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  1. #1
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    Variable Frequency Drives



    What are the advantages of using VFD (Variable Frequency Drives) with evaporator or condenser pumps other than electrical efficiency ?



  2. #2
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    Re: Variable Frequency Drives

    What's a condenser pump?
    Incr. electr. eff. IS the most important thing you can achieve with a VFD.
    Others: increasing evaporator, increasing lifetime of compressor, decreasing vibration,...
    It's better to keep your mouth shut and give the impression that you're stupid than to open it and remove all doubt.

  3. #3
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    Re: Variable Frequency Drives

    Hi Peter ,

    Thanks for your reply.

    In your reply , you said " increasing evaporator " ; what does it mean exactly ??

    Sorry , i used the term condenser pumps; i wanted to say the pumps which are used to circulate water through the condenser and cooling tower.

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    Re: Variable Frequency Drives

    Sorry, I meant increasing evaporator pressure.
    Condenser pumps: if your cooling tower has to work under partial load conditions for a reasonable amount of time, then you also can use a VFD on you condenser pumps to decrease power consumption.
    Electricity is becoming so expensive here that we have to search to a solution to reduce the energy of every component in the whole system.
    Last edited by Peter_1; 03-07-2011 at 12:40 PM.
    It's better to keep your mouth shut and give the impression that you're stupid than to open it and remove all doubt.

  5. #5
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    Re: Variable Frequency Drives

    Thanks for your prompt reply Peter ,

    saving electricity is a top priority for everyone.

    How VFD helps in achieving high evaporator pressure and how it increases the lifetime of compressor ??

  6. #6
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    Re: Variable Frequency Drives

    it reduces the start up inertia of the compressor,prolonging the life expectancy,also provides protection for missing phase

  7. #7
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    Re: Variable Frequency Drives

    VSDs also save on Maintenance costs and wear on associated equipment. Like you may only have to change the air filters 1/2 as often and v-belts 1/4 as often, bearings last much longer

    For control purposes on large complicated systems such as chilled water systems and condenser water systems with multiple chillers. Some compressors use this technology too.

  8. #8
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    Re: Variable Frequency Drives

    Thanks Tesla ,

    I have never seen a compressor connected to VFD.As peter replied that it also helps in increasing the evaporator pressure. Can anyone explain me how it effects the evaporator pressure.

  9. #9
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    Re: Variable Frequency Drives

    If refrigeration load less than design load, suction pressure can be increased.

  10. #10
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    Re: Variable Frequency Drives

    Hi Sumit
    If we slow down eg. centrif compressor under partial load conditions the pressures will tend to equalise where the suction will increase and the discharge will decrease. This will increase the COP of the compressor and the compressor will be more efficient. On top of that we will only use a portion of the power (electrical) to run the compressor. Most buildings are designed and controlled for comfort not efficiency. This is where energy management comes in. As all buildings are designed to maintain conditions in 95% of the hottest and coldest expected days There is a lot of room to save energy, wear and maintenance when there is only a 50% or 20% load on the building. On top of that we can refer to the ASHRAE comfort chart which basicly says that on a hot day the temp can rise to 26degC and a cold day down to 21degC or something like that. I recently worked for an energy management software company and were saving 10% to 30% on a group of buildings. The success came from a team effort on BMS, Mechanical Maintenance, Building Management and the Energy Management company who monitored via computer on a daily basis.

  11. #11
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    Re: Variable Frequency Drives

    Thanks Tesla,

    Again a good explanation by you and congratulations as you are contributing in saving the energy. All the best for future.

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