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  1. #1
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    Compressor current draw



    I have 2 copeland compressors, an r22 CRK3, and a R410- ZPS40.

    Interesting thing is that, given the same condensing temp, the R22 pot has an increase in current draw as the Evap temp increases and the R-410 pot has a decreasing current draw under the same conditions.

    Anyone know why?

    CRK3 0325 PVF 230 performance.pdf
    ZPS40K4E performance.pdf



  2. #2
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    Brian_UK is online now Moderator I am starting to push the Mods: of RE Site Moderator : and general nice guy
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    Re: Compressor current draw

    Nope, what was the prize for the correct answer ?
    Brian - Newton Abbot, Devon, UK
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    Re: Compressor current draw

    Hi MIke

    current draw is dependent on both high / low pressures

    the further apart the pressures are the more current draw

    the closer together the lower the current draw

    if you have fan speed control keeping a constant head pressure

    then as suction pressure rise's compressor work is lowered

    so maybe a miss print

    unless the R410a has fan speed control

    and the R22 does not

    R's chillerman
    If the World did not Suck, We would all fall off !

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    Re: Compressor current draw

    Hello
    Because the scroll has the "modulated capacity" ? Anyway, impossible to do more work with less power, as well as get the CT 30 C at 35 C ambient.
    Last edited by Yuri B.; 13-11-2011 at 08:56 AM.

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    Re: Compressor current draw

    It is to do with the difference in change of density, hence mass pumped.
    Look how the capacity changes with the different refrigerants.
    So reduced compression ratio reduced power.
    Increased mass flow more power.
    So it comes down to the combination of the 2

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    Re: Compressor current draw

    Quote Originally Posted by Brian_UK View Post
    Nope, what was the prize for the correct answer ?
    If it is a really good answer,I owe you a beer. If not you owe me a beer (incentive for good answers although I must pose hard questions or I will run out of beer money)

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    Re: Compressor current draw

    mike- its because the 410 version has a widget on it thus increased performance and reduced energy cost!- beer please!haha

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    Re: Compressor current draw

    Quote Originally Posted by chillerman2006 View Post
    Hi MIke

    current draw is dependent on both high / low pressures

    the further apart the pressures are the more current draw

    the closer together the lower the current draw

    if you have fan speed control keeping a constant head pressure

    then as suction pressure rise's compressor work is lowered

    so maybe a miss print

    unless the R410a has fan speed control

    and the R22 does not

    R's chillerman

    CM, it was a question that only came about because I have an old ASHP that has a good R22 pot and I am looking for the right one to use in my combi solar/evap project.

    If you just look at the performance data for the R22 pot, it would seem to be the opposite of what you said (unless I'm full of it, which is entirely possible)

    The question assumes all things being equal between the two.

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    Re: Compressor current draw

    Quote Originally Posted by mad fridgie View Post
    It is to do with the difference in change of density, hence mass pumped.
    Look how the capacity changes with the different refrigerants.
    So reduced compression ratio reduced power.
    Increased mass flow more power.
    So it comes down to the combination of the 2
    This makes me interested how adding external heat to the evap (solar) will affect the heat output and power consumption and whether it is worth it to add that heat (from a performance point of view).

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    Re: Compressor current draw

    Quote Originally Posted by Yuri B. View Post
    Hello
    Because the scroll has the "modulated capacity" ? Anyway, impossible to do more work with less power, as well as get the CT 30 C at 35 C ambient.
    The use is for a heat only HP so it won't be in use at 35C ambient. Otherwise, point made.

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    Re: Compressor current draw

    Quote Originally Posted by install monkey View Post
    mike- its because the 410 version has a widget on it thus increased performance and reduced energy cost!- beer please!haha
    Sorry Install, doesn't pass the beer test............try again

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    Re: Compressor current draw

    R22 in the cool mode, R410 in the HP mode ?

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    Re: Compressor current draw

    In this case it is a choice between an R22 comp that I already have or buying a R410A scroll for my test project.

