New to eQuest modeling - Adding HVAC systems

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Hello group,

I'm using eQuest to model the energy use of a 40,000 ft? commercial
building that was once three separate internal spaces inside the same
building. Over the years they consolidated into one building internally.
however the HVAC systems have been designed for each of the three spaces
prior to consolidation. They now want to add solar and I've been asked to
model the current energy use and recommend upgrades to reduce their energy
use before they size the solar. My goal is to redesign the entire air
distribution system and upgrade a subset of DX systems and eliminate the
others. They are getting a new roof and I believe that will help air seal
the building reducing the stack effect such that then BTUs needed to heat
and cool the space will be reduced and their existing 14 units of varying
sizes totalling 100 tons of cooling can be reduced to maybe 60 tons. How
do I model the 14 units? As one HVAC system of 100 tons assigned to zones
or individual systems assigned to zones?

Kind Regards,
Mark Stout, President
Lighting & Mechanical Acceptance Testing
CALGreen Inspector/Plans Examiner

Apollo Energies, Inc.
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mark.stout's picture
Joined: 2013-08-06
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If I?m understanding the situation there are 14 existing HVAC units that served three separate ?suites? and now one occupant will control the whole building allowing sharing between the 14 HVAC units such that several may become redundant. The total capacity is about 100 tons.

In the new design you will have combined air distribution and expect the total load to be 60 tons, including air sealing. Hopefully a lighting upgrade as well which will help reduce the loads unless the system is already modernized.

Do you need to model the existing case? If the only decisions are the new system, then just model the building as it will be configured.

If the modeling is being used to support third-party financing then you may need to model the existing case and calibrate to utility bills. In that case you?ll have an envelope and spaces, and zones that will be the same in both cases, but you?ll be free to serve these from one set of HVAC in your baseline and new HVAC in the proposed case ? focus on defining the zones so that you can change the scenario from baseline to proposed. My main tip would be to make more granular zones in case you aren?t sure which will be served by what combination of HVAC in the future. If you make larger zones in the baseline you may find it limiting in how to change it going forward. The smallest amount of zones may be 14 ? one for each existing HVAC unit, but may be more if there are variations in use and occupancy within those system service areas and differences how you may combine them in the future. i.e. if you take one of the existing HVAC units and share its zones to two different new HVAC systems you?ll have to model that one as at least two zones in the baseline.

I hope this helps.


David S. Eldridge, Jr., P.E., BEMP, BEAP, HBDP, GGA

Direct: (847) 316-9224 | Mobile: (773) 490-5038

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David Eldridge's picture
Joined: 2012-05-08
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