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  1. #1
    Join Date
    Apr 2005
    Location
    Australia : Queensland
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    802

    Question

    i am only a 1st year apprentice can any i helpme with this. enthalpy control of economiser cycles. i do not even know what it is just got a email from my trade teacher saying maybe have a look at this.

    [Edited by fridg on 10-15-2005 at 08:57 AM]

  2. #2
    Join Date
    Mar 2004
    Location
    SE Michigan
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    17,995
    Enthalpy is a measure of total heat content of the air,and the enthalpy control senses both temperature and humidity. An enthalpy control will have 4 fixed settings A B C and D. Each setting defines a range of conditions at which the control will operate. The operating ranges can be better visualized if you look at a psychrometric chart. You can see by the shape of the bands that as humidity decreases the allowable temp. for free cooling increases, which is why enthalpy is a better measure of suitability than temperature alone. There are also differential enthalpy controls, these sense the difference between outdoor air and return air enthalpy.
    Behind the ostensible government sits enthroned an invisible government owing no allegiance and acknowledging no responsibility to the people.

    Theodore Roosevelt

  3. #3
    Join Date
    Mar 2004
    Location
    SE Michigan
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    17,995
    Hope this helped. I have more info. if you need it.
    Behind the ostensible government sits enthroned an invisible government owing no allegiance and acknowledging no responsibility to the people.

    Theodore Roosevelt

  4. #4
    Join Date
    Apr 2005
    Location
    Australia : Queensland
    Posts
    802
    Coolwhip. I know how to read an enthalpy chart we learnt the basics of this in our 1st year of college but exactly what is the economiser cycles. and also he mentioned DDC control formats and protocols,i dont want to get confused yet but understanding the basics would be a help.

  5. #5
    Join Date
    Oct 2005
    Posts
    26
    Fridg, do you know what an econimizer is?

    With the wording used in your question it's hard to understand what the question is.

  6. #6
    Join Date
    Apr 2005
    Location
    Australia : Queensland
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    802
    the original question was what is enthalpy control of economiser cycles.I know what enthalpy is. I think an economiser is a vessel to help with system efficiency ? and i do not even have a clue what DDC control formats and protocols are i am currently apprenticed to a manufacturing company so i might not have the experience you people have.

  7. #7
    Join Date
    Oct 2005
    Posts
    26
    The term economizer is used when the out door environment can be used to aid in the cooling process instead of a mechanical means. In this case we would be introducing out door air into the building if the enthalpy was low enough to allow us to use this air. In a typical DDC system, both the indoor and out door air enthalpy is measured, when ever the outdoor air is at a lower enthalpy than the indoor air, free cooling is enabled. The building will then basically use fresh air for part or all of the cooling requirements.

    P.S DDC is Direct Digital Control and Protocols are the language they use to send this information back and forth. Like the internet is IP and Email is SMTP.. DDC use protocols like Lon, Bacnet, N2


    Hope this helps...

  8. #8
    Join Date
    Apr 2005
    Location
    Australia : Queensland
    Posts
    802

    Hmm

    Hey i like the sound of these economisers

  9. #9
    Join Date
    Oct 2005
    Location
    Vancouver, Washington
    Posts
    4

    Talking

    You wouldn't believe how much money they save on an office building when operating correctly with a DDC system...

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