    The interesting thing about the two comps is that the trends are the same, mass flow, capacity, efficiency and power, all increase with ambient but the current draw is opposite.

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    Re: Compressor current draw

    Probably you will need to look at the state equations of the 2 gases which will show the ratio of specific heats vary quite differently. This then yeilds a differant isentropic efficiency during compression with R22 only losing 4% from an evap temp of 12C down to 0C whilst R410A loses 13% over the same range. It is this big difference in efficiency which affects the power consumption and hence the amps drawn.You can find the state equations for both gases at Duponts website.Chef
    Last edited by Chef; 14-11-2011 at 10:01 PM.

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    Re: Compressor current draw

    Thanks Chef, I see you are in port to let your hands heal from hauling on the sheets.

    I'll go the Dupont to find the state equations but in your opinion, is the fact that one had a positive curve and one a negative curve, logical to you? I can understand them being both negative curves at different rates.

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    Re: Compressor current draw

    Hi Mike - I dont see any reason why it should be illogical because they are differant gases. The compression cycle is a polytropic process and the ratio of specific heats is a key factor in power absorbed as is the compressors efficiency.*

    If you look at the isentropic efficiency of the two gases at similar points one has a flat curve whilst the other has a marked drop. When you include the efficiency in the maths it just happens to show this characteristic. R22 is like this and has some quirks in many areas.

    The bell shape for R410A is also very differant to R22 and especially when you get to the 60 or 70C condensing temps. R22 is also much fatter and so has more specific heat rejection than R410A and runs way lower in pressure. Also the entropy curves have a differant slope so really trying to compare these 2 gases by simply looking at amps draw is difficult.

    In checking the tables you posted they seem correct and so I dont think it is a typo.

    Chef

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    Re: Compressor current draw

    If it was a typo it would be Copelands, LOL. Your explanation is very good so a beer goes to you (if you can be found in the middle of wild blue waves). I still have a HUGE amount to learn especially in the theoretical end of things (OK everywhere....)

    The original reason for looking at both comps is that I am designing the evap with both a hydronic coil and a DX coil in it and I need to decide if there is an advantage at all in using the R22 comp in this way. On first blush it appears 410A is the one to use.

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    Re: Compressor current draw

    I think you should post the conditions you have at evap and condenser and some ranges or limits as 410A is not normally recommended as a 22 replacement in older or existing kit? There is a sail through MacDonalds just down the bay so I will pick up a burger on your account if thats OK. Chef
    Last edited by Chef; 15-11-2011 at 03:12 AM.

  19. #19
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    Re: Compressor current draw

    Purely hypothetical at the moment. The kit is yet to be made and I just happen to have the older but little used R22 compressor. I haven't looked at the manufacture date but I was comparing that comp with the 410A comp to see if it was worth using as there is a replacement for R22 that copeland is promoting and I could use it in the old comp.

    McDees is OK as long as you don't heat the hash brown potatoe. Coffee is better than it used to be. Just mention my name.

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    Re: Compressor current draw

    I think 410 runs out of steam at around 66C so for a HP it may be a little off. Your project though. 22 might scrape 90c

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    Re: Compressor current draw

    True, it is hard to run a complete heating system in canada at liquid temps of 30-35C. Small market without backup.

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    Re: Compressor current draw

    Quote Originally Posted by MikeHolm View Post
    Sorry Install, doesn't pass the beer test............try again
    Mike,
    That is completly out of line!!! you said a good answer not the right answer!!! Install have one on me.

  23. #23
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    Re: Compressor current draw

    Ah yes, I see my mistake now. One must be be accurate in how one phrases things. OK install, looks like you have two beers coming to you....

    In that case Brian gets one too..
    Last edited by MikeHolm; 16-11-2011 at 03:46 PM. Reason: cant forget Brian

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    Re: Compressor current draw

    because you are so gracious, have one on me. And if I ever figure out the rep power thing you'll get one of those too.

  25. #25
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    Re: Compressor current draw

    Ahh, your kindness knows no bounds....

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