Published: 1 year ago
Contributed by Electrical Generating Systems Association
From the July/August 2014 issue of Today’s Facility Manager
The majority of emergency and standby generator sets are programmed to start on a weekly exercise cycle, and run, in most cases, for a one-hour period. This may be considered a good test of the engine’s starting system (battery, charger, block heater, and fuel system), because that is all that is being tested. The generator’s ability to produce electricity, the circuit breakers, voltage regulators, and automatic transfer switch (ATS) are not being tested unless the ATS transfers the facility from utility to the generator set after the programmed start. Most facilities choose to run the generator set “unloaded.”
There are two potential problems that can compromise the reliability of the standby generator set. The first is that without testing the complete system under expected working conditions, any problems in the system will not be uncovered until there is a utility power failure. Second, continued operation under no-load conditions can lead to “wet stacking” of diesel engines. This is a condition resulting from condensed fuel and oil particles accumulating around the injectors, valves, and exhaust system, reducing the engine’s ability to generate its rated load.
A load bank is an important tool that will test a complete generator set system up to its rated load. This testing should be performed, at least, on an annual basis. How can facility managers (fms) be sure that they know what they need to know?
Carmen Nosic of HPS Load Banks says, “Before you schedule your next load bank installation, review these four planning tips to ensure your next load test runs smoothly. Whether you are using a resistive reactive load bank or resistive only load bank, the success of your load test depends on your location, cable, external power and the load test personnel. Overlooking any of these critical components can result in fines; cause delays in your schedule, and may result in injury.”
Location: Both resistive/reactive and resistive load banks emit massive amounts of heat and exhaust, which exit each unit via a side discharge or top discharge, depending on the type of load bank. To maximize safety, ensure each load bank has adequate airflow and space around the unit to minimize risk of injury and fire.
Cable: One of the most significant elements in load testing is having the right cable for the load bank set up. Regardless of the type of load bank, long cable runs and multiple connection points can result in loss of amperage, increasing cabling needs and testing expenses. Minimize additional costs by shortening the cable runs and connection points. Ensure cable run is in a secure location to reduce the risk of theft and loss of connectivity.
External Power: Having external power is not typically required. Fans and controllers can be powered right off of the buss on select load bank units. By running off the buss, a load test team will have a quicker set-up time and eliminate the need to rent a generator and locate shore power. One potential issue to consider is that fans and controllers will lose power if the unit being tested experiences a power failure. Should a load bank lose power, it will undergo an immediate hot shut down, and testing data will be lost. Make it a point to check with the load bank provider prior to the load test to see if the unit is built to handle a hot shut down.
Personnel: Using qualified personnel is critical to the overall success of a load test. It is imperative for a qualified operator/technician to have a complete understanding of the load bank unit (specific make and model) being used to ensure proper set-up and operation during the test. Review the state, county, and local regulations to verify that testing personnel meet mandated qualifications. Each test administrator should be equipped with the skill set to administer a load test, operate the load bank in harsh weather conditions, and test preset capabilities using a laptop or a handheld controller from up to 150 miles away. Additionally, each testing team member should have a clear understanding of how the load bank will handle an unexpected hot shut down.
“Remember that load banks can be extremely dangerous if operated incorrectly. Most load bank manufacturers offer free operator training to rental and sales customers. Contact the local load bank manufacturer or rental specialist with questions regarding load bank specifications, local load testing requirements, and upcoming operator training classes on specific load bank units,” Nosic adds.
Knowing what cooling options are available and the benefits of each can be important. Dave Pfister of Simplex Load Banks & Fuel Supply Systems says “making the proper choice for load bank placement is essential to providing an adequate supply of ambient air for proper cooling. Always be sure the exhausted hot air will flow away from the load bank, and not be recirculated back to the system and potentially cause an overheating problem. Since most load bank systems are cooled with an integral forced air cooling system, it is very important to inspect the area around the air intake before each use.”
Pfister continues, “Although many portable load banks can be horizontally or vertically cooled, many larger resistive stationary systems are vented vertically with cold air intake at the bottom and hot air exhaust out the top. Any paper or debris that could block the air intake should be removed so the system is not inhibited.
The same care should be given to load bank air exhaust. Before each use, remove any debris that may restrict flow of hot air away from the system. Since exhaust air temperatures for air cooled load banks can get very hot, it is very important to keep persons and property away from the airstream to avoid injury or damage.
Many load banks also offer malfunction protection systems to detect problems such as fan failure, high exhaust temperature, and high air intake temperature. When a malfunction is detected, an alarm can be tripped and the system automatically shut down.
