Stay Safe Around AC Disconnects
     

Greg Muir commented on Steve Franco’s submission in May showing burned breaker-panel wiring.
 
Greg is chief engineer of STARadio Corp. in Great Falls, Mont. He’s an electrical specialist who works with many insurance companies.
 
Fig. 1: Black & Decker makes the TLD-100 infrared thermometer, with a street price under $30. Use a tool like this to check temperatures of surfaces you can’t touch.
His first advice to the “do it yourselfer” station engineer: Remember that Allen head set screws are hot when they’re holding conductors to the breaker. Unless you have a fuse box or disconnect switch prior to the breaker panel, be careful. We don’t want crispy engineers here.
 
Second, in Greg’s private practice, he has one client whose insurance carrier actually requires a periodic temperature measurement of connections in breaker panels and fuse boxes as a precaution against fires.
 
This process is easy using an infrared point-and-shoot temperature meter commonly available at reasonable cost. Greg carries one in his briefcase and makes it a habit to perform checks on panel connections at least once a year, recording the results on a piece of paper inside the panel. A hot connection will jump out at you given consistent temperatures in an evenly loaded three-phase system.
 
The expense of a burned-out, high-amperage breaker is still significant but a lot less than that of a smoldering building followed by a peeved insurance carrier. Given the cost of infrared temperature meters, why not? The examination also is a value-added service that can provide revenue from your contract clients. Group stations would be wise to cycle a temperature meter around through all the stations in the chain, to catch problems before they turn into major fire disasters.
 
Visit our links page at http://radioworld.com/July-04-2012 to find some popular infrared temperature meters.
 
Greg also weighed in on our duct tape discussion. He writes that there is another product available that he finds far superior to duct tape for general applications. It is made by Scotch: Series 2000 Electrician’s Bundling Tape.
 
Greg found 150-foot-long rolls of 2-inch-wide tape at the local Home Depot. The tape has a fairly low tear resistance but is non-fabric and sports a low adhesive residue. It does not dry out in a matter of months like duct tape can and is far cheaper than many available gaffer’s tapes.

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Fig 2: A volt pen, indicating the presence of AC voltage, is a ‘must-have’ for your transmitter site.
Next time you visit your local hardware or electrical supplies store, pick up a voltage detector.
 
As seen in Fig. 2, this simple “volt pen” senses the AC electric field around a live wire. Broadcast Engineer Paul Sagi in Malaysia found one that beeps at about 3 Hz. The “business” end flashes bright red when it senses a wire with 90 to 1k VAC.
 
Some models have a push button to operate the built-in LED flashlight, useful when working on an electrical panel in the dark or poor lighting.
 
A voltage detector is a good piece of safety gear. You should never assume that power is off, even when a circuit breaker is switched to the “off” position. In rare cases a breaker can suffer a mechanical failure or contacts welded closed. Or perhaps a situation develops in which power feeds back through some other wiring and equipment.

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From retired Cox Radio Richmond Engineering Manager Jon Bennett comes an interesting report about the failure of the largest tower east of the Mississippi due to ice loads. Find the link at http://radioworld.com/July-04-2012.
  
The television station that owned the tower prepared the documentary.

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Ira Wilner, chief engineer of Monadnock Radio Group/Saga Communications Inc., has a tip following up on our little primer about mirrored meter scales in the June 6 issue.
 
Add clear labels made with a P-Touch or similar labeler, to indicate which slug/meter range is used on your power meter. With all that stations engineers must handle, it’s difficult to remember which slug is used in which line section. Identifying the meter scale will save you from grabbing a stepladder and crawling into the ceiling to read the slug in the line section.
 
For a variety of labeling machines, again see http://radioworld.com/July-04-2012.
 
Contribute to Workbench. You’ll help your fellow engineers and qualify for SBE recertification credit. Send Workbench tips to johnpbisset@gmail.com. Fax to (603) 472-4944.
  
John Bisset has spent 43 years in the broadcasting industry, and is still learning. He is SBE certified and is a past recipient of the SBE’s Educator of the Year Award. He recently joined Elenos USA, an FM transmitter company based in Miami.

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