Everywhere present and visible only on Fluke meters and their kin, the electric power that courses through the audio/video, lighting, communications, and power management systems in today’s homes is the most essential, mysterious, and potentially dangerous element of household technology.
As a custom electronics dealer or installer, you owe it to your customers to offer safe, reliable power components that are properly installed. Its simply not worth risking their health and your livelihood with components that could turn into a liability.
Fortunately, well-established institutions are available to help you do this, but no system is perfect. That’s where your judgment and expertise come into play, especially when using products that manage, condition, and back-up utility-provided power.
In general, a safe product is well-designed and UL-listed. Founded in the aftermath of the fire-plagued 1893 Chicago World’s Fair, Underwriters Laboratories (UL) is the single most important protector of American homes, and your best ally in working safely. Based in Northbrook, Illinois, the labs sample nearly all electrical products sold in the U.S., including audio, video, and power components. Immense in size and resources, UL conducts more than 100,000 evaluations a year, and works with more than 65,000 manufacturers. The labs test products for fire and radiation safety, their ability to withstand stress and mechanical shocks, and more. UL even tests components within products, such as capacitors and transformers.
Even with all of this coverage, you shouldn’t automatically assume that the power protection equipment you sell, install, or use carries UL approval, or is UL-listed to the correct standard, especially as there are thousands of UL categories. For example, traditional surge and outlet strips, known as Relocatable Power Taps (RPTs), are only UL-listed for wall extensions with reactive components, such as Transient Voltage Surge Suppressors (TVSS).
The UL-listed mark is legally required in the U.S. by the National Electrical Code (NEC), and the Code of Federal Regulations (CFR), which requires it for all equipment that uses electricity in a facility. This also allows the Occupational Safety & Health Administration (OSHA) to shut down a place if it finds unlisted electrical equipment.
The broader National Electrical Code includes homes, and requires all equipment connected to the electric supply grid to be listed by UL or one of the nation’s 17 other Nationally Recognized Testing Laboratories (NRTLs). Local inspectors typically enforce NEC regulations, and can condemn or shut down any dwelling or business not in line with the NEC, given the potential for shock hazards or fire.
In reality, OSHA and local inspectors rarely check home electronics for UL-listed marks. Regulators largely rely on the market to police itself. While this usually works well, it puts the burden on dealers and especially custom installers to make sure that their products are used safely. In our lawsuit-happy society, potential liabilities can easily extend to dealers and installers.
For a variety of reasons, not all products carry the UL mark. Dealing with UL is cumbersome and time consuming, and designing for it often pushes up development costs. For many products, working with UL also extends the time to market, especially because UL is focused on safety issues, not market deadlines, competitiveness, or profit margins. Designing for the UL mark also raises a surprising number of issues, even conflicts, between design engineers seeking to push the performance envelope and those solely concerned with safety.
One result, for example, is that not all Uninterruptible Power Supply (UPS) and other line conditioning devices, especially for the high-performance audio/video market, are UL-listed, even though UPS devices and power conditioners have become standard elements in custom-installed entertainment systems, especially home theaters.
The issue is rarely the extra cost of meeting UL standards, which is negligible, but that UL standards sometimes create performance limitations that manufacturers do not want or feel that they can design around. As a responsible dealer or installer, you’ll always want to check for the UL listing. The only place the mark is required is directly on the product; it’s not required on the box or the manual.
It’s important to note that even UL-Listed products can have flaws. A classic example is the 15-Amp rating that appears on many products provided with a 15-Amp plug. This violates the UL standard and the NEC, which specifies a product can only be rated at 80 percent of the plug attached to it.
An exception is made for RPTs, which extend the full ratings of wall outlets to simple outlet strips, surge protector strips, and passive noise filters that do not consume electricity. However, some products listed as RPTs also include power conditioners, meaning devices that provide voltage regulation as well as surge protection and noise filtering. They extend wall circuits at full value, while consuming large amounts of electricity. This violates the spirit of the RPT standard and may create hazardous conditions.
Taken at face value, such “specsmanship” can also mislead installers and customers alike, and lead to hazardous conditions, like overloaded IEC-style appliance inlets and power cords. Firefighters have identified the latter as a leading cause of household electrical fires, because overloaded cords often ignite rugs, wood floors, sheet rock walls, and other interior surfaces. Installers need to pay attention not just to the presence of a UL listing, but to its proper use.
In most locations, one circuit breaker is used to protect multiple wall receptacles. A 20-amp circuit breaker can handle 22 amps continuously before tripping, even 26 amps for an hour or so. But allowing circuits to constantly experience such heavy loading can damage wires hidden inside walls and, in the long term, cause a fire. By the same token, constantly tripping a circuit breaker can cause it to weld shut, in which case there would be no protection at all. This is also a sure recipe for fire.
The NEC handles this by limiting the power draw of cord-connected devices, requiring a 20 percent de-rating as a long-term safety margin. For safety’s sake, installers should make sure power conditioners approved as RPTs for 20-amp circuits have 12AWG power cords.
There are other ways installers or consumers can inadvertently overload a 15-amp branch circuit. Many A/V products, for example, have 15-amp, IEC-style input connectors designed to accommodate 15-amp cord-and-plug sets, yet use hospital-grade, 20-amp outputs. This allows someone to plug a product rated for 16 amps into a device whose input is designed to handle 15. More important, the wall wiring feeding it is also only designed for 15 amps. Products rated for 16 amps will draw a sustained overload through the device and the branch wiring, creating a sure recipe for fire.
This is extremely dangerous, and would be forbidden if discovered by an electrical inspector or someone from the Consumer Product Safety Commission. Installers can avoid exposing clients to these ticking time bombs by following the common sense rule which says you can’t get more out of a device than you put into it. While the arrangement allows maximum flexibility, the extra flexibility is hardly worth risking a fire loss claim for hundreds of thousands of dollars.
All of which illustrates how the UL listing is an installer’s best friend, and even more so for those who understand its nuances and the limits of its reach.
Steve Williams is staff regulatory engineer for American Power Conversion.