[Equest-users] Night Precooling Thermal Mass

[Amol Mehta]

Hi Guys,

I am trying to model nigh pre-cooling in E-quest. I was looking through
Archives but was unable to solve the problem. I have attached pd2 and inp
file for the project. Basically every thing is default from E-quest except
following items: 

Detail Data Edit: E-quest 3.63

Building Shell Components:

1) Screen1: Office Building High Rise
2) Screen3: Roof 4-inc concrete with R-18 Insulation/ Wall 10-inch Concrete
no insulation
3) Screen12: Operating Schedule: Typical Use: 8.00 AM to 10.00 PM (MF), SUN,
SAT, Holiday Closed

Air-Side System Types:

HVAC System 1:
1) Screen1: Dual Duct System (chilled water/ hot water coil)
2) Screen2: E-quest Default Values
3) Screen4: Fan Type: Forward Curved Centrifugal
4) Screen5: Fan Schedule: Fan Operates 5-hours before and 1-hour building
occupancy schedule. This is what currently implemented at the site. Fans are
run 5-hours before occupancy in order to pre-cool building and use thermal
mass of the building. 
5) Screen6: E-Quest Default Economizer 70F
6) Screen7: OA reset on Hot and Cold Deck.

Now my question is if I simulate this model and see hourly report I see
cooling load at 3.00 AM in the morning. I know my fan scheduled to run from
3.00 AM to 11.00 PM, but why it's using chilled water when it's cold
outside. If I simply match fan schedule to building occupancy schedule I see
savings on both chilled and hot water use. 
Also if set Night Cycle Control in Detail Data edit to Night Vent Schedule
(When Scheduled) with new ON/off Schedule (from 3.00 AM to 11.00 PM), Night
Vent Delta T = 5F, my energy consumption is lower than running fans from
3.00 AM to 11.00 PM without night vent but still higher than running fans
from 8.00AM to 10.00PM. I am not getting any credit for thermal mass and
pre-cooling, unless I am modeling incorrectly. Any help is appreciated.
Thank you.

Regards,

Amol Mehta | Mechanical Engineer | P2S Engineering, Inc.
T 562 497 2999 | F 562 497 2990 | M 858 354 6250
5000 East Spring Street, 8th Floor, Long Beach, CA  90815

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