York H 1 RA 018 S 06 - Loud knocking in wall when AC turns on
Posted 24 July 2011 - 01:58 PM
Note, the unit is approx 11 years old.
Thanks in advance for you help.
Posted 24 July 2011 - 06:03 PM
Over the years that liquid line (3/8 diameter copper line) has expanded and contracted and flexed many times. That line is now touching a piece of wood in your home. As the pipe heats up it will expand(it is copper and will always expand when heated). As it expands it jerks forward making a sound that may sound like knocking. Once the pipe is done expanding (after 30 seconds or so) it will cease to make a noise. If you paid very close attention you may hear pops/ knocks or creaks after the system shuts down, due to the pipe returning to it's original size.
I can offer no other possible reason for your noise.........besides the noise and temperature change is upsetting the rat that is living in your wall right next to your bedroom.
Posted 25 July 2011 - 01:20 AM
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