Comparison Of Hermetic Scroll And Reciprocating Compressors


I recently received the following question: Mike – have you posted a blog about the difference between recip and scroll compressors?   We run into some resistance in some areas because we don’t use all scrolls.  We try to answer this by stating that we design the compressor to fit the application, and that scrolls are not always the best fit.  But you know contractors and if they think scrolls are better, we lose.

Well, I have not posted anything on this subject and I know the factory answer is just what is stated above —  that the compressor selection is based on best performance fit for the product.  Most manufacturers can use either reciprocating or scroll compressors.  It usually is not a matter of “space” since either will usually fit in the cabinet.  I’m sure most manufacturers would love to have to stock only one type of compressor but, with the government changing efficiency requirements and manufacturers trying to keep up with those requirements, sometimes a recip gives the best efficiency and some times a scroll does.

Now, as I have stated in the past, I am not an engineer so, as a “student of HVAC”, I started to research the subject.  Believe it or not, PURDUE UNIVERSITY Department of Engineering actually did a study on the very subject.  Below is a link to a paper they published and I have copied and pasted the conclusions they found from that paper.

Over all, the scroll has some advantages but not in all cases which takes us back to why engineers use both types in equipment design.  Keep in mind that engineers are designing to meet efficiency requirements.  One of the disadvantages of scrolls is the higher power consumption by the scroll at  overcharged condition. In fact, they found  COP is reduced with significant under- and over-charging — and we all know that charge in today’s equipment is becoming more and more critical. So if a tech is not taking their time, and is not accurate on their charge, the scroll could be less efficient than the recip. 

CONCLUSIONS: A series of steady state performance experiments were carried out using a scroll and a reciprocating compressor at two condenser operating conditions. The results show that the scroll compressor generally produces cooling capacities and COPs that are equal to or greater than the reciprocating compressor. The performance of the scroll compressor improves relative to the reciprocating compressor at the higher condenser temperature. The use of a liquid injection system allows the scroll compressor to produce lower discharge temperatures than the reciprocating compressor.

A number of tests were also carried out to investigate the performance of both compressor types at varying charge levels. The scroll and reciprocating compressors show similar characteristics for cooling capacity and COP with respect to system charge level. The deterioration of the cooling capacity in the scroll is slower during overcharging than in the reciprocating but this is offset by the higher power consumption by the scroll at  overcharged condition and so the COP variation is similar. Generally, COP is slightly reduced with under-charging and significantly reduced with over-charging.

The scroll and reciprocating compressors also show similar characteristics for superheat and subcooling with respect to charge level. For both compressor types, superheat decreases with increased charge level and subcooling increases significantly at charge levels above the nominal. The scroll compressor produces slightly greater superheat and considerably greater subcooling than the reciprocating compressor. The increase in subcooling for the scroll design is a result of the liquid injection system reducing the amount of de-superheating required in the condenser.

The results suggest that scroll compressors may deliver performance advantages over reciprocating compressors at some operating conditions, particularly at higher condenser temperatures and this is because of the lower discharge temperature observed in the scroll. Both compressor types exhibit the same general characteristics with respect to system charge. In particular, COP is reduced with significant under- and over-charging. Superheat and subcooling are shown to be functions of system charge level for both compressors and thus may be used as a general indicator of charge level, irrespective of the compressor type.  (Taken from  Purdue University.   Purdue e-Pubs

Grace, I.; Datta, D.; and Tassou, S. A., ” Comparison Of Hermetic Scroll And Reciprocating Compressors Operating Under Varying Refrigerant Charge And Load ” (2002).  International Compressor Engineering Conference. Paper 1518. http://docs.lib.purdue.edu/icec/1518 )

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About yorkcentraltechtalk

I have been in the HVAC industry most of my life. I worked 25 years for contractors on anything from residential to large commercial boilers and power burners. For the past 23+ years I had been employed by York International UPG Division ( a division of Johnson Controls) as a Technical support/Service Manager but I am now retired. One of my goals has always been to "educate" dealers and contractors. The reason for starting this blog was to share some knowledge, thoughts, ideas, etc with anyone who takes the time to read it. The contents of this blog are my own opinions, thoughts, experiences and should not be construed as those of Johnson Controls York UPG in any way. I hope you find this a help. I always welcome comments and suggestions for postings and will do my best to address any thoughts, questions, or topics you may want to hear about. Thanks for taking the time to read my postings! Mike Bishop
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16 Responses to Comparison Of Hermetic Scroll And Reciprocating Compressors

  1. Michael J Stima says:

    I would like an explanation of 208/230 compressor operation at low voltage 206 and options to correct starting problems …. Does York make a 200V single phase unit?

  2. Hafizul says:

    Err..Mr,since you are an expert,would u help me with these basic-newbie problems?..,What is the different between hermetic,semi hermetic and reciprocating compressor?? how to identify and differentiate all of them?

    • Hermetic compressors, whether reciprocating or scroll and “sealed in a “can”. Semi-hermetic compressors are compressors that can be taken apart and parts changed and are usually cast iron shells.

  3. Damen Hall says:

    What would you think about a company that had created a way to remanufacture a Copeland scroll hermetic compressor and offer it back to the market place direct to dealers and technicians at a fraction of the cost. For example a 34,000 208/230 single phase unit or a ZR34xx-pfv for $400

    • re-manufactured semi-hermetic compressors have been in the market place for many years. If the re-manufactured scroll is (1) RELIABLE, (2) HAS A WARRANTY — AT LEAST 1 YEAR, and (3) is READILY AVAILABLE, then I do not see why this type of offering would not be just as acceptable. Also, look at the possibility of “partnering with a “national ” distributor like Johnstone Supply, or US Air along with dealer direct

  4. Saju mon p says:

    What is difrence between scrol compresser and reciprocating compresser how to function of scrol compresser????

  5. Syed says:

    thanks ..

  6. BiGG_D says:

    Ive seen articles before of people using refrig compressors for pneumatic purposes, a friend of mine has drawn my attention to a reciprocating york compressor that does 250CFM & seems to run ~275 PSI

    Any idea on how difficult this would be to convert & what kind of power would be required to make it perform?

    Thanks,
    D

    • Unfortunately,I never attempted to use an air conditioning compressor for pneumatic purposes so I can’t help you with this. You might try contacting your local York distributor the model number of the compressor you want to use and see of they might be able to help you out.

  7. Mark_U says:

    What is COP?

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