The Apparatus Architect: Part 25 - Designing Rescue Squad Apparatus

Tom Shand and Michael Wilbur discusses the line voltage generator system as one of the most important fixed components on any rescue vehicle.


One of the most important fixed components on any rescue vehicle is the line voltage generator system. The generator and 120-volt lighting system that is designed into the rescue truck will provide much-needed scene support on the fireground and other emergency incidents. The type of generator and...


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One of the most important fixed components on any rescue vehicle is the line voltage generator system. The generator and 120-volt lighting system that is designed into the rescue truck will provide much-needed scene support on the fireground and other emergency incidents. The type of generator and kilowatt output rating will greatly influence the overall design of the rescue truck and, depending on the make and model of generator system, may impact other operational features on your new unit.

The National Fire Protection Association (NFPA) Standard 1901 offers excellent guidance covering the design and proper installation of line voltage electrical systems; see Chapter 23 and the appendix of the standard. There is no specific requirement for the size or number of generators that should be carried on truck company or special service units. With this in mind, we will offer practical advice on what fire departments should consider when outfitting rescue or squad apparatus.

One unique aspect of rescue squad and special service units is that there is relatively little guidance with respect to what units are expected or need to carry for equipment. In some parts of the country, such as the metropolitan Washington, D.C. area, several county fire departments have detailed standards on what equipment is to be carried on rescue squad and rescue engine apparatus. Beyond this, there are some locations that have are specific equipment requirements for urban search and rescue (USAR) units and hazmat apparatus. If your department is just getting started with designing a new rescue apparatus, take the time to obtain an inventory list from another department or jurisdiction to see what type and quantity of tools and equipment should be carried.

Portable gasoline-powered generators should be carried on every special service apparatus. Smaller 500- to 2,000-watt-output units equipped with lamp heads can be used to illuminate remote areas as well as provide power for smaller electrical equipment. Consideration should be given to carrying one or two of these types of light/generator plants together with a larger-output portable generator. Midsize portable generators can provide 2,500 to 6,000 watts of power and, depending on size, can be frame mounted or provided with rubber tires. These units can be particularly useful when you need to provide a remote power supply at a scene without tying up an entire apparatus for extended periods.

Diesel generators are commonly available in sizes from six to 15 kilowatts and provide a reliable source of power; however, they weigh in the area of 500 to 900 pounds and take up a considerable amount of room within a compartment. When they are mounted on the floor of a side-body compartment, make sure that there is adequate ventilation for the unit to run; if using a larger-output unit, you will have to balance out the body with other equipment on the opposite side of the unit. Diesel generators offer the advantage of being able to produce power when the vehicle is in motion as well as running when the apparatus is shut down. These features may be beneficial to the department, depending on operating conditions at the scene of an incident.

Power take-off generators work well with rescue vehicles in that they generally do not take up outside compartment space on the apparatus. These generators come in sizes from 15 to 40 kilowatts and can be powered from one of the PTO openings on an Allison automatic transmission. Larger output generators in the 50- to 150-kilowatt range are run by transfer case gearboxes similar to a fire pump. These high-capacity units are typically used on air/light units or special service units, which operate electrically driven breathing air compressors or other high-demand components.

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