by Christopher Maione
We place a lot of very expensive AV equipment in our racks, and far too often, we focus on the equipment in the front and not what is happening in the back of the rack. Power distribution, protection, and surge elimination are "back rack" items which should be given some careful thought.
First, let’s define what each of these mean:
Power Distribution: This is simply taking the AC main power for the rack and distributing it to multiple outlets (such as with a simple plug strip) in order to provide an AC outlet for all the equipment in the rack.
Protection: Protection “protects” AV/IT equipment from faults which may occur in the electrical distribution system and/or wiring. Protection includes a piece of equipment installed along the AC power lines which monitors and “protects” the AV equipment from high voltage spikes, low voltage sags, overloads, ground faults etc. Protection is sometimes also referred to as “Conditioning” as the equipment conditions and shapes the AC signal
Surge Elimination: Surge protection and elimination is designed to protect AV/IT equipment from voltage spikes which can be caused by compressors, transformers, lighting dimmer panels and (of course) lightning strikes.
Please note—these technologies do not provide any sort of Uninterrupted Power Supply (UPS), however, in many instances, power distribution and surge protection technologies are utilized in conjunction with UPS equipment.
So in the world of AV/IT, the well-known names of power management devices include:
• APC
• Furman
• Middle Atlantic
• SurgeX
• Tripp Lite
I would like to also point out that AMX is also a player in this market with their NXA-PDU-1508-8 power distribution unit (PDU). In addition to power distribution, this AMX unit also ties to their control system Resource Management Suite (RMS) for power monitoring (per outlet) and energy management functionality.
So let’s start with the simplest, power distribution, and again, this could be as simple as a multiple outlet plug strip. Power “distribution” is just that, distributing AC power to multiple outlets.
Each of these units is basically a multi outlet (eight) power distribution unit (PDU) with some sort of power conditioning, or surge protection. I’ve picked the models below from each manufactures product line which represent a basic (eight) outlet power distribution unit so we could look a little deeper into the “protection” each PDU provides.
Next, let's look at protection, conditioning and surge elimination. Here is where we begin to see competing products such as:
APC's SurgeArrest Performance
"SurgeArrest components such as MOVs and Thermal fuse ensure instantaneous reaction to lightning strikes and wiring faults. If the surge components are damaged due to power spike or over voltage, excess power cannot reach your equipment. " (apc.com)
Furman's M-8X Power Conditioner
"Noise filtration, AC noise filtering to reduce radio frequency and electromagnetic interference (RFI/EMI). Surge protection, spike and surge protection ensures equipment stays safe and your power stays clean. Please note, the Panamax description below is the same, Furman is owned by Panamax." (furman.com)
Middle Atlantic: PD Series, PD-920R
"Rackmount power distribution unit is equipped with 8 circuit breaker protected rear outlets, and one front outlet. Standard equipment includes surge and spike protection that utilize a clean line to neutral that does not pass noise contamination to ground and EMI filtering." (middleatlantic.com)
Panamax's M-8x2
"Noise Filtration: AC noise filtering to reduce radio frequency and electromagnetic interference (RFI/EMI). Surge protection—spike & surge protection ensures equipment stays safe and your power stays clean." (panamax.com)
SurgeX's SX1120RT or IPX versions
"Provides guaranteed surge protection and power conditioning for audio, video, broadcast and computer equipment. Features both common mode and normal mode.Impedance Tolerant EMI/RFI filtering, SurgeX ICE—Inrush Current Elimination and COUVS—Catastrophic Over/Under Voltage Shutdown for a complete power conditioning solution." (surgex.com)
TrippLite's Audio /Video Surge Suppressors
"Tripp Lite offers more than 3,000 products, ranging from network-grade UPS systems to cables for every application." (tripplite.com)
Tripp Lite offers premium surge and line noise protection for all audio/video components, including HDTVs and entertainment centers. There are two basic types of surges which can fry your equipment. They are officially classified as Type 1 and Type 2
Type 1: Surges commonly caused by equipment such as copiers or appliances cycling on and off, affect equipment many times during the course of the day. Over time, Type 1 surges will cause circuitry—as well as surge protectors to degrade and fail.
Type 2: Surge events typically occur during a lightning storm.
Protection
There are several technologies utilized within a power distribution unit to “protect” equipment. The most common are:
Metal Oxide Varistor (MOV)
Transient Voltage Suppression (TVS) which is also MOV-based
Gas Discharge Tube (GDT)
Transient Voltage Suppression (TVS) diode
Series Mode (SM)
Surge protectors which have MOVs between live, neutral and ground divert energy to both neutral and ground, and will contaminate both the neutral and the ground wires.
Some of the problems with MOV technologies are:
• The safety ground is the same as the equipment chassis and system ground, and surges diverted to ground will allow energy to flow in chasses and cables that join interconnected equipment.
• Dumping surge energy onto the system ground instead of blocking and containing it can result in high-voltage energy traveling along interconnecting cables and causing permanent damage to input or output stages.
Surge protectors which have MOVs only between live and neutral divert energy only to neutral and do not contaminate the ground wire, but they are also not effective at completely protecting equipment.
Gas Discharge Tube and Transient Voltage Suppression diodes are sort of like “fuses.” In a true surge event they are “sacrificed” in order to protect the equipment. While effective in stopping surges—you now need to repair or replace the protection equipment device before it will operate again.
Each of the products reviewed use one of, or a combination of, the technologies above—with the exception of SurgeX, which is the only manufacturer to use Series Mode surge suppression technology. In fact, they hold a patent on what they call Advanced Series Mode Surge Protection.
Advanced Series Mode technology is much more effective than conventional MOV circuitry or MOV-Hybrid designs and is completely non-sacrificial. This technology provides for zero let-through of surges up to 6,000 volts (unlimited surge current) without producing any ground contamination.
Christopher J. Maione, CTS-D, is principle of Christopher Maione Associates and an Adjunct Faculty member with InfoComm. Reach him at cmaione@chrismaione.com.
