Carrier Air Conditioner Beat Frequency

Vibrationdata

The top image is the air conditioner mounted near a back corner of my home. It is Carrier model 24AHA424A003. It has a scroll compressor, model ZP20K6E-PFV-130. I measured its output sound using my Android Smartphone.

The condenser motor nominal speed is 800 RPM (13.3 Hz). The motor’s fan has 3 blades with a nominal blade passing frequency of 40 Hz. The 41.6 Hz spectral peak appears to be the actual blade passing frequency with the motor running about 3.8% higher than nominal.

The scroll compressor frequency is 60 Hz with a 2X harmonic at 120 Hz. The difference between the 118.6 & 120 Hz peaks is 1.4 Hz which is the audible beat frequency in the sound file. The 1.4 Hz delta pattern is repeated near 180 & 240 Hz.

Principles of Refrigeration

• Liquids absorb heat when changed from liquid to gas
• Gases give off heat when changed…

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