IMPROVING APPARATUS ELECTRICAL SYSTEMS

IMPROVING APPARATUS ELECTRICAL SYSTEMS

BY KEN MENKE

In 1962, when I joined the fire service as a member of a small volunteer department, my company operated an engine that had been in service since 1936. Although old, Engine 2 usually ran very well. However, 33 years later, I still vividly remember responding to the call of the house siren and being unable to start the motor. Newer apparatus had dual batteries to cope with such a problem, but our old engine had only one battery and it was totally dead.

The regular driver arrived next and was not the least bit concerned. As soon as the full crew arrived, he set the ignition to the magneto position, had us push the engine onto the ramp, popped the clutch, and away we went. Arriving on the scene, we pumped a little water from the booster tank, put out the fire, and went home.

Back at quarters, the driver showed me the engine crank that was carried in the side compartment, but he insisted it was much easier to just push the rig. Our engine carried no radio, the flashing red lights could hardly be seen in daylight, the unmuffled exhaust was louder than our little siren, and the bell always worked just fine. Electrical power was convenient but in no way essential to the pumper`s operation.

That has all changed. Today, just one hiccup of the electrical system can turn your brand new pride and joy into the biggest red boat anchor in town. Ambulances have had electrical problems for years, but it was not until I experienced the total failure of a first-due engine that I recognized the need for better electrical systems on larger apparatus.

The engine that failed was supplying most of the water being applied to the fire. A second alarm for personnel had been called, but I really thought we had the fire under control. With no warning whatsoever, the water supply pumper died and would not restart. Before the incident was over, the fire went to four alarms.

In rather typical fashion, the pumper`s electrical system was overloaded and, although the department didn`t know it, the six-month-old pumper had at least one bad diode in the alternator. As the engine worked away with all the warning lights blazing, the system voltage dropped to around 10 volts, and the on-board engine computer shut down. To protect the engine and transmission from damage (and their manufacturers from warranty claims), vehicle computers are programmed to shut down before they lose their minds and do something foolish.

INCREASED DEMANDS ON ELECTRICAL SYSTEMS

After receiving a number of reports of similar problems, the National Fire Protection Association (NFPA) Technical Committee on Fire Apparatus asked its Electrical Subcommittee to investigate the problem and propose improvements to be incorporated into the standards for all fire apparatus.

In a very few years, fire apparatus had changed from gasoline engines to computer-controlled diesel power, and the electrical system needed to be brought up to date. For years, dual batteries had provided a simple fix for electrical problems on gasoline-powered apparatus, but by 1990 virtually all apparatus were diesel-powered. These high-compression engines required such large batteries to crank that dual batteries were no longer practical, and the requirement was dropped.

While engine and transmission computers and other sophisticated electronic systems were available five years ago, few fire chiefs thought they would ever be widely used on fire apparatus. They probably were correct in thinking that on low-mileage vehicles like fire engines, the small fuel savings produced by these complex systems would be less than the cost of maintaining them.

Unfortunately, the total number of engines and transmissions used in fire apparatus is very small compared with those used for over-the-road trucks. Consequently, computer-managed power trains for large trucks are designed primarily for long-haul truckers whose primary concern is fuel economy. Whether we like it or not, the fire service must use components designed to meet an entirely different set of priorities than its own.

Over-the-road trucks discharge a fraction of the battery capacity to start and then quickly recharge the battery and run for miles with a balanced electrical system. Over-the-road trucks do not have booster rewind motors or mechanical sirens and do not sit for hours at the side of the road operating warning lights that draw more than a hundred amperes.

Fire trucks have periods of enormous electrical load and traditionally have used the battery set to carry the load when the alternator can`t keep up. Unfortunately, unlike warning lights and mechanical sirens, which function to some extent over a wide range of electrical voltage, computers are finicky and will operate only in the range for which they were designed. When the vehicle batteries are driven into deep discharge, the system voltage drops and the computers shut down. Even if the engine will crank, the voltage may be so low while cranking that the computer will not permit the engine to fire.

To further complicate the problem, the soundproofing in modern automobiles is so good that sirens are much harder to hear. Tests by the Society of Automotive Engineers (SAE) have shown that a 100-watt electronic siren provides as little as 50 feet of effective warning to the driver of a typical automobile. A driver listening to music in a highly soundproofed luxury car may not even hear the siren. Sirens have become secondary warning devices. They are great for pedestrians and children on bicycles but not very effective for motorists.

