We are modelling a typical office building with multiple shells in e-Quest.
1. The proposed model(design) has floor level AHU's of type 'PIU' with terminal Fan powered boxes at the perimeter zones and terminal VAV boxes at interior core zones. The reheat at core zones were manually made zero because of the core zones require only cooling and that way it remains true to the design.
2. The baseline model has floor level AHU's of type 'Variable Air Volume' with reheat temperature given at the system level( not possible to give a reheat temperature at zone level).
Results show that the baseline heating is way worse than the proposed( by 40%) which doesn't seem right.
Core zones in the baseline model have a heating demand( confirmed through SV-A summary report) which may be the reason for the increased heating energy use.
Please advise if the system types selected are the right one's for the baseline model. And if it is right to have assigned a reheat at the system level which makes it to assign a reheat for the core zones automatically in the baseline model.
Balaji Jaishankar, LEED AP BD+C, EMIT | Energy Engineer [MEPC Logo]
MCGUIRE ENGINEERS
300 SOUTH RIVERSIDE PLAZA, SUITE 1650
CHICAGO, IL 60606 | 312.930.2230 | MEPCINC.COM | [LinkedIn]
CELEBRATING OVER THIRTY YEARS IN BUSINESS
Hi Balaji,
It's possible that there will be some heating occurring in the core zones of the Baseline model related to the requirements having a supply air temperature reset of only 5 degrees F or a minimum flow of 0.4 cfm/sf or 30% for 90.1-2007 and 90.1-2010 respectively. Also, check that the sizing ratio in the Baseline systems are at 1.0, sometimes this is increased to oversize the coils instead of the cool sizing ratio and heat sizing ratio values. Note that the sizing ratio also oversizes the Baseline airflow which is not allowed by Appendix G.
For the reheat part of the question, note that the Baseline VAV system should have a zone heating coil but not a main heating coil (i.e. Heat Source set to Not Installed and Zone Heat Source set to Hot Water Loop) then the Reheat Delta T should be equal to the required heating supply air temperature (20 degrees above heating setpoint) minus the required cooling supply air temperature (20 degress below the cooling setpoint).
In terms of whether the correct system type is selected for the baseline model, I'm not sure whether you are asking if the correct eQUEST system type is used for the Baseline System Type of either 5 or 7 or if you want confirmation that the correct Baseline System Type is selected. If Baseline System type is 5, then use Packaged Variable Air Volume in eQUEST. If Baseline System type is 7, then use Variable Air Volume in eQUEST. I would need to know more about the building and Proposed heating fuel source to determine which Baseline System type should be used.
Alex Chapin EIT, BEMP, LEED AP BD+C, O+M
Energy Engineer | Mason & Hanger
A Day & Zimmermann Company
D 804.521.7072 | O 804.285.4171 | F 804.217.8520
4880 Sadler Road, Suite 300 | Glen Allen, VA 23060
masonandhanger.com
Building a More Secure World