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:

AC condenser frozen dryer and piping
AC condenser frozen dryer and piping

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):

AC condenser broken fan
AC condenser broken fan

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.

AC&R Gauge set
AC&R Gauge set

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.

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3 thoughts on “I Got The Air Conditioner Blues”

  1. A good HVAC man could install pressure relays that would open the control circuit under high head pressure, and possibly also warn you with a Sensaphone or Broadcast “Fools” alarm unit, along with saving the equipment. All of our installations have “sight glasses”, low temperature lock-out relays and the aforementioned line set pressure relays. Yearly cleaning of condenser coils with a mild acid wash keeps the fins clear of seeds and dirt which keeps the compressor happy.

  2. Sight glasses don’t always tell the story. You will frequently see bubbles on start up. Someone will misinterpret that to mean something is amiss when it in fact is not. The unit has to run for a period and stabilize and even with that I take sight glass readings with a a grain of salt. I would rather know thew suction & liquid line pressures are and the outdoor ambient.

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