Tales of disaster – Page 11 – Engineering Radio

I Got The Air Conditioner Blues

Back in the day, when tube transmitters ruled the broadcast world, the common practice was to have a big cooling fan moving outside air through the transmitter building connected to a thermostat. Temperature swings of 30 to 40 degrees were common, however, the tube rigs could handle almost any temperature that didn’t melt plastic or freeze water.

Today’s solid-state transmitters are not that rugged. They like to have their rooms around 70 degrees +/- 10 degrees or so. Not to mention the other computer-controlled equipment commonly found at a transmitter site. Things like air chain processors, STLs, remote controls, etc. So, lots of air conditioning is the norm, and with lots of air conditioning comes lots of maintenance.

Air handler air filters need to be checked and replaced often. Condenser coils seem to attract every type of flying debris on the planet and need to be cleaned once, possibly twice per year depending on tree and weed species near the site. Even with preventative maintenance, occasionally things like this happen:

Of course, the entire cooling coil inside is frozen solid.

This condenser is low on refrigerant, causing icing problems. It has a slow leak somewhere and is about to be replaced. Other reasons for this happening are malfunctioning or non-existent low ambient kit on the condenser fan. Sometimes less than knowledgeable persons will install a 5-ton unit designed to run throughout the year but not take into account the effect of moving below-freezing air at high speed across the coils. Insufficient air moving across the cooling coil will also cause this. Insufficient airflow can be due to plugged air filters or clogged fan/blower blades.

This one is even better (same condenser unit):

The fan blade is sheared off and jammed into the condenser coil. This happened during power transfer from generator power to commercial power. Naturally, it was at 1 a.m. in the morning after a pole-mounted transformer had been replaced. When the building transferred back to commercial power, I went outside to use the “bathroom” before my two-hour drive back home. I thought I smelled something hot, you know that cooked paint/plastic smell, but couldn’t really track it down… the winds were kicking up and another thunderstorm was on the way.

The next afternoon, however, when the sun was up and the site was working on one air conditioner, the temperature alarm went off. Upon arrival, I found the condenser breaker tripped, resetting it caused the building lights to dim. The fan motor was shorted to the case. I would theorize the aluminum fan blade suffered from metal fatigue, likely because the blades were not balanced causing a vibration. When the power transfer occurred, there was just the right combination of torque and centripetal force to cause the blade to rip, and then lodge in the condenser coil.

The fan motor has been replaced, but I think it is time to replace the whole condenser unit, which will be expensive.

I found having a set of gauges to check the head pressure and suction is a good diagnostic tool to quickly pinpoint problems with HVAC units. This way, when the HVAC tech shows up, you can quickly point him in the right direction.

The breaker keeps tripping…

This is yet another addition of the “Burned up Sh*t” collection:

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.

Crown D75 monitor amp goes terminal

Happened the other day, took out the monitor speakers too. I am not sure how this happened, but the production director reported that the speakers began making very loud squeals. Somebody finally thought to turn off the amp using the conveniently located on/off switch on the front panel.

Crown D75 audio board burned open resistor

The two-watt resistor is burned open. Also, this got so hot it burned a hole in the circuit board below it. Truth be told, I think this amp was about 25 years old and due to be replaced when the new studios were built out.

I’ve seen these Crown amplifiers self-destruct in the past.

The Devil is in the details

Sometimes it is the seemly small insignificant detail that will take a station off the air. To expound on that a bit, I have my own story which happened yesterday. The back story is this: About three years ago, some unauthorized tower climbers climbed the WICC south tower all the way to the top. The station remained on the air at full power while this was going on. Once at the top of the three hundred-foot tower, the climber, we can call him “Crack Head,” managed to loosen, then remove the beacon and throw it to the ground. Mind you, this guy had no safety climbing equipment whatsoever and he had to stand on the top plate, which is all 20″ x 20″ square, of which the beacon takes up 16 inches. A two-inch purchase between himself and eternity demonstrates that God does indeed smile on fools and drunks.

WICC south tower with long island sound in background — WICC South tower with Long Island sound in the background

Fortunately, his friend on the ground had a video camera and filmed the entire episode. Even better, they then posted it on Youtube. The police took interest in this video and its owners because the damage to the radio station was significant, and with the tower being about a mile away from the end of the Stratford Airport runway 17, presented a real hazard to air navigation. Needless to say, the video was used by the prosecution and both crackheads are now in prison, God having limits after all.

A spare beacon was hoisted to the top of the tower and placed in service. This beacon was quite old and leaky and continually failed, burning out the tower light flasher. Thus, it was time to replace it. We took advantage of the outstanding weather and the crew from Northeast Towers made quick work of it. Removing and lowering the old beacon to the ground, then hoisting the new beacon up and installing it. I goobered it by not taking pictures of the beacon fixtures flying up and down the tower. I took the station off the air for about five minutes to check the condition of the wiring going up the tower, making sure there were no shorts up the tower or back toward the transmitter building. While I was doing this, I overheard the two-way radio conversation between the tower climber and the ground crew on wiring. It seems the old beacon had only two wires, hot and neutral. The new beacon had three wires, hot, neutral, and ground. Tie the neutral and ground wires together, instructed the tower boss.

Nothing more was thought of that, it sounded okay to me. Unfortunately, the tower had other ideas. About an hour after we secured from the job and drove away, the station went off the air. It seems the neutral wire was not referenced to the tower previously. Because now the neutral wire was tied to the top of the tower, the RF found a path to the ground via the tower lighting choke at the base of the tower. It started arcing to its access door causing the transmitter to go off around 4 PM. Equally unfortunate was the fact that the construction gate was closed and I had to get a boat ride with the harbor master, which took about an hour to arrange. The entire situation was further complicated by darkness, which comes predictably around 6:30 PM this time of year.

When I arrived back out at the base of the tower, I took the metal access door off of the tower light choke cabinet. I could see the fresh track marks all across the bottom of the door. With the door off, I turned the transmitter on. Worked just fine. I tried cleaning it off with a Scotch Bright, but to no avail, the transmitter would not run at any power level with the door in place.

Finally, the harbor master becoming impatient and darkness quickly falling, I taped a garbage bag over the tower light choke box with the door off and turned the transmitter back on. The tower crew will have to come back and remove the ground wire on the beacon.

The first rule of troubleshooting: Check the last thing that was worked on first.

Update: And look, here is the original story in Radio World: Tough times a Pleasure Beach.