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The “Law of Unintended Consequences” – How a Service Part Can “Kill” the Compressor

Products Affected: Air Conditioning and Refrigeration Compressors

  • When the motor-run capacitor fails, the capacitance of the Hard-Start Kit is still connected to the compressor.
  • With the Hard-Start Kit still connected, this will allow the compressor to start and run without the motor-run capacitor.
  • The compressor was not designed to run without the motor-run capacitor, and it will overheat and lead to compressor failure.
  • It’s estimated that between 2 to 3 million motor-run capacitors fail each year in Air Conditioning and Refrigeration Systems.

There are times when the attempt to do something positive can result in something unexpected or unforeseen. The annual increase in the number of Hard-Start Kits being added to air conditioners is a perfect example. Hard-Start Kits are being installed by contractors for a variety of reasons, such as extending the life of an old compressor, reducing starting amper- age, and lowering the load on the utilities.

Utilizing a failed “open” motor-run capacitor as the basis for our “Destructive-Analysis” experiments (in conjunction with the Advanced Technology College of Daytona State College), led directly to the failure of a number of our “test” compressors. That is, once started, a compressor WILL run without a motor-run capacitor. Compressors were never meant to operate without a motor-run capacitor. The problem will occur because the Hard-Start Kit will briefly replace the failed motor-run capacitor; thereby allowing the compressor to re-start. In our experiments, we’ve seen the compressor quickly overheat, with surface temperatures reaching as high as 101ºC (Centigrade) or 213.8ºF (Fahrenheit) and refrigerant pressures as high as 700psi. While the compressor’s own internal protective devices attempt to protect the compressor, the REPEATED restarts are what destroys it.

Past and current designs have the wires from the Hard-Start Kit connected to the same motor-run capacitor terminals that are wired to the compressor. In these designs, the capacitor terminals are acting like “terminal blocks”. With the large “boost” of capacitance from the Hard-Start Kit, compressor failure WILL occur after an extended time running without the motor-run capacitor, accompanied by the repeated “hammering” the motor takes from “high-boost” over-capacitance starts.

AmRad Engineering has the solution to this issue, the NEW Patent-Pending Motor-Run Capacitor with Compressor Protector Terminal CPT™. The new design for our Turbo series capacitors has a separate terminal specifically for use with any Hard-Start Kit. This terminal is connected internally to the common terminal and will COMPLETELY separate the Hard-Start Kit from the compressor upon a motor-run capacitor failure. This will save the compressor because the Hard-Start Kit is no longer in the circuit to allow the compressor to restart.

The New Terminal design works with ALL Hard-Start Kits, including popular 3-wire Hard-Start Kits. All Turbo200® series capacitors will be available with compressor protection technology and have the Compressor Protector Terminal CPT™. All AmRad motor-run capacitors will be available with this CPT™ terminal later.

Installation is simple. With the orange colored Compressor Protector Terminal CPT™ clearly marked and ready to install with any Hard-Start Kit/BOOSTER System. Simply attach one wire from the Hard-Start Kit to the CPT™, the other wire to the “Herm.”

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