[Equest-users] ASHRAE 90.1-2007 baseline fan flow

[Gastón Michaud F.]

Hello everyone,
I got the following comment from a LEED reviewer, and was hoping you guys could help me out.
"It is unclear whether the Baseline case fan air flow rates were sized based on a 20 deg. F supply-air-to-room-air temperature difference for each Baseline system because using the sensible heat equation (Q = 1.08*CFM*deltaT) with the total cooling capacity of 1,103,721 Btuh and total supply airflow of 15,656 CFM reported in Table 1.4.7A, it appears that a temperature difference of 65 deg. F was used. Update the model, provide input summary reports showing that the Baseline case air flow rates were sized based on a 20 deg. F supply-air-to-room-air temperature difference per G3.1.2.8, update Supplemental Table 1.4 to reflect the total Baseline Case air flow, and update the form to reflect any changes made."

The zone temperature is set to 75F and the MIN-SUPPLY-T is set to 55F, therefore it should be sized based on the 20 degree difference if I leave the airflow to be estimated automatically, am I correct?
The other issue is that the reviewer seems to be estimating the temperature difference using the sensible heat equation with the total cooling capacity, which is incorrect, right? If I use the sensible heat capacity, as it should be in the equation, the temperature difference drops to 30F; which is still high and I intend to correct it, but it is not 65F as mentioned by the reviewer.

I really appreciate your help.
Best regards,

  Ing. Gastón Michaud F.
  Tel.: (506) 2222-7529
  Fax: (506) 2256-5608
  From USA: 1-305-433-3668
  Calle 30, Avenida 0 y 2. San José, Costa Rica

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