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# Revision history [back]

### LEED Baseline Building: G3.1.2.9

Hi, I have a doubt about System Fan Power with System 8.

G3.1.2.9 says: System fan electrical power for supply, return, exhaust, and relief (excluding power to fanpowered VAV boxes) shall be calculated using the following formulas:....

Moreover, G3.1.2.8 says: If return or relief fans are specified in the proposed design, the baseline building design shall also be modeled with fans serving the same functions and sized for the baseline system supply fan air quantity less the minimum outdoor air, or 90% of the supply fan air quantity, whichever is larger.

Therefore, I understood to apply the G3.1.2.9 method to the supply fan with 100% of design flow rate and to apply it again to the return fan with 90% of design flow (or the supply minus the outdoor air). So I get two different powers to apply to these fans.

My way of thinking appears to be wrong since the power is intended to be the sum of the supply and return fan. This can be noticed also from the 1.4 table.

Can someone make it clear? If the second method is the correct one: how do I redistribute this power between supply and return fans?

Thank you

 2 retagged __AmirRoth__ 4388 ●5 ●16 http://bleedinggreenna...

### LEED Baseline Building: G3.1.2.9

Hi, I have a doubt about System Fan Power with System 8.

G3.1.2.9 says: System fan electrical power for supply, return, exhaust, and relief (excluding power to fanpowered VAV boxes) shall be calculated using the following formulas:....

Moreover, G3.1.2.8 says: If return or relief fans are specified in the proposed design, the baseline building design shall also be modeled with fans serving the same functions and sized for the baseline system supply fan air quantity less the minimum outdoor air, or 90% of the supply fan air quantity, whichever is larger.

Therefore, I understood to apply the G3.1.2.9 method to the supply fan with 100% of design flow rate and to apply it again to the return fan with 90% of design flow (or the supply minus the outdoor air). So I get two different powers to apply to these fans.

My way of thinking appears to be wrong since the power is intended to be the sum of the supply and return fan. This can be noticed also from the 1.4 table.

Can someone make it clear? If the second method is the correct one: how do I redistribute this power between supply and return fans?

Thank you