Keep Your Cool With Racked Equipment

by John Bisset

One of the problems with using vented rack panels to separate your equipment is that they are too large, eating up prime space in the rack.

Tony Lopez, chief of Clear Channel's Pueblo, Colo., cluster, writes that the smallest ventilated panels he's seen are the 1-3/4-inch models from Middle Atlantic. These are great vented panels for higher-wattage equipment; but for lower-power equipment such as mic processors, MiniDiscs, etc., a smaller spacing is adequate. Furthermore, this kind of equipment often is located in console turrets or similar small racks where vertical space is at a premium.

For small equipment racks, where even 1RU vented panels take up too much critical space, Tony came up with a solution. By cutting a half-inch from both sides of the standard 1-3/4-inch vented panel and discarding the middle section, you are able to keep the factory bend on one side. See Fig. 1.

Fig. 1: Modifying a standard vented rack panel.	Fig. 2: The smaller panel reduces the amount of vertical space.

Each standard 1RU vented panel yields two 1/2-inch vented panels that fit well between low-power equipment, but without hogging valuable vertical rack space. Fig. 2 shows the finished product.

Reach Tony at TonyLopez@clearchannel.com.

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Contributors to Workbench, please note our new e-mail address. You can write to me at jbisset@bdcast.com.

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Tim Walker has run a contract engineering business in western North Carolina and western Virginia for many years. Regarding our discussion of UPSes and how they dislike dirty generator power, Tim resolved the problem by selecting a more tolerant line sensitivity setting on his American Power Conversion UPS.

More effectively, Tim operates the UPS behind a Sola voltage regulator that not only regulates voltage, but also attenuates harmonics. At one location, Tim uses a Sola model MCR500 voltage regulator. This regulator powered two APC model SU450 UPS supplies.

Tim offers a word of caution. The voltage regulator is a hog for power itself, and generates a fair amount of heat. Still, it cleaned up the power from a Home 4500 Watt generator to the point that the UPS didn't object. He can be reached at timwalker@dilyns.com.

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Leon Amstutz is CBRTV certified and hails from Fort Wayne, Ind. He has a great deal of experience with UPS systems and generators, having served as a full-time engineer and then as a consulting engineer with missionary radio network - Radio Lumiere, Haiti - for the over three decades.

In Haiti, even the commercial electric power source (when available) regularly tends to run anywhere from 59 to 62 Hz. That fluctuation caused similar problems with the station UPS.

What Leon found is that most UPS systems are more sensitive to frequency variations than line waveform. By default, most will only tolerate about +/- 0.5 Hz deviation from 60 Hz. Generators, especially before they are fully warmed up, typically deviate as much as +/- 2 Hz, particularly if you have large loads that cycle on and off.

Most UPS brands have a field programmable configuration option or a factory PROM update for use with generators. This option or update will allow you to widen the frequency tolerance of the UPS so that the UPS doesn't continue to run after the generator starts.

Some units will also allow you to adjust the minimum and maximum voltage levels tolerated before the UPS kicks in. Leon has been able to resolve these generator compatibility problems with several different brands of UPS. Check with the manufacturer of your specific UPS to see if this option is available; it will likely solve your problem.

Leon commented on another topic in a recent column: the use of razor security wire atop tower fences to deter vandals. Leon has found that in climates where ice buildup is common, razor wire does not survive falling chunks of ice from a nearby tower or guy-wires.

The razor wire actually is a thin stainless steel strip and it is fairly brittle, unlike galvanized barbed wire. If a chunk of ice hits the razor wire and flattens it, the wire often breaks and uncurls. You are left with dangerous strips of razor wire whipping around the fence at head level.

Fig. 3: Barbed wire can be bent back into position.

At least with barbed wire, if it gets bent out of shape, as shown in Fig. 3, you can usually rebend it (carefully) back into position numerous times. In Leon's experience, barbed wire survives much longer than razor wire in northern climates.

Leon Amstutz can be reached at l.amstutz@att.net.

John Bisset has worked as a chief engineer and contract engineer for more than 30 years. He is northeast regional sales manager for Broadcast Electronics. Reach him at (571) 217-9386, or jbisset@bdcast.com.

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