We are working on a project where the total project has five towers on one podium. We are certifying only one tower for LEED-NC with an area of 34152 sq.m. and hence the baseline system as per ASHRAE 90.1 2007 is system 8.
As per actual design the entire project has an HVAC system consisting of four chiller with each 1000TR capacity.
Since we have the heat load sheet for the entire system but not separately for the tower which is to be certified. So what should be the Chiller capacity and type that I consider in System Modeling for baseline energy simulation.
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Marcus Sheffer
LEED Fellow7group / Energy Opportunities
LEEDuser Expert
5909 thumbs up
August 23, 2013 - 9:05 am
The Baseline is the easy part. Auto-size the cooling load, add 15% (G3.1.2.2) and based on that capacity select the chiller number and type from Table G3.1.3.7.
Poorva Keskar
3 thumbs up
August 26, 2013 - 2:12 am
Thank you, for reply!
We have done this for baseline and our chiller capacity is 600TR. But as project has four chillers which are simultaneously used for five tower, so shall I considered 600TR for design-case too? or I should go for 1000TR (as per actual design of individual chiller) though it is designed for multiple towers.
Marcus Sheffer
LEED Fellow7group / Energy Opportunities
LEEDuser Expert
5909 thumbs up
August 26, 2013 - 9:18 am
Sounds like you really have a central plant that could perhaps be treated as a district energy system. See the Treatment of District or Campus Thermal Energy in LEED v2 and LEED 2009 - Design & Construction (DES v2) dated August 10, 2010 which can be accessed at: https://new.usgbc.org/resources/des-district-energy-systems-guidance-v22
Neither of the sizes you mention would be correct. You almost always model the proposed case as designed. Assuming the loads are identical in each tower the proposed chiller capacity works out to 800TR for one tower.
Tracy Black
Professional Engineering ConsultantEngineered Solutions
August 27, 2013 - 9:47 pm
I think that Marcus is correct that you may want to conside the model for a district system, rather than a central plant type system.
One item that is conspicuously absent from this conversation is the details of the actual chiller. Chillers have their own maximum efficiency points and that is usually in the range of 75% load to 85% load depending on a host of other factors. It is not usual that one chiller supports multiple towers because the delta-T across the tower is more or less fixed depending on the weather conditions and if you are running a glychol mixture or just water with inhibitors. Most facilities run only water for environmental safety.