This is yet another addition of the “Burned up Sh*t” collection:
GE 30 Amp 3 pole breaker
It is a breaker from a 5-ton AC compressor. Back in the bad old days when I was the Director of Engineering for a 28-station group Headquartered in Harrisburg, PA, I received a phone call from one of the local engineers. He stated that the studio AC unit compressor had burned out again and the breaker kept tripping. What did I think, asked him. I thought perhaps he should dig a little deeper and determine why the breaker was tripping before throwing another AC compressor at it. When are you coming to town again, he cheerfully inquired.
Okay, I get it.
I started by calling the HVAC company to inquire what had gone wrong with the compressors. Winding shorted to the case for both units was the answer received. It being July and mighty hot out, the various worker bees in the studio were feeling inconvenienced by the sweat in their eyes and dripping on their work, etc. I called the local manager and asked for a hotel room, I’d be up tomorrow. Then I called the HVAC guy back and asked in to meet me at the studio tomorrow afternoon.
Upon arrival the next morning, I found the fifth-floor studios to be hot, as reported. I trip to the roof location proved to be hotter still. I tested the voltages at the compressor unit with a DVM and everything looked good. A trip down to the utility room found the electrical panel in reasonable shape. Then the local engineering guy chimed in, “Oh yeah, I forgot to tell you, the breaker hums and gets hot when the compressor is on.”
It’s always that little bit of missing information…
I took the breaker out and sure enough, the fingers were all arched and nasty-looking.
I replaced the breaker, the HVAC guy showed up, with a new compressor and the studios began to cool off around 3 p.m.
Since then, I have specified Square D QO bolt-on breakers for new installations, especially for heavy loads like AC units, transmitters, and so on. They are a little more expensive, but in light of two AC compressors, the unscheduled trip out of town, and the grumbling staff, it is better to pay upfront for better equipment than to put up with preventable outages.
File under some new every day. Yesterday, there was an area-wide power outage in Woodstock, NY. The backup generator failed to start, however, WDST remained on the air until the UPS batteries ran out several hours later. Then my cellphone rang. Alas, yet another Sunday on the job.
Upon arrival, I found the power had just come back on, so the DJ (yes, there was a live person in the studio, on Sunday) was restarting the NextGen system and getting the station back on the air. I restarted the rest of the servers, streaming computers, and whatnot. While I was there, I figured I might as well see why the generator didn’t run.
Pressing the start switch led to the “click, click, click, click…” which normally indicates the battery is dead. Deciding that I should dig a little deeper, I got the volt meter out. Battery voltage, no load 13.8 volts. A normal reading. Flick the starter switch and measure the battery voltage again, under load 13.7 volts. Hmmmm, now that is not what I suspected. If the battery were bad, the voltage should drop down under load.
Cracked Battery Terminal
I grabbed the negative cable and it came off in my hand. Another one of those “ah ha!” moments. Upon closer examination, the terminal connector is cracked in half.
Cracked Battery Terminal
I went to the local Ford dealership and bought a heavy-duty truck battery cable. Since the battery itself is six years old, I decided to bring it and have it checked, and sure enough, the battery was going bad too. Rather than suffer through another power outage without a generator, I went ahead and replaced the battery.
Why the terminal cracked in half in the first place, I don’t know. Perhaps it was over-tightened, or some type of manufacturing defect.
Broadcasters historically have tried to remain on the air during emergency events like major storms, earthquakes, and other forces of nature. Oftentimes, commercial power is interrupted, and thus, the backup power generator is installed. Propane-powered generators for medium duty (power up to 45 KW) are popular because of the decreased environmental hazards, availability and expense of fuel, and ease of maintenance and repair. This sized generator can run the critical loads of a studio facility or a transmitter site with TPOs between 5 and 10 KW.
Katolight 45 KW generator w/outside housing
Most propane generators use a gasoline engine modified to use propane. These generators can also use natural gas, however, because natural gas has slightly less energy, the generator’s service rating is reduced by about 10 percent.
Ford inline 6 cylinder engine
The biggest error I consistently see with propane generators is improper fuel tank sizing. It might seem just fine to plop a 500-gallon tank down next to a 45 KW generator and expect everything to be just fine. 500 Gallons may sound like a lot of fuel, but the more important consideration is tank vaporization, that is to say, how fast the liquid propane can be removed from the tank for use. Propane fuel companies should be able to size these things correctly, most of them have books and charts that tell what capacities and sizes are needed. However, as a general troubleshoot guide, the following information is provided:
Generator manufacturers will specify how many BTU per hour a generator will require under full load. If not, these are some conservative rules of thumb:
For every 1 KW of electrical generation, 2 horsepower of the engine is needed*
Under full load, each horsepower will consume 10,000 BTU per hour*
Propane has 92,000 BTU per gallon
Propane weighs 4.2 pounds per gallon
*Note: These are not the figures you will find in your engineering handbooks, they are adjusted for generator winding and engine efficiency.
