All,
I am modeling a portion of a 100% outside air lab in a type 5A climate zone. The area is below ground/has interior walls so there is no fenestration. The system has two chilled water air handling units and VAV boxes with zone reheat. The two AHU's run 24/7 at a constant CFM because the supply air is driven by a required air change rate per room type.
My problem is:
- I have too many unmet cooling hours when allowing e-Quest to auto-size the cooling coil capacity of the air handling units
Diagnosis:
- The delta T of the cooling coil never gets above 7 degrees F any day of the summer.
- e-Quest severely undersized the cooling coils from a design day. (I have calculated the design day cooling load by hand)
- No warnings in the Sim report
I have tried troubleshooting the system for a couple of days but am unable to find the reason e-Quest is under sizing the cooling coil capacity. I have attached the .inp file. Any suggestion are greatly appreciated.
Thank you,
Brad Huff, E.I.T.
One quick and easy fix is to increase the sizing factor found in the cooling
tab. Currently you have it set to 1.15. I tried setting it to 2.0, and there
were no more unmet hours.
__________________________________________________________
Eddie Corwin
All,
Thank you for your input. While the sizing factor did eliminate the unmet hours it did not correct the problem of e-Quest severely under sizing the system. The problem was related to the weather file and design conditions e-Quest was using. The weather file was correct for the climate zone but in examining the LS-C report, the cooling design conditions were 56 F Dry Bulb in September, far from the realistic design day of 91 F Dry Bulb in June. To correct this I created both a cooling and heating design day in the "Project & Site" tab.
Thank you,
Brad Huff, E.I.T.