To compensate for reduced siren performance, many fire departments have added warning lights. Until 10 years ago, NFPA 1901, Pumper Fire Apparatus–1991 required only a single red roof light bright enough to be seen at a distance of 500 feet. Today, typical warning lights are more than 10 times this intensity. They already are the largest electrical load on many fire trucks, and it simply is not possible to add more lights to most apparatus without overloading the system. Adding more lights usually invites disaster. Controlling this problem was the key to defining a better electrical system.

THE FIRST WARNING LIGHT DEMONSTRATION

The Electrical Subcommittee turned to the manufacturers of warning lights for help. At a meeting in Newark, Delaware, in May 1991, a program was formulated to demonstrate the performance of two systems: one used older warning lights that just met the minimum performance required under NFPA 1901. The second required about the same amount of electricity but used higher efficiency devices placed more strategically on the apparatus.

The demonstration ran during the Fire Department Instructors Conference (FDIC) in Cincinnati, Ohio, in 1992. The two systems of warning lights were mounted on identical rental trucks. Members of the NFPA 1901 Committee and guests representing a cross-section of the fire service observed the vehicles at various distances, moving and stopped, both day and night. During the demonstrations, observers completed a detailed questionnaire. Their answers indicated that the system then specified in 1901 was inadequate for day use and was barely adequate at night. They also said the new system, while better, was still not nearly good enough.

THE SECOND WARNING LIGHT DEMONSTRATION

The Electrical Subcommittee reviewed the suggestions of the observers and proposed that another demonstration be held during the 1993 FDIC. The energy allowed to run the warning light system was increased to 40 amperes–the maximum that seemed reasonable using the standard electrical system on a commercial chassis.

All U.S. manufacturers of warning lights were invited to outfit a demonstration vehicle. Four–Code 3, Federal, Tomar, and Whelen–actually did. The Cincinnati (OH) Fire Department generously provided reserve engines for the demonstration. Each manufacturer proposed a different way to improve performance, and observers judged all the systems demonstrated adequate and vastly superior to the system shown in 1992.

Once it was determined that an engineered array of warning lights could produce an effective signal using only 40 amps or less, the Electrical Subcommittee could write a performance standard that could be achieved with commercial and custom chassis.

Based on the photometric data submitted by the manufacturers for their respective systems, the Subcommittee developed a comprehensive performance standard for fire apparatus. Following the receipt of additional information on alternators, the allowance for warning lights was increased to 45 amps for pumper-sized vehicles and as much as 55 amps for vehicles the size of tillered aerials. For vehicles less than 22 feet long, the required number of lights was lowered and the electrical load reduced to 35 amps, in keeping with the smaller size of the apparatus.

NEW NFPA 1901 WARNING LIGHT

REQUIREMENTS

The new requirements for warning lights are contained in Chapter 9 of NFPA 1901. This standard divides the area around the apparatus into four zones (front, rear, right side, and left side) and two levels (upper and lower). The total energy (optical power) projected by the warning light system is specified for each zone and each level. The required optical power in each zone and level varies according to whether the warning lights are being used to call for the right of way when responding or to protect a vehicle that is stopped and blocking the right of way. For example, when responding and trying to clear traffic, the upper-level warning devices must project one million candela-seconds per minute of optical power into the front zone but only 400,000 into the rear zone.

The lesser warning to the rear makes sense because the probability that a speeding fire engine will be hit in the rear is quite small. However, when the apparatus is stopped, the potential for being rear-ended increases dramatically. To meet this need for more protection, the standard raises the optical power required for the rear to 800,000 and balances the electrical demand by reducing the front-zone requirement to only 400,000.

This kind of thinking is typical throughout the standard. We all know that it is impossible to have too much light at high noon in August; but at the same time, we also must realize that only so much electrical power is available. The 1901 Committee and Electrical Subcommittee have worked very hard to try to maximize the available electrical power by putting the maximum amount of warning into the right place at the right time.

The standard requires that every pumper have an electrical system that can provide 45 amps for warning lights but leaves it to the customer and the apparatus builder to decide how to get the job done. Whether a no-frills commercial engine or the fanciest custom pumper, each apparatus will have a base warning light system adequate to protect the vehicle. If a department has the resources to buy more lights and a bigger electrical system, additional lights can be added in any way the department wishes. Departments must understand, however, that some of those lights may have to be automatically load-managed.

The new standard recognizes that the two most common kinds of serious fire engine accidents involve apparatus hitting vehicles at intersections and vehicles plowing into stopped apparatus. A fire engine built to the new standard will project much more light to the rear of the vehicle and at the corners and less light to the front than is now typical. Overall, the higher efficiency lights and more effective device placement will give the fire department a lot more performance for its money.

