[Bldg-sim] Difference between between a Single Speed DX and Twospeed DX cooling coil

Nick Caton ncaton at smithboucher.com
Tue Oct 19 07:44:11 PDT 2010

Hi Deepak,


I think you mean single vs. two-speed DX compressors.


Having either two-speed compressors or multiple compressors for a given
DX coil means effectively you have two or more stages of cooling.
Staged cooling means you don't need to run the compressors full-out for
short periods when you only have a partial cooling load during the year.
As a result, they don't have to cycle on and off as much.  Cycling on
and off burns significantly more energy relative to the alternative of
staying on for an extended period - same way your car engine gets better
miles-per-gallon on the highway versus in the city with stop and go
traffic.  For this reason, staged cooling saves energy. 


Staged cooling has other benefits including tighter temperature control
and sometimes better de-humidification during part-load seasons,
depending on your system setup.








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From: bldg-sim-bounces at lists.onebuilding.org
[mailto:bldg-sim-bounces at lists.onebuilding.org] On Behalf Of Deepak
Sent: Tuesday, October 19, 2010 8:17 AM
To: bldg-sim at lists.onebuilding.org
Subject: [Bldg-sim] Difference between between a Single Speed DX and
Twospeed DX cooling coil


Can anyone tell me what is the difference between between  Single Speed
DX cooling coil and Two speed DX cooling coil and how two speed DX are
less energy consuming.

thanks in advance.


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