For environments requiring ‘pin drop’ quiet operation, a water cooled load bank offers a highly attractive alternative to the cooling fan noise that accompanies traditional air cooled units. Water cooled load banks are perfect for indoor installations in controlled environments versus outdoors where units are exposed to elements. Besides being completely quiet, the unit is compact and virtually maintenance free. Water cooled units are also ideal for installation in buildings in central city areas, industrial parks, or office complexes where an outdoor air cooled unit would be architecturally obtrusive or impossible to install due to space or noise restrictions.”
Other external conditions can drive the decision for load bank testing. According to Cory Fones of ComRent International, “New Tier IV engine regulations force generators to require a specific base load to operate efficiently enough to meet the emission standards. Low and inconsistent base loads can create operational issues which could result in expensive repairs and sub-par reliability to the end user. One effect of having inefficient load is that it does not allow it to reach operating temperatures for the catalyst to burn and emissions standards are not met. In addition, the operational issues can range from clogged EGR valves to turbo issues to extensive wet stacking.”
He continues, “There are load banks designed with key features to run in parallel with the generators and address these concerns in specific environments by providing the necessary base load to help prevent these issues from occurring and to ensure the Tier IV generators are meeting the emissions standards.”
Fones continues, “A reactive or inductive load bank test is most often seen at the factory or on-site during new installation startups. However, some facilities with larger motor loads would warrant testing power systems with reactive load to ensure it will handle real-life like loads.
When resistive load is applied with inductive load you can achieve a .8pf. This will allow you to simulate a real-life commercial load that can consist of lights, heaters, motors, pumps, etc. that would create a reactive load. Using a reactive load bank is how you will achieve a full load test to the nameplate rating on a generator. This can be provided as a separate reactive load bank in parallel with the resistive load bank or offered as one resistive/reactive combination load bank.”
Fms know the challenges of code compliance, and they can often turn to suppliers for assistance on this. This ensures the product and services chosen are in compliance, or assist with compliance.
According to Kurt Summers of LoadBanks of America, “Testing your emergency generator has critical requirements which are time sensitive. You should ask local authorities for help in determining exactly what is required. Tests (using building loads as well as using portable load banks) are often recommended and may be a requirement, depending on facility type. Ultimately, choosing a routine of maintenance and testing can ensure your generator system is compliant, but more importantly, can provide you with peace-of-mind, knowing your generator will perform when needed.”
Another consideration is to use radiator duct mounted load banks in packaged diesel generator set applications. Supplied as an integrated part of packaged diesel generator sets, radiator duct mounted load banks offer cost-effective load testing solutions for routine maintenance testing of standby emergency power systems.
Martin Peko of Load Banks Direct adds, “Unlike outdoor stationary load banks which are installed on a separate concrete pad equipped with integral cooling systems and remote operator controls, radiator duct mounted load banks are open-frame construction, directly coupled and mounted in-line with the engine radiator cooling system making it an integral component of the generator set. They utilize airflow from the engine radiator fan to cool resistor load elements, are sized to absorb a balanced resistive load at unity power factor, and are typically rated 50% of generator set nameplate KW rating.
The engine generator set packager provides a complete integrated system equipped with load testing capability. Simplified installation, smaller installed footprint, and reduced installation wiring contribute to an economical load testing solution, which allows fms to meet load testing demands of standby emergency power systems and minimize the adverse effects of engine wet-stacking.”
Peko adds, “Wet-stacking is the build-up of unburned fuel deposits from running diesel engines under lightly or no load conditions which, over time, leads to increased engine emissions, reduced engine capacity, increased maintenance costs and premature engine failure.”
Regarding technology and innovations in the load bank industry, Mark Prevoznik of Avtron Load Banks has this to say, “As the components of the emergency backup power system become more sophisticated in regards to the communication, networking, and building management system interface, the role of the load bank has also changed. [These] are no longer considered an auxiliary piece of equipment that can be used ‘as needed’ in emergency backup systems, but as an important integral part of the critical power management system (CPMS).”
Prevoznik adds, “Load banks used in today’s emergency backup systems typically feature remote I/O, Modbus protocol, software control, sight load correction, and network capability. These features are required on all load banks used in CPMS applications and apply for either a portable or permanent (fixed location) type load bank.
Load banks that are permanently installed are typically rated at a single voltage (480V is typical) and kilowatt (2000 kilowatt is typical) capacity and are required to have either remote or software control. Permanent load banks are also on-site 24/7 along with the other critical backup power components like the generator set, switchgear etc. This allows the facility manager to include the load banks as part of their regular testing and maintenance schedule.
Portable load banks however, can be moved to various locations and should have multiple voltage (208, 240 and 480V) and kilowatt (0 to 700 kilowatt is typical) capacity along with the ability to network or daisy chain with other portable load banks. The ability of portable load banks to daisy chain gives the facility manager flexibility in regards to overall kilowatt capacity and voltage selection.”
The Electrical Generating Systems Association (EGSA) has been a resource for members of the on-site power industry, including facility managers and engineers for 49 years.
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