The Dangers of Neglect
Emergency power must be more reliable than the electric utility. While in some areas of the country this is not a tough assignment, an increasing number of emergency systems are failing because of neglect, bad placement or insufficient monitoring. But let's assume all components of the emergency power supply system (EPSS) have been designed and installed properly, and acceptance tests have been...
Emergency power must be more reliable than the electric utility. While in some areas of the country this is not a tough assignment, an increasing number of emergency systems are failing because of neglect, bad placement or insufficient monitoring.
But let's assume all components of the emergency power supply system (EPSS) have been designed and installed properly, and acceptance tests have been performed according to the latest edition of NFPA 110, Standard for Emergency and Standby Power Systems, and to manufacturers' standards. All systems should perform as designed whenever needed. Correct? Not necessarily.
Immediately after an EPSS is commissioned, its chances of not performing as designed in an emergency begin to increase dramatically for two reasons: first, ongoing maintenance and testing are not being performed as recommended by the manufacturer and by minimum NFPA 110 standards; and second, placement of EPSS components was bad.
Maintenance and testing should be performed according to NFPA 110, 8.1.1 which states:
The routine maintenance and operational testing program shall be based on all of the following: (1) manufacturer's recommendations (2) instruction manuals (3) minimum requirements of this chapter (4) the authority having jurisdiction [AHJ].
In addition, NFPA 110, 8.3.2 states:
A routine maintenance and operational testing program shall be initiated immediately after the EPSS has passed acceptance tests or after completion of repairs that impact the operational reliability of the system.
Unless the local AHJs have more stringent requirements, NFPA 110 is the "go-to" standard. There are several references to NFPA 110 in NFPA 101, Life Safety Code , regarding testing and maintenance of EPSS. NFPA 70, National Electric Code , only briefly mentions the subject in Article 700. Obtusely, NFPA 110, 8.1.1 refers to manufacturer's manuals which pass the buck back to the equipment maker.
At any rate, the maintenance and testing called for by the standard can be done by either trained in-house staff or by EPSS contractors. Most owners prefer a hybrid approach: routine weekly inspections and monthly testing are performed by employees, advanced major or annual tasks by outside contractors.
As of this writing, there are no certifications or licenses required for EPSS maintenance and testing, either by employee or contractors. This has drawn considerable criticism, especially at times when failure of emergency power has resulted in public services interruption, legal action, extreme inconvenience, and in rare cases, death.
In most cases maintenance personnel are tasked with varying responsibilities. Only one of these is the EPSS, composed of the generator (emergency power supply, or EPS), circuit breakers and automatic transfer switches (ATS). As a result, a relatively small amount of time is dedicated to maintenance and testing of EPSS. The most conservative, and often most expensive method is to have only factory or professionally trained technicians perform all manufacturer's suggested items. Given the litigious society we live in, it makes good sense to think about possible legal actions when deciding which avenue is best.
Legally required EPSS are installed for the protection of human life. Hospitals, for example, must be able to "defend in place," and the EPSS must therefore be independent of an electric utility in case of a disaster. NFPA 110, 8.3.1 states:
The EPSS shall be maintained to ensure to a reasonable degree that the system is capable of supplying service within the time specified for the type and for the time duration specified for the class.
Type refers to the maximum time in seconds that the load terminals shall be permitted to be without power. Class refers to the minimum time in hours the EPSS shall run without having to be refueled.
Most systems are required to be online in 10 seconds and provide power for 24 hours, but this varies with jurisdictions and application. Unfortunately, we find that EPSS installed for the protection of the bottom line, such as in telecom and data centers, receive more funding for maintenance and testing.
In recent years Underwriters Laboratories has lobbied for acceptance of its UL 2200 standard, which ostensibly adds a degree of reliability to all newly purchased generators. While it is a commendable effort, it only affects the construction of generators. It doesn't negate the need for a regularly scheduled maintenance and testing program on which continued reliabilityis founded. In fact, one potential problem with the acceptance of UL 2200 may be that some inspectors "rely on the label" rather than the stringent acceptance standards found in Chapter 7 of NFPA 110. Ironically, because EPSS are normally reliable during their youth, they are neglected during their lives, thereby guaranteeing their failure with age.
But the most common causes of generator failure, once an EPS has started up, are fuel problems, which include fuel quality, clogged filters, failed transfer pumps and lack of redundancy.
Regarding fuel quality, NFPA 110 gives some guidance. The standard states that:
18.104.22.168 Fuel system design shall provide for a supply of clean fuel to the prime mover.
22.214.171.124 Tanks shall be sized so that the fuel is (1) consumed within the storage life, or (2) provision shall be made to replace stale fuel or (3) clean fuel.
Fuel filters for critical applications should be of the double- or triple-bypass variety, where the changing of a clogged filter does not necessitate the shutdown of an EPS. An added best-practice procedure is to install dual transfer pumps to transport fuel from the main storage tank or tanks, and to have them powered by separate panels to provide some measure of redundancy. It is also good practice to provide a day tank for each EPS, rather than one day tank for multiple EPS.
