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-   -   CPH - Compressor Cycle Rate (http://www.diychatroom.com/f17/cph-compressor-cycle-rate-96860/)

OscarNelsen 02-28-2011 08:03 PM

CPH - Compressor Cycle Rate
 
I understand that setting the thermostat CPH to 3, yields 3 10 minute on/10 minute off cycles per hour.
My heat pump has a 2 stage compressor and the thermostat has CPH control for both stages. Why would you set Stage 1 to a different CPH from the Stage 2 compressor?

hvactech126 02-28-2011 08:34 PM

you would not.... both should be cph of 3

OscarNelsen 02-28-2011 10:05 PM

Thanks for your response. I have no intention of changing these settings, but want to learn. I have installed a couple of programmables, but never on a 2 stage system. Why are there separate CPH controls for the compressor stages?

beenthere 03-01-2011 05:29 AM

Quote:

Originally Posted by OscarNelsen (Post 600053)
Thanks for your response. I have no intention of changing these settings, but want to learn. I have installed a couple of programmables, but never on a 2 stage system. Why are there separate CPH controls for the compressor stages?

Because it changes how tight the temp control is. Some people like the system to shut off even at higher outdoor temps. Some people prefer the greater comfort of a unit that is running longer during the mid to 80% of design condition temp days of the summer.

A CPH setting of 3 doesn't mean it will run 3 10 minute on 10 minute off cycles per hour all the time. That is just what it will attemp and is only accurate at 50% load.

OscarNelsen 03-01-2011 09:01 AM

Thanks. I realize that what I am learnig most is the less I know.

beenthere 03-01-2011 04:25 PM

We all learn that there is always more to learn.


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