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  1. ypwtb

    MCA for convenience outlet on HVAC equipment

    Hello, Why is Trane using 150% of FLA for the electrical requirement of a convenience outlet on a rooftop unit in page 36 of this document? http://www.trane.com/Commercial/Uploads/Pdf/1025/iom.pdf Isn't this supposed to be the contribution of the outlet to the total MCA (minimum circuit amps)...
  2. ypwtb

    Psychrometric ratio formula and units

    Both true. I'm not sure how to use those observations to fortify a conclusion in this situation. Which of the two formulae in the OP do you count as defining the psychrometric ratio? Why that one? Or do you use some other definition? Thanks, Yittri
  3. ypwtb

    Psychrometric ratio formula and units

    The formula in this article http://en.wikipedia.org/wiki/Psychrometrics is like the latter of the two in the OP. And it also has k with units of "mass / (area * time)". This document http://engineer.msu.ac.th/CD_Conference/conference/IDS2002/PDF/0259.pdf Gives the units of k_y as (kg /( m^2...
  4. ypwtb

    Psychrometric ratio formula and units

    What is the usual formula for the "psychrometric ratio"? I find two versions in on-line documents: http://www.geocities.com/drying_guru/chapter1fundamentals.pdf r = h / (M_air k_y) http://www.probec.org/fileuploads/fl120336971099294500CHAP12_Dryers.pdf page 12-3: r = h_c /( k c_s) The...
  5. ypwtb

    Calculating air flow rate for UAFD system

    Hello, This web page http://www.cbe.berkeley.edu/underfloorair/designguidelines.htm says: Then what does? It seems that they try to explain: If there is a maximum acceptable ceiling-temperature value and a minimum acceptable supply air temperature, then a given total cooling load...
  6. ypwtb

    Elbow-tap flow meter formula

    Thanks for the replies. I did the derivation thing. It might have been easy in my college days. I won't say how difficult it was these days. The idealized formula for consistent units is: m_dot = pi/4 * sqrt(R * D^3 * delta_P * rho) Plugging in conversion factors to match the formula...
  7. ypwtb

    Elbow-tap flow meter formula

    Hello, The following formula for an elbow-tap flow meter W = 244 [SQ.ROOT SIGN] r * delta_p * d^3 * rho is given here: http://www.seilenterprise.co.kr/Korean/Technology/flowmetertypes.htm#Elbow A few questions: 1. Is this formula accepted as accurate? 2. How is it to be parsed? I don't...

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