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NC-v4 EAp2:Minimum energy performance

Modeling System 5 per floor

Hi I am modeling a building with baseline system as 5 now based on Table G 3.1.1 , it says we need to model 1 VAV system per floor, now In reality I have 4 VRF units per floor , should I model one system 5 for all those 4 units ? Also for 2nd floor I have 4 VRF units but some of them are serving level-1, if I model system 5 for floor 2 , should I exclude the spaces on level-1 but in that case we wont be modeling based on Table G3.1.7 which says thermal zones in baseline model should be modeled the same way modeled in proposed.

 

TIA

 

Rajat

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Marcus Sheffer
LEED Fellow
7group / Energy Opportunities
LEEDuser Expert
4454 thumbs up

Thu, 08/24/2023 - 20:14

No you should model one system 5 per floor. In the case of the 4 VRF units you essentially have both 4 systems and 4 HVAC zones. On your typical floor you model one system 5 with 4 HVAC zones. For your second floor you should model one system 5 and again 4 HVAC zones but one of them is on the first floor. For the first floor you again model one system 5. Don't confuse systems, HVAC zones and thermal blocks. A thermal block is merely a collection of HVAC zones grouped together to make the model simplier. In order to do so all of the zones in the thermal block should share similar thermal conditions.  You can simplify your model by creating thermal blocks in alignment with the exception noted in Table G3.1-7 Proposed.

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