Former contract engineer Bob Hughes writes that after reading some of the more recent Workbench columns, he’s become even more aware of the need for “backup.”
(click thumbnail)Fig. 1: A UPS can be used to keep pumps working.
In light of concerns over transmitter site vandalism and various ways to secure those areas, he started thinking about buildings that house transmission equipment that are subject to water damage from various and sundry sources, i.e., water seepage at the foundation level, broken pipes, power failure, etc.
For years he has lived with a situation at home that has a potential for disaster. A side entrance to his basement has a sump well at the bottom of the stairs. In the event of heavy rains, the pump could fail to do its job. Over the years Bob has experienced many storms that have given the pump a workout. This is fine as long as the power is still on. But lightning strikes can take out a feeder in a heartbeat.
Bob’s dilemma: “What if no one is home to start the portable generator to supply power to the sump pump?”
Fortunately, the times that he has lost power in a heavy downpour have been few, and someone was there to connect the generator. Still, there was that nagging fear that one day, luck would run out. So in lieu of backfilling the basement entrance, Bob set out on a quest to find a cure.
Many hardware stores had sump pump battery backup devices; but the pump is a separate unit from the main device and most sump wells will not accommodate both the main unit and a DC powered backup.
(click thumbnail)Fig. 2: This AC outlet provides UPS or generator feeds.
Enter the world of the UPS. Bob contacted APC and asked for their advice. They had a model, the Smart UPS 1500, that would accommodate Bob’s pump with some headroom to spare. The pump is a Flo-Tec, 1/3 HP, and approximately 9 amps at 120 volts.
Bob contacted Flo-Tec and got their concurrence on the viability of using this particular model. The UPS was rather expensive, around $500; but the peace of mind is priceless. Fig. 1 shows the APC unit, Fig. 2 the outlet wiring.
Translating this into a commercial situation could save a facility thousands of dollars in damaged equipment and station “down time.” By the way, when you make a proactive effort to reduce risk like this, contact your insurance company. In the case of surge suppressors, I’ve had companies reimburse all or a part of the cost, which the insurer may see as a small cost to avoid a damage claim. At the least, they should reduce your premium; it’s kind of like installing a burglar alarm on your car.
However it turns out, inform your manager and owner of the steps you took to protect his or her investment.
Bob Hughes can be reached as “roberthughes” at Cox (cox.net).
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Summertime projects often keep engineers in high gear. In many cases, warm weather means more time at transmitter sites.
As you inventory spare parts, fuses and bulbs for the trouble lamp, also check on any containers of chemicals stored in the transmitter building or storage shed. Stephen Poole chiefs the Crawford cluster of stations in Birmingham, Ala.; he offers a tip from the “Be-Careful-Where-You-Store-Stuff” department.
A couple of years ago, Stephen bought a bottle of CLR calcium, lime and rust remover and stored it at one of his AM sites. He’d planned to use it to clean the toilet there, but one thing led to another – it was never a high-priority item – and it never got done. The CLR just sat in the storage room in the new building.
Over time, on trips to the site, Stephen noticed that the copper and aluminum in that storeroom began to look terrible. The aluminum had white oxide powder all over it; the copper was turning green.
He didn’t make the connection, figuring it was just Alabama’s legendarily high humidity at work. The transmitter site air conditioner has an economizer on it, after all, that opens a vent and pulls in outside air whenever the temperature is below 60 degrees. Alabama air stays humid well below that temperature.
Finally, the air conditioner stopped working. Stephen called a technician who inspected it and said that all it needed was a good cleaning deep inside; everything had become corroded.
How, Stephen wondered? He started investigating and found that the bottle of CLR was emitting fumes that caused the corrosion. He disposed of the bottle; and so far, no recurrence. Watch where you store those corrosive chemicals.
This is a suitable time to inventory old containers of chemicals at the transmitter site. Dispose properly of any that aren’t used. Those that you keep, make sure they are labeled and stored correctly.
Thanks, Stephen, for the safety tip. Stephen Poole can be reached as “spoole” at Crawford Broadcasting (crawfordbroadcasting.com).
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Summertime weather also means many of us get our share of thunderstorms.
Like all transmitter manufacturers, Stuart Peters, who heads BE’s Field Service Department, gets a fair share of lightning-related questions this time of year. I spoke with Stuart about ways to minimize transmitter damage due to lightning.
His reply stunned me: All too many transmitters are installed with little or no grounding.
In an AM application, if the spark gap balls at the base of the tower aren’t properly set, or there’s a damaged static drain choke, the lightning won’t be shunted to ground. Instead it may travel up the transmission line and into the transmitter. Once at the transmitter, if there’s inadequate grounding – copper brazed to the station ground or ground rod – the energy will find ground through components or PC boards. Massive destruction can occur.
Nowadays, most transmitters are so simple to install, little things like brazing the ground strap from the transmitter to the station ground can be put off, even forgotten. Some manufacturers provide ferrite cores or other suppression devices to be installed with the transmitter.
I inspected a station once where the ground strap was brazed to the transmitter and disappeared into a trough in the floor. The trough was covered by a piece of steel. Lifting the steel, I saw that the copper strap just lay there, connected to nothing.
The engineer explained he had been told that the pressure of the steel trough cover plate on the copper strap was a sufficient ground, because the trough was in the ground!
Check little things like this. In a new acquisition, yank on the copper to make sure it’s properly connected. Trace the strap to see where it goes. Make sure ground is ground.
In an effort to reduce exposure to lightning claims, insurance companies are now hiring broadcast consultants or contract engineers to investigate claims for them. Forget getting paid on a claim if the equipment wasn’t properly grounded. An insurance adjustor may not know the difference; but when an engineer familiar with good engineering practice inspects the site, it’s another story.
Submissions for this column are encouraged, and qualify for SBE recertification credit.