On the downside, it will be more difficult to mix and match various brands of devices. Building a one-of-a-kind, dream lighting system will still be possible, but some simple calculations will have to be done to prove that the system will actually work. Most purchasers will find it easier to buy a precertified base system from a single vendor and then add additional lights and a larger electrical system to get the look they want. Until some new technology arrives to fill the traditional role of sirens, bells, and air horns, the warning lights are going to have to do most of the work.

GENERAL STANDARD REQUIREMENTS FOR THE ELECTRICAL SYSTEM

The proposed NFPA standard establishes the following general requirements for an apparatus electrical system.

The electrical system shall provide enough power to simultaneously operate all of the devices defined as essential to the mission of the apparatus. With the engine hot and at idle, and without discharging the battery set, the alternator shall be capable of operating the chassis, required warning lights, fire pump, and all other functions listed in the standard or specified by the purchaser. A fire apparatus should be able to operate for days or even weeks as long as fuel, lubricants, and operating fluids are added periodically.

The battery set shall be large enough to supply the electrical load defined above for a period of 10 minutes after a total failure of the alternator. This 10-minute interval is to permit the safe withdrawal of crews from the fire building or the transfer of the fire suppression activity to another apparatus.

The battery set shall be able to restart the engine after the 10-minute discharge period defined above. This reserve is to provide a reasonable chance that the apparatus will restart after returning to quarters before the battery set is adequately recharged.

Audible and visible alarms shall warn firefighters on, in, and near the apparatus of an impending electrical failure early enough to permit appropriate action to be taken.

The above requirements seem so basic that it is difficult to believe any fire department would accept a fire engine that did not comply. In fact, after completing the initial pump test, the batteries on a substantial number of brand new pumpers are so discharged that the apparatus cannot be restarted using its own battery set. A battery charger now is standard equipment at most test pits.

ENSURING ELECTRICAL SYSTEM RELIABILITY

Under the proposed NFPA Standard for Automotive Fire Apparatus, both the purchaser and manufacturer must do their part to ensure a reliable electrical system.

The purchaser must tell the manufacturer what electrically powered devices, in addition to those mandated by the standard, are considered essential to the mission of the apparatus.

Based on this information, the manufacturer must prepare an electrical load analysis and provide an electrical system that will provide the quantity and quality of electrical power required. In some cases, the manufacturer may have to explain to the purchaser that the electrical power needed cannot be obtained with the chassis the purchaser desires and that something must be changed to make the apparatus buildable.

Most apparatus built today have a connected load that far exceeds the downrated output of the alternator. At any time, the electrical system can be forced into failure just by turning on too many devices. To prevent this, some form of automatic load shedding will be required on all but the most basic apparatus. The essential electrical loads cannot be subject to automatic load management. Crew members, of course, can switch off any electrical system components not needed. Nonessential loads can be automatically managed in any sequence or priority the purchaser wants.

Instrumentation will be required to detect an impending electrical failure and provide warning in time for action to be taken. In the simplest form, this instrumentation will monitor voltage and sound the alarm if the system voltage drops below 11.8 volts for a period of more than 120 seconds.

The manufacturer must perform a series of tests that prove the electrical system complies with the standard and will not self-destruct when the going gets tough. The manufacturer must provide the purchaser with documentation of these tests.

In essence, the NFPA Standards Committee has recognized that computers are here to stay and are very much a part of modern firefighting. If we don`t provide the electrical diet they demand, the computers and their electronic friends are going to eat us alive on the fireground.

It is tempting to yearn for the old days when you could roll the old rig down the ramp, pop the clutch, and fight the fire. Unfortunately, the good old days are gone forever, and the return of simple electrical systems is about as likely as the return of the six-man engine and eight-man truck.

An effective array of warning lights powered by a stable electrical system is essential to the safe operation of modern fire apparatus. The best way to do this is to select and position warning lights a little more scientifically and a little less like trimming a Christmas tree.

1992: (Left) A rental truck is equipped with warning lights per NFPA 1901. (Right) Competitors work together to make fire apparatus safer.

1993: (Top) The Cincinnati (OH) Fire Department`s reserve fleet is ready to demonstrate the newest concepts in warning lights. (Left) New ideas are put on old fire engines.

(Top) 1936: Electrical power was convenient but not all that essential. (Bottom) 1995: A momentary drop in voltage can lead to catastrophic failure.

KEN MENKE is director of the Fire Service Research Institute, a nonprofit agency based in Webster Groves, Missouri, that provides assistance to fire service agencies. He is a member of the NFPA Technical Committee on Fire Apparatus. Menke has an MBA and a degree in chemical engineering and was a founder and chief engineer of Public Safety Equipment, Inc. A volunteer captain, he remains active in the fire service.