unloaders on refrigeration compressors

[imok2]

I have a question I don't really know the answer for maybe some of you refrigeration engineers can tell me why you seem to never find unloaders on refrigeration equipment as opposed to finding them on air conditioning equipment,now I know about the heat load changing but doesn't it also change in refrigeration? I have worked both sides but never thought much about it.

 

[cjw81]

imok- I have worked with 100 ton compressors in a refrigeration system- it happened to be for a skating rink, if I remember correctly there were six compressors (R-12) operating in parallel to chill calcium chloride brine. This is a perfect example of load control utilizing unloaders.

 

[Xtrema]

Call a Copeland Corporation application engineer. They make and sell both types of compressors and know the answers.

Refrigeration load does change, especially in grocery stores. For example, all the opening and closing of reach-in cases occurs during peak human traffic times, and overnight the loads are minimal.

 

[kevin1313]

Many of the market rack systems I work on employ both unloaders and compressors staging as a means of responding to various load conditions

 

[klrogers]

Unloaders and other forms of capacity control are used in both refrigeration and a/c systems, both have advantages and disadvantages. Consideration must be given for flow rate thru' pipework, oil return, suction line temperatures, compressor cooling, condenser load etc.
Each design must be evaluated to provide the best possible system