Dear friends,
I am doing an energy model and getting few unmet hours in heating. The air
side system type is a Variable Air Volume and electric heating at system as
well as at zone level. The water side is water cooled chillers with VFD
secondary pumping.
If I change the system type from VAV to Reheat Fan system, the unmet hours
are gone but the model shows huge space heating consumption, which is not
acceptable as per the location of the building. The building is located in
New Delhi (India).
I have tried everything possible to either remove the unmet hours or the
space heating consumption but one goes and the other one comes.
Is there any way to remove unmet heating hours and the space heating
consumption simultaneously? I have used New Delhi weather file.
Anyone please help me out to resolve the problem.
Thanks in advance.
Regards,
Neeraj Arora
Neeraj,
There are many adjustments you can make to address the performance of your VAV system in eQUEST. You didn't describe how many unmet hours you have or what you have tried already. Unmet heating hours can result from underheating, but also from overcooling. Depending on what you change in the model, you might end up increasing your heating energy, or you can end up reducing both cooling and heating energy. Here are a few things to try:
? Enter a value for the system REHEAT-DELTA-T. Leaving this blank can result in thousands of unmet heating hours.
? Set the system COOL-CONTROL to something other than CONSTANT, provided the system you are modeling has the controls capability. I have had success with WARMEST and RESET.
? If you change COOL-CONTROL to COLDEST or WARMEST, increase the zone THROTTLING-RANGE from the default 2?R (2?F). 4?-6? is recommended. You can start with 3? and increase by 0.5? to see how the unmet hours change. If you are comparing two models or two system types, keep the same throttling range in both models to make it a fair comparison.
? Adjust air flow rates, such as your system and/or zonal MIN-FLOW-RATIO.
Search the archives here: http://lists.onebuilding.org/pipermail/equest-users-onebuilding.org/
You could always post your .inp and .pd2 files and someone might look at your model.
Regards,
Bill
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