CBECC-Com 2019: Difference in Fan Energy

User - I’m running a simulation in CBECC-Com 2019 for an 8 story office building, and the proposed model is failing by ~11%. The model was originally failing by 15% but we changed the WWR and skylight to roof ratio to match the Standard model (40%/5%) to see what was causing the disparity.

The proposed HVAC system is VAV with reheat, with chilled water supplied from a central plant. The hot water is supplied by WWHPs but these are modeled as two gas boilers since we can’t currently model a HP boiler in CBECC-Com. Basically, the proposed design is nearly identical to the standard so I’m not sure why we’re failing by so much – the proposed heating, cooling, and fan TDVs are the main culprits.

We used DView to compare the standard and proposed SQL files, and we found that the fans in the proposed model were running outside of the normal hours of operation, while the baseline fans were not. Given that the schedules are the same in the Standard and Proposed models, do you have an idea of what could be causing this difference? The image below is a comparison of the fan energy used by the VAV supply fans serving level 1 for both Standard and Proposed models.

Reported by: joesinger12

Original Ticket: cbecc-com/tickets/3255

joesinger12 / TestTicketTransfer

CBECC-Com 2019: Difference in Fan Energy #96