Propane Tank Vaporization Rates (Continuous BTU/hr vs volume at tank temperature):
Size propane in a tank (assumes 1/3 full)
Maximum continuous BTU/hr at degrees F
0°
20°
40°
60°
70°
120
129,600
188,640
247,680
308,160
338,400
150
146,880
213,790
280,700
349,200
383,520
250
253,800
369,400
485,000
603,480
662,700
325
321,300
467,670
614,000
763,900
838,900
500
396,270
567,700
757,300
942,240
1,034,700
1000
708,480
1,031,230
1,353,980
1,684,600
1,849,900
1450
816,120
1,253,400
1,645,690
2,047,550
2,248,480
Note: Tank vaporization depends on fuel level, tank temperature, and withdrawal rate. The above chart is a conservative generalization and represents a safe median value.
If a propane tank cannot vaporize fuel fast enough, the generator will begin to run lean, eventually overheat, and shut down. The vaporization rate depends on the tank temperature, which drops as fuel is withdrawn. For the above-cited 45 KW generator called to duty after a severe winter storm, the tank would need to vaporize: 45KW x 2 HP = 90 HP. 90 HP x 10,000 BTU/hr = 900,000 btu/hr. A 500-gallon tank is too small for that size generator.
As the tank temperature drops a propane tank can develop frost on the outside of the tank, even on a hot summer day, which compounds the problem.
The correct size tank for a 45 KW generator is 1000 gallons. This can also be two five-hundred-gallon tanks connected in parallel via a high-pressure line.
45 KW propane generator with two 500-gallon tanks
Also note, the generator’s radiator is facing the tanks so that when the unit is running, hot air is blowing on the tanks, warming them up. This particular generator is about 25 years old, which is why it looks a little worn. It still carries the load and mechanically is in sound condition.
Most propane fuel systems have two regulators; one high-pressure regulator on the tank, which takes the variable tank pressure and steps it down to about 10 PSI, and the vaporizer which steps the pressure down to a few ounces per square inch (or inches of water column) and adds air creating propane gas for the generator to burn.
High-pressure propane tank regulator
It is important that the vaporizer be mounted above the snow line and that there is a little screen on the air intake, otherwise, mud wasps will build a nest in the air intake and the next time the generator is required to run, it won’t start.
Low-pressure propane regulator/vaporizer
Fuel piping is also a concern, if the low-pressure lines are not large enough to handle the required BTU, the generator will run lean, creating the same problems as an improperly sized tank. Different piping has different capacities, see the following charts:
The tower climbing video that has gone nearly viral pointed out a few things. Climbing towers is a dangerous business, best left to those who are trained for it and have the insurance.
It is true that tower climbing contractors have the responsibility to protect their own workers while working on a client’s tower. That does not completely absolve the tower owner from liability. It is incumbent on the tower owner to provide a safe structure to climb. This can mean the mechanical integrity of the tower, reduction of transmitter power while workers are in high RF energy fields, and providing the proper permanently attached safety equipment on the tower itself; Climbing ladders, ladder safety cages, rungs, elevators, and fall arresting gear.
In that tower video post, I mentioned something called a safety climb. That is a cable, usually 3/8 inch stainless steel aircraft cable, attached, about eight inches from the climbing surface like this:
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The tower itself was built in 1959 and did not have this equipment when new. This was a retro fit kit, installed in 2003, I believe.
The tower climber wears a harness with a special karabiner attached to the front and waist level. When climbing this ladder, the karabiner slides up the cable. If he were to fall, the karabiner has an auto-locking or braking mechanism that would stop his fall.
Tower safety climb, attached to climbing ladder
Many tower climbers, especially those that have been in the business for a while, do not like these things. When climbing, especially if one has long legs, the tendency is to bump your knees on the bottom of the next ladder rung. This is because the belt holds the climber’s waist making it difficult to get the rear end out, away from the ladder the way most people like to climb. The alternative is to climb with the knees spread apart, like a frog, which is hard on the hamstrings and quite literally, a pain in the ass. However, if a tower is so equipped, it must be used.
I have, wherever possible, retrofitted towers with these devices. Of course, all new towers come equipped with them. In some situations, it is not possible to retrofit towers with safety climbs, either because there is no attachment point at the top of the tower that meets the OHSA spec, there is not a climbing ladder, or it would affect the tower tuning, as in an AM tower or near a TV or FM antenna.
Hundreds of gallons of ink have been spilled by Los Federals in OHSA regulations 29 CFR 1926 and 29 CFR 1910.268(g) regarding fall protection and fall protection equipment for telecommunications workers. In this litigious world, we live in, tower owners and or their on-site representatives should know these rules and make sure they are followed.
