[Bldg-sim] Fan power calculation for proposed model

Duggin, Cory Cory.Duggin at tlc-eng.com
Tue Sep 1 14:08:58 PDT 2015


It is my understanding that the proposed model should always be the design values used in selecting the fan not what is calculated by the energy simulation.  I agree the fan most likely will not operate at that flow rate, but that is what we have fan curves for.

Cory Duggin, PE, LEED AP BD+C
Associate/Energy Modeling Wizard, j.g.
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TLC Engineering for Architecture
direct:

615-346-1939



From: Bldg-sim [mailto:bldg-sim-bounces at lists.onebuilding.org] On Behalf Of Nicholas Blanton
Sent: Tuesday, September 01, 2015 4:03 PM
To: bldg-sim at lists.onebuilding.org
Subject: [Bldg-sim] Fan power calculation for proposed model

Please comment on the following:

Based on Table G3.1.10.a, for an HVAC system in the proposed design, the system is determined by the following:

"Where a complete HVAC system exists, the model shall reflect the actual system type using actual component capacities and efficiencies."

In design of AHU systems, the scheduled or nameplate flow rate of the equipment is typically higher than the design flow rate of the system, as calculated by the simulation software. The system fan power calculation is based on the efficiency of the fan and ultimately the design flow rate of the fan. Also, in operation the fan typically does not operate at 60 Hz at peak flow rate, suggesting that the operating flow rate in this condition is more in line with the design flow rate calculated by the simulation software, rather than the nameplate flow rate of the equipment.

For these reasons, it is likely the case that the fan power calculation should be based on the design flow rate calculated by the software, rather than the nameplate flow rate.

Thanks,

Nick Blanton

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