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  1. #1
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    compressor options



    Hi,
    I am trying to design an electrical auto air conditioning system. I calculated the load to be about 8000 btu, and assuming I will end up with a high cop system I am searching for a 600 Watt compressor. I wish to control capacity of the compressor threw its speed, and I wish to have a three faze electrical system. What are my options? Are there any hermetic three faze compressors (like the danfoss bd sires) or I have to run a “regular” auto compressor coupled with a motor?
    Thanks for the help.
    Maxim.



  2. #2
    Join Date
    Dec 2002
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    Malaysia
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    Re: compressor options

    Hi,

    You're not going to get any 3 phase compressors at 8000 btu/h requirement.

    Thats a single phase fractional - similar to hermetic recips from Copeland, Tecumseh, Danfoss or Embraco. Or you can use rotary types e.g. Mitsubishi etc.

    As for your high COP requirement, I guess you saying that you want the compressor to deliver 8000 btu/h but consume 600watts ? You should be able to...8000btu/h is less than 1 hp or about 700 W - so you should get 700/600 = 1.2 (COP) which actually is not really great.

    Regards !

  3. #3
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    Re: compressor options

    8000 btu is 2340 watt. so if i have a 600 watt compressor ill end up with a 3.9 cop.
    actualy danfoss has a small 3phase compressor (the bd family) but its too small for me. i'v thought about using two bd 35 compressors.

  4. #4
    Join Date
    Nov 2005
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    Re: compressor options

    IIRC, the Danfoss BD compressors are actually inverter drive DC compressors designed for automotive and solar applications. From the 8000BTU/hr requirement, I guess you're trying to cool something big like a bus or RV? 5000BTU/hr is enough to cool about 100 to 150 square feet of room.
    I believe Danfoss has a special version of the BD compressor designed to be paralleled.
    "If Hannah was an air handler, I would be a condensing unit so I could open her TXV and pump my refrigerant through her coils." - a HVAC friend of mine

  5. #5
    Join Date
    Feb 2005
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    Hong Kong
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    Re: compressor options

    hi all, a few comments which you may wish to consider.

    aaa. dont confuse compressor COP alone with overall system COP. with system COP you would need to consider input Watts of 12v/24VDC cond & evap motors in add'n to Danfoss compressor input Watts.

    bbb. these types of hermetics are more suited for "parked up" or night standby use of RV, blood bank bus etc etc. "Surviv-ability" over the road of a hermetic with prolonged use would be a concern due to quite extreme shock loads on road. That's why industry traditionally tends to use "open drive swashplates" of the Sanden/Unicla/TAMA-Zexel/Denso types. Having said that, verify if that Danfoss hermetic is a piston type or rotary - the latter may be better of the 2. A lot of research is currently underway on reliable , dedicated electric 'road' compressors for future hybrid and electric vehicles - dont know it's there yet. These compressors will be req'd for both pax a/c and refrigerated transport on small to medium 3^4 metre delivery vans. Both quite different applications!

    ccc. Transport a/c usually rated @ 35/27/19C condition or 95/80/67 degF from ARI/ASHRAE. Small shuttle bus, like USA hotel shuttles or MB Sprinter,Toyota Coaster typically rated 15to 25,000BTU/hr < typically using > 2oo to 300cc compressors>. Todays larger cars, SUV. jeeps would need the 8 to 10,000BTu/hr sizes < using 140 to 200cc comps>, at least in sub-tropic / tropics.

    regards

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