Fuel Advantage: Shore Power Safety

When it comes to engineering and safety standards for truck-stop electrification (TSE) systems, it’s hard to find anyone more knowledgeable than Mike Meleck, OEM account manager for Phillips & Temro Industries. Over the past several years, Meleck has worked with the Electric Power Research Institute (EPRI) to establish National Electric Code standards for truck stop wiring, he has chaired the Society of Automotive Engineers (SAE) Committee to establish the J2698 standard for the 120V AC electrification of trucks, and, as if that isn’t enough, he most recently chaired the Technology & Maintenance Council (TMC) Task Force on the establishment of Recommended Practice (RP) 437, on “Guidelines for Truck Stop Electrification Interface.”

TSE encompasses several technologies, but in general refers to systems by which trucks can hook up to 120V AC power supplies at truck stops in order to operate engine block heaters and cab HVAC systems, for the purpose of eliminating idling time. Because external 120V AC hookup systems have been in widespread use in the marine and recreational vehicles markets, they are commonly referred to as “shore power” systems.

THREE STANDARDS

They seem like simple enough systems; why then, do they require guidelines and standards from the National Electric Code, SAE and TMC? That’s where uber-chairman Meleck fits in.

“Ultimately you have three different categories here,” he says. “One would be all the wiring that’s on the truck, as set by SAE. Two would be all the wiring that’s at the truck stop and sets the infrastructure for the pedestals; this is the wiring that actually goes all the way back to the transformer. The truck stop wiring standard is set by the National Electric Code.

“The item that’s missing is the interface that goes between the truck and the infrastructure at the truck stop facility,” he says. “That interface happens to be the driver, extension cords, and any appliances that he or she may use. So, from the TMC’s point of view, the drivers’ perspective needed to be captured.

“There was a reason for this (TMC) guideline and the other guidelines related to 120V AC wiring,” Meleck explains. “The S.1 electrical group at TMC came up with RP160, which established guidelines for installation of 120V AC wiring and inverters. This RP led to standardization at SAE through J2698. The driving force behind the S.1 group RP160 was that people were putting together (shore power/inverter) systems on their own that turned out to be unsafe in several ways: incorrect wire sizes; non-regulatory-approved products; and products that weren’t suitable for a vibration environment. The new RP 437 is an extension of RP 160 to cover the interface area in-between what’s on the truck and what’s available at the truck stops. So, ultimately we’re looking to cover all areas where there’s opportunity for either electrical shock or fire.”

DOING IT RIGHT

We asked Meleck to comment on some of the significant recommendations in RP 437:

» The RP calls for specific extension cord gauge and length—12 gauge for 15 and 20 amp connections, up to 25 feet in length, and 10 gauge for lengths over 25 feet—but are the right cords commercially available to truck drivers?

Meleck says no: “What’s readily available to the driver are those things that you would buy at a Home Depot or similar kinds of stores, generally used for in-home wiring, usually an extension cord that happens to be 16 or 18 gauge wiring.” These types of cords, the RP states, are inadequate for TSE use.

“These are used for low current, temporary purposes in your house” Meleck says. “And you may also find plenty of outdoor rated extension cords that are 14 gauge, meant for 15 amp service. SAE and NEC agreed that the 20 amp current threshold would provide more benefit to operate the hotel loads on trucks. This 20 amp threshold would require a higher rated cord than what you could normally find.

“Those truck manufacturers and system suppliers who supply 20 amp systems will recognize that they should provide the extension cords that go with it,” he says. “And that’s what’s occurring with some of the products that are being released that have the 20 amp threshold.

“There’s an extension cord length setting in RP 437 of 25 feet,” he continues. “A lot of times people will use extension cords that are quite a bit longer, 100 feet or so, and what happens with increased length of wire is you get a degradation of the voltage level; the voltage drops. The voltage drop affects the performance of whatever you’re plugging into. That’s why we recommend no more than a certain length—12 gauge for up to 25 ft; 10 gauge for 25 feet or longer—It’s just to ensure that you have proper voltage available to operate whatever you need to operate.”

» The RP directs drivers to inspect their extension cords at each usage, and to position them between the truck and the power outlet in such a way that they won’t be tripped over, but can fleets depend on the drivers to do this?

“Considering the number of household fires that take place because of improperly-sized extension cords, or old extension cords that have worn out and gone past their date, I would say that some driver instruction should be done,” Meleck says. “Even though it is common sense, it is of value to discuss that you don’t use really old wire, and you make sure that your wire gauge is big enough to handle the load.”

» The RP calls for safe break-away of cords, in case the driver ever pulls away from the power stand without unplugging first, but isn’t that already the standard?

“The connector products that we’ve chosen both on the SAE side and on the truck stop side use straight blades, so that if you do pull at it, it will come apart naturally,” Meleck explains. “There was a market push to go with locking connectors, for higher amperage applications, 30 amps or higher. The breakaway provision is put in place more to cover the future direction that involves higher current applications, and to insure that as people start to get into higher amperage applications that they consider that when the driver is going to pull away he is occasionally going to forget that he’s plugged in. If the connection points are locked in place, there’s going to be damage, either to the truck or to the electrical pedestal.”

For expanded coverage on idle-reduction technology, watch for the Summer issue of Fuel Advantage, available at www.fuelpub.com

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