Dear Experts,
I am straggling to input Fan Power in the baseline model (System 6 - Packaged VAV with PFP Boxes) and have the following issues:
1- In Table 1.4.6 - General HVAC, there is a note for this type of system that requires
“All Baseline fans in parallel VAV fan-powered boxes sized for 50% of peak primary airflow and modeled with 0.35 W/cfm fan power and a minimum flow setpoint of 30% of peak (or minimum ventilation rate) per G3.1.3.14”.
Supply and return air of the system are equal, 49,202 cfm for each. Based on this cfm, supply fan power and return fan power is 17.22 KW (49,202 * 0.35). This number is different with the figure from ASHRAE 90.1-2007 Baseline Fan Power Calculator (The spreadsheet from 7group). In addition, when I input the supply and return cfm and 17.22 KW for both fans in “Table 1.4.7A - Baseline Air-Side HVAC System Schedule”, it indicates “Allowed Fan Power” to be 55.4 KW and it would be red marked with any other numbers input as system fan power.
2- In eQUEST’s “Fan Power and Control” screen, the input boxes for supply and return design KW/cfm are grayed out (n/) and I cannot input any data for the fan powers.
I would truly appreciate your comments,
Morteza
Marcus Sheffer
LEED Fellow7group / Energy Opportunities
LEEDuser Expert
5907 thumbs up
September 17, 2013 - 10:21 am
1 - The 0.35 W/cfm is in addition to the system fan power calculated under G3.1.2.9. This value is determined at each individual box based on its air flow. The spreadsheet only calculates the G3.1.2.9 baseline fan power for the major system fans and does not include the fan-powered boxes. Table 1.4.7A will only accurately calculate the baseline fan power if you enter each individual baseline system in a separate column. If you add everything up and put it in one column the baseline fan power will calculate slightly lower than the total of each system individually.
2 - Are you sure you have entered the correct baseline system? That is the only reason we can think of for the boxes being grayed out.