I'm modeling a Pkgd Var Vol rooftop unit with VAV boxes in eQUEST version 3.65 and I have a ventilation issue. The issue is this...
Although I enter an Air Flow rate in cfm for each VAV box, the program insists on increasing my cfm by 1.05% when I run a simulation. I can't seem to force the program to model the ventilation cfm that I've entered. How can I stop eQUEST for increasing by hardwired ventilation cfm? What factors do I need to modify to run a simulation with the ventilation quantities for my scheduled cfm?
thanks,
Michael Schaefer - P.E.*, LEED AP
Licensed in Kansas, Missouri, and Colorado
Is your weather-file-location at a high elevation? I think eQUEST assumes all input CFM are at standard atmospheric pressure (aka- sea level) and adjust the flows to compensate for decreasing pressure at higher elevations.
I *think* you can manually adjust the elevation to undo this adjustment, but I'm not sure what other impacts it might have on the simulation.
Nathan Miller, PE, LEED AP BD+C - Mechanical Engineer/Senior Energy Analyst
RUSHING | O 206-285-7100 | C 207-650-3942
www.rushingco.com
Mike,
The program is accounting for the density of the air at the elevation of the project site compared to density at sea level. To make the output airflows match you input airflows, you need to change the elevation to zero.
In the "Project & Site" module, click on "Site Data" along the left side. In the "Site Properties" window that pops up, and in the "Basic Specifications" tab, enter "0" for Altitude.
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Keith Swartz, PE | Senior Energy Engineer
Seventhwave
608.210.7123 seventhwave.org
Michael,
If you are referring to the CFMs in the SV-A report being 5 % higher than what you input, check the Altitude Factor in the same report. Your inputs into eQuest are in standard CFM (i.e. at sea level), while the reports are in site CFM (i.e. at site altitude). So if your altitude factor is > 1.0, the reported airflows will be higher than your inputs. You can check by selecting an alternative location at sea level.
Regards,
Robin
Robin Thornton, CMVP, CEM, LEED AP BD+C web: www.celgruen.ca
Associate
CEL GRUEN, Sustainability Group
Crossey Engineering Ltd.
FUTURE FOCUSED | INNOVATIVE | ADAPTIVE
2255 Sheppard Avenue East Suite E-331
Toronto, Ontario, M2J 4Y1
office: 416.497.3111 ext. 659
email: robin.thornton at cel.ca