Horsepower to tons/ref. conversion ?

[Hank Hill]

We have a cascade system with a 15 hp low stage compressor and a 30 hp high stage compressor. Is there an easy way to figure the tons of refrigeration this system is putting out? The high stage has a tower water cooled condenser. Low stage is 508B and high stage is 22.

[chemi-cool]

Hi Hank,

It depend on evaporating and condensing temp of the compressor.

Wouldn't it be easy to to look in the compressor manufacturer catalogue and choos it from there?

Chemi :)

[Hank Hill]

Actually we were wondering what affect the cascade aspect has on the tonage rating? An older similar unit at this site has 4 30 hp compressors, and another has 2 50hp compressors, while our cascade systems do the same with a 15hp and a 30 hp, it appears that the cascade exponentially increases the capacity. It is hard to grasp how this can be possible, but it is, it works.

Our evap temp is -80C and our cond. temp is -10C for the low stage and the high stage is -10C for evap and +20 to +35C condensing temp.

[TXiceman]

I do not know of any way to convert input power (HP) into tons of capacity. There are too many variables, such as evaporating temps, condensing temps, stages of economizing, type of refrigerant used and so on.

Like suggested above, use the compressor manufacturers data and your actual operating conditions.

The 30 HP compressors may not be drawing 30 HP, but may actually be drawing 23 or 24 HP. The 50 HP compressors may be drawing 45 HP. So you can not compare motor size to get an accurate comparison.

Ken