that might limit your opportunities to test your backup power.
Start test is the simplest test to perform. If you perform a start test the generator set will start but it will not control any breakers or connect the generator set to the load/grid. This test will make sure your generator set will start if needed and it checks the most common source of a failure, the batteries. Since you are not loading the generator set this tests should be only be performed once a week and not for a longer duration than a couple of minutes.
Load take Over is a test where the generator set starts and, if fitted with synchronization, will synchronize to the grid and than disconnect the incoming feeder from the grid. The generator set is now feeding the load. This test will test all involved components, such as the generator breaker and the mains breaker, and since the generator set is loaded it will reach normal running temperature. Hence, everything will be tested and the users most likely won’t even know that the generator set is feeding the load.
In parallel with the grid is almost the same as a load take over, but instead of disconnecting the incoming feeder the generator set stays in parallel mode. At this point you can adjust the power output from the generator set. If the generator set produces more power than the load consumes the excess power will be fed out on the grid. Be sure to inform the grid owner that you will perform the test, you need the approval from the grid owner to be able to do the test.
Simulated mains failure is the best test to perform, if you can allow a short blackout on the load. The test is initiated from the control system, just like all the other tests, and it will simulate an error on the incoming mains. The generator set will start up and disconnect the incoming feeder from the grid and connect to the load. The complete chain of events will be exactely as if you had an actual mains failure.
If you use the tests mentioned above and you perform your tests according to the recomended test intervals that we deliver with our solutions, your backup power will be in great shape and you can feel confident that your system will work when it must.
The control system is the brain of your backup power system. In automatic mode the control system will perform as expected in case of a mains failure and in manual mode you can control the chain of events. Today most of the control systems is based on a standard control panel from a vendor that has built and tested the panels to work as it should. The only thing we have to do is to adjust it to fit the customers needs and requirements. We noramlly use two of the most common panels on the market, DeepSea or ComAp.
When designing a control system the end user must specify what type of solution they want and what type of tests and functions they require. Do they need automatic mains failure start? Is it necessary to synchronize to the grid? Should the system communicate with a BMS (Building Management System)? If you as a customer can specify your needs we will help you get that, if you want our help determining your needs we will most certainly help you.