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  1. #1
    Join Date
    Mar 2011
    Location
    Mumbai,India
    Posts
    11

    Fieldpiece HVAC Guide

    Hi, I am thinking of buying Fiedpiece Instrument HVAC Guide. I would like to know in order to check super heat data required is DB for out door and Return WB. One of videos highlights the same on youtube where the wetbulb probe is place in return air duct of AHU. Confused why return wet bulb temp is required,where i presume the temp of the suction pipe near the exit of the evapoartor is to be recorded after the TXV bulb. Hence, what is the importance of return wet bulb temp.

    regards
    SK

  2. #2
    Join Date
    Jul 2010
    Location
    nebraska
    Posts
    1,629
    Require SH goes up and down based on indoor wet bulb and outdoor drybulb temps. Got to know both to get it right.

  3. #3
    Join Date
    Dec 2008
    Location
    Ontario Canada
    Posts
    552
    Indoor WB gives TOTAL heat load on evaporator (latent and sensible), heat load will change expected operating temperatures and pressures

  4. #4
    Join Date
    Jul 2009
    Location
    new york
    Posts
    666
    I just bought hvac guide 2 on ebay for 110.00 in perfect shape .

  5. #5
    Join Date
    Mar 2012
    Location
    West Chester, PA
    Posts
    516
    Return air wet bulb is an indicator of enthalpy which is 'total' heat sensible and latent(in this case, heat associated with moisture in the air). You need to know how much heat is in the air your conditioning. There is no latent heat associated with rejection in the condenser so only the outdoor DB is required.

  6. #6
    Join Date
    Aug 2003
    Location
    Fort Worth, TX
    Posts
    11,376
    For split system and package HVAC common in the USA, it's typical to measure suction superheat near the compressor vs. at the outlet of the evaporator. Measuring superheat at the evaporator outlet is useful if the system has a TXV in order to determine if the valve is controlling evaporator superheat properly. Suction superheat near the condenser or compressor will almost always be higher than at the evaporator outlet.

    Return air wet bulb is an important measurement as it factors in the latent load the evaporator has. It also is part of an equation used to find correct suction superheat corresponding to indoor wet bulb and outdoor dry bulb.

    This thread might be better served in the Tools section.
    • Electricity makes refrigeration happen.
    • Refrigeration makes the HVAC psychrometric process happen.
    • HVAC pyschrometrics is what makes indoor human comfort happen...IF the ducts AND the building envelope cooperate.


    A building is NOT beautiful unless it is also comfortable.

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