I have received this question generated by the LEED v4 Minimum Energy Performance calculator stating "The fan demand (as reported in the Performance Outputs tab) for the baseline and/or proposed exceeds the fan power as reported in the Air-Side HVAC tab (total system fan power) by more than 5%. Ensure that the values reflected in the Air-Side HVAC sheet are accurate and appropriately reflect the modeled fans."
I added the baseline fan demand in the Air-Side HVAC tab based on the values generated from eQuest reflected from what I was required to do according to Appendix G for System 3 and System 9. I added the proposed fan demand in the same tab based on the Mechanical Schedule of the recent project drawings. In eQuest, I made sure the fan power for each unit in the proposed was modeled with the same values taken from the Mechanical Schedule. By that logic, the fan power that eQuest generated for the baseline and proposed models would match the fan demand noted in the Air-Side HVAC tab. After running simulations for both models and adding them to the Performance Outputs tab, the total ventilation fan power for both models exceeded the fan demand for both baseline and proposed in the Air-Side HVAC tab. How can that be? I made sure the fan power for each individual system was identical in the Air-Side HVAC tab and eQuest for both the baseline and proposed models. Even the ventilation operation schedules for both models are identical.
Marcus Sheffer
LEED Fellow7group / Energy Opportunities
LEEDuser Expert
5914 thumbs up
August 22, 2018 - 11:15 am
If they are constant volume fans the demand and the fan power should match. If they are variable speed fans the demand should be somewhat less than the fan power.
Are you getting the fan power from the SV-A reports? Are you entering each system individually in the Air-side HVAC tab? Is there any energy recovery associated with any of the systems?
Edgar Arevalo
Associate19 thumbs up
August 27, 2018 - 11:39 am
For the Baseline, all fans are constant volume. And yes for the baseline, I am getting the fan power from the SV-A reports. I summed up the fan power for the baseline from SV-A report on a separate spreadsheet and copied it to the Air-Side HVAC tab under Supply Fan Power. There was nothing else from fan power to add on because there was no return/relief fan power to report. Exhaust Fan Power was modeled as a direct interior load at the meter, since it was a non-receptacle process equipment and had to be modeled exactly as the exhaust fan power from the Proposed model. But totaling the fan power of both supply fan and exhaust fan would still give me half of what the PS-E report calculated as total fan demand for ventilation fans in the Baseline model.
For the Proposed,
Marcus Sheffer
LEED Fellow7group / Energy Opportunities
LEEDuser Expert
5914 thumbs up
August 27, 2018 - 3:47 pm
Did you perhaps enter a multiplier by mistake? This shows up on the SV-A report. That might be likely if it is exactly double.
Edgar Arevalo
Associate19 thumbs up
August 29, 2018 - 9:49 am
Sorry for the late reply, I was pulled into another project the whole day yesterday. I checked each system in the SV-A reports, all multipliers are set to 1. Nothing has been doubled.
Marcus Sheffer
LEED Fellow7group / Energy Opportunities
LEEDuser Expert
5914 thumbs up
August 29, 2018 - 9:26 pm
Hummm, not sure then. I would post the question in the eQUEST listserv found at onebuilding.org.