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Posted by Jean on February 17, 2009, 2:41 pm
>http://www.youtube.com/watch?v=9gfnmVB5q3c&NR=1
>I have a Goodman GSZ (installed Nov) that has started making the same
>noise during defrost. There is also a neighbor with a Frigidaire that
>makes a similar noise during defrost. He had an HVAC tech come and
>tell him that is the way these things work. That was a quick 100
>bucks.
Here's an interesting comment I found on noise during defrost cycle:
"A scroll type compressor is employed in a heat pump system having a
solenoid actuated four way flow reversing valve. A processor monitors
a system parameter that is indicative that a flow reversal has taken
place or is about to take place, at which time the compressor motor is
shut down for a predetermined period of time during which the
compressor produces objectionable noise produced by separation of the
scroll element due to a low pressure differential over the compressor.
At the end of the period, the compressor motor is re energized. The
processor is arranged to cycle the compressor at the beginning and end
of each defrost cycle or when the system undergoes a change in its
operational mode."
The Lennox 34M63 has 30 second compressor delay during switchover as
well as 5 minute anti-short cycle. In addition, the high and low
pressure lockout feature is preferable to uncontrolled cycling in my
mind. The diagnostic LED's are also a nice feature.
Goodman thermostat appears to be close 28°F / open 65°F from older
install book - will have to check current part#
B1370803 DEFROST THERMOSTAT
I mentioned this to the HVAC tech and he said it was a good idea. He
said he carries these in his truck to use as replacement for defective
defrost boards.
Still awaiting his services as he is very busy.
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