[Equest-users] ASHRAE Appendix G and 20 deg Delta T

[Brian Goldsmith]

Hi Everyone,
I am trying to size my baseline for the 20 deg T between supply air temp and room temp. I have done many searches on this and have found a partial answer to my question, but not an exact answer. When I set MIN-SUPPLY-TEMP=55 for each system and DESIGN-COOL-T=75 for each zone, I get some very low CFM/Ton values. I have three systems: two System 6 VAV with PFP and one System 4 Heat Pump. The System 6 values are 280 and 284 CFM/ton, and the HP value is 388 CFM/ton, as shown in the system summary reports. Doing a quick Q=1.08cfm*dT check, the delta T for the systems are 39.5, 39.2, 28.6 deg T respectively. Am I doing something wrong here? One way I thought of fixing it would be to take the calculated cooling capacity, and calculate the CFM using a 20 deg dT, then plugging that CFM into each zone. Any thoughts or suggestions? Thanks.

Brian Goldsmith, LEED(r) AP
Design Engineer
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97 E. Brokaw Road, No 300
San Jose, CA 95112
main    408.487.1200
direct  408.487.1217
www.atce.com<http://www.atce.com/>


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