Monthly testing of the EPSS should include the following NFPA 110 standards:
8.4.2 Generator sets in Level 1 and Level 2 service shall be exercised at least once monthly, for a minimum of 30 minutes, using one of the following methods:
Under operating temperature conditions and at not less than 30 percent of the EPS nameplate kW rating;
Loading that maintains the minimum exhaust gas temperatures as recommended by the manufacturer.
126.96.36.199 Diesel-powered EPS installations that do not meet the requirements of 8.4.2 shall be exercised monthly with the available EPSS load and exercised annually with supplemental loads at 25 percent of nameplate rating for 30 minutes, followed by 50 percent of nameplate rating for 30 minutes, followed by 75 percent of nameplate rating for 60 minutes, for a total of 2 continuous hours.
NFPA 110, 7.1.5 gives the owner the opportunity to either "load bank" the EPS, or to add nonessential load. It states:
When the normal power source is not available, the EPS shall be permitted to serve optional loads other than Level 1 and Level 2 system loads, provided that the EPS has adequate capacity, or automatic selective load pickup and load shedding is provided as needed to ensure adequate power to (1) the Level 1 loads, (2) the Level 2 loads, and (3) the optional loads, in that order of priority. When normal power is available, the EPS shall be permitted to be used for other purposes such as peak load shaving, internal voltage control, load relief for the utility providing normal power, or cogeneration.
Preparing for Y2K probably did more to lull us into a false sense of security than any subsequent event. Money was thrown at EPSS around the country to prepare for an event that never happened.
But during the months leading up to the 2003 Northeast blackout, monies were allocated elsewhere and EPSS failed—all over the region. Therefore the following NFPA 110 paragraphs should be followed:
8.4.8 The EPSS shall be tested for the duration of its assigned class (see Section 4.2), or for a duration agreed to by the authority having jurisdiction for at least 4 hours, at least once within every 36%%MDASSML%%48 months.
(More than likely, this paragraph will be modified in the 2005 edition of NFPA 110 to limit the run time to four hours and to limit the maximum time period between four-hour tests to 36 months.)
188.8.131.52 The load shall be the EPSS system load running at the time of the test. The test shall be initiated by opening all switches or breakers supplying normal power to the EPSS.
184.108.40.206 A power interruption to non-EPSS loads shall not be required.
Further, if the EPSS components are not located in friendly environments, as is often the case with EPS, the odds of a failure increase geometrically. This is somtimes due to the actions of humans, the weather or both.
Architects and owners should not place an EPS, circuit breaker or ATS in a location that would not be selected if the EPSS were the only source of power. The practice of allocating square footage only to "income producing processes" should be ignored when considering a home for the EPSS. For example, NFPA 110 states:
Battery heaters shall be provided to maintain battery temperature at a minimum of 50 degrees F (10 C) and shall automatically shut off when the battery temperature reaches 90 degrees F (32 C).
There is a message here: It gets cold outside, and batteries are at risk, along with the people the EPSS serves in the event of an emergency.
While NFPA 110 currently does not prohibit the placement of legally required EPSS on the outside of building, on a roof top or in a basement prone to flooding, there is a move by some to rethink this issue. For example, owners in Houston, Texas, have been educated on the principals of water not aiding the combustion process when their diesels tried to operate while immersed under 15 feet of water. And in Homestead, Fla., owners found out that it's not so much that the wind is blowing 150 mph; it's what the wind is blowing. If the generator located outside the back door gets hit with a Volvo, it will most likely quit churning electricity.
Roof tops are another curious choice for generator placement. No one forgets the experience of servicing a roof-top generator in a lightning storm. The first thing you want to do is call the architect who designed the facility to come over and assist with the job. Or what about hauling 100 gallons of motor oil to the roof? You'll also have to haul the same amount down. And then, there's the vibration problem. I should note that I've never seen a utility company place its generator on the roof.
However, one example comes to mind where a generator would have fared better on the roof. A few years ago, a disgruntled employee at a prominent hospital threw an office chair off the roof of a seven-story parking lot onto an emergency generator used for life-safety loads.
Speaking of hospitals, this raises some general issues about siting generators in a healthcare setting. A plaintiff's attorney could make a case to a sympathetic jury if a client's loved one lost his life because of a value-engineering decision to place the emergency generator in a "less valuable location."
Proper placement is a vital part of ensuring EPSS reliability. But it's not the only thing. A preventive maintenance program is essential, and this depends on constant monitoring of the system.
EPSS operating data, along with utility information, should be remotely monitored, according to NFPA 110, 220.127.116.11. There are several reliable monitoring systems available that can prove invaluable for trouble-shooting, alerting personnel to problems, providing AHJ test reports and defending oneself in a courtroom.