My question is regarding the following procedure as outlined in Trace 700 help:
"To determine which ASHRAE baseline system to model, refer to ASHRAE Standard 90.1-2007, Table G3.1.1A (below). You will need the following information to make a proper system selection:
Building type (residential or non-residential)
Building square footage (available on the Building Areas Report)
Number of floors
Building heating source
Here is my QUESTION:
Background - My project is a large data center (all electric heating) that is over 150,000 SF. It is being modeled as New Building C&S. I need to divide up my systems to smaller systems mainly because of the functions of each room or zone and load density (number of floors, data rooms vs. offices vs. support areas, etc.). Per Appendix G, TABLE G3.1.1A: Baseline System Types, I have to use system 8 (VAV with PFP Boxes).
It is not clear to me if the system selection is still based on the TOTAL BUILDING area or based the smaller areas of each system.
Do I still use system 8 for each sub-systems (single zone or group of zones that form the sub-systems) ... or do I have the option to use other systems. and if so what is the criteria?
Thanks,
Marcus Sheffer
LEED Fellow7group / Energy Opportunities
LEEDuser Expert
5916 thumbs up
June 19, 2014 - 8:32 pm
You have to use a single baseline system type unless one of the exceptions under G3.1.1 applies.
If one or more applies then you use the predominant condition (largest area) to model the G3.1.1A system type. If you are applying exceptions the area that they cover is subtracted from the total and this may change your baseline system type. For example, if your predominant condition is only 145,000 sf then you would model a system 6.
Mark Stromberg
June 20, 2014 - 2:53 pm
Thanks Marcus for your quick response.
I would like to confirm what should be the systems in our building when it is divided to different systems. It is approximately 185,000 SF. The overall predominant spaces are computer server rooms, approximately 112,000 SF. And the rest is MEP spaces, offices and support areas. By the time we divide up the systems by floors (37,000 SF each) and set up the systems based on the exceptions, some system may be less than 25,000 SF. This is especially worst because we have to divide up the systems by floor. Therefore, no predominant space would be even close to 150,000 SF. Does this mean we have to use packaged units (System 4 and 6) for all the systems?
Thanks
Marcus Sheffer
LEED Fellow7group / Energy Opportunities
LEEDuser Expert
5916 thumbs up
June 20, 2014 - 12:58 pm
Sounds like the predominant area results in a system 6. You do not determine this per floor, but by overall area. Don't confuse system type with the quantity of systems.
What exception applies to the other spaces? Does not sound like "a" applies. Maybe "b"? You should be sure to state which exception applies and why it applies in order to use it.
Mark Stromberg
June 20, 2014 - 2:07 pm
Marcus
The exception is primarily based on “peak thermal loads that differ by 10 Btu/h⋅ft2”. There MEP spaces differ in cooling from the other support spaces and offices. So we have at least 2 systems on the typical floors and multiple systems in the lower level where most of the MEP equipment is. Plus, we also have stairways and elevator shafts.
So the building can be divided into at least 10 (minimum) and up to 15 or 16 if we need to keep systems separate based on thermal load.
With this arrangement, I assume for all electric building we have to use System 6 (or is it 8?) as the predominant system for the computer server rooms, and for the rest of all other spaces use system 4. Am I correct with my assessment?
The way I read the exceptions “a” and “b”, it directs energy modelers to use only system 4 for the non-dominant systems. It does not allow for the same system (6 or 8) be repeated. We cannot have multiple systems of 8 (or 6) in the same energy model. Am I interpreting this correctly?
By the way, should the single stairway shaft and an elevator shaft (rising thru. multiple floors) be separate systems on their own or can each be part of one of the floors, say 1st floor or top floor)?
Thanks,
Marcus Sheffer
LEED Fellow7group / Energy Opportunities
LEEDuser Expert
5916 thumbs up
June 20, 2014 - 2:30 pm
It is a system 6 if the predominant area is under 150,000 sf. Following exception b the remaining areas are a system 4, so you sre correct as far as I can tell. You are correct about using the system 4 and not repeating the 6 or 8.
The elevator shaft I assume is not directly conditioned so it does not get a system at all. How are the stairs conditioned? Heating only can be a system 9 or 10 and separate. If fully conditioned then it gets included with the system per floor.
Mark Stromberg
July 2, 2014 - 12:39 pm
Hi,
Another question,
If I have five(5) systems type 4 (single zone HP) each with a different cooling capacity, do I need to create separate cooling plants for each system with the cooling plant EER in the capacity range matching the system OR can I add up capacity all the five(5) systems and assign all of them to a single cooling plant with an EER in the capacity range of the total of all five (5) units.
Marcus Sheffer
LEED Fellow7group / Energy Opportunities
LEEDuser Expert
5916 thumbs up
July 2, 2014 - 12:57 pm
Separate
Mark Stromberg
July 8, 2014 - 6:47 pm
Another question,
The project is a phased construction. During the first phase, only a portion of the building will be built. Rest of the area even though has been planned and conceptualized, but has not designed (mechanical schedules, etc are not prepared) While going for LEED energy modeling, we are considering the whole building - including the future space. How would we provide information of the systems in Supplemental Table 1.4 for various Future AHUs, Fan Coil units, since they are not in the mechanical schedules? On the other hand since baseline system is all hypothetical, we can provide information of the complete baseline building system (Modeling Output results).
Marcus Sheffer
LEED Fellow7group / Energy Opportunities
LEEDuser Expert
5916 thumbs up
July 8, 2014 - 9:39 pm
For areas that do not have any of the systems designed you model them identical to the Baseline systems. You can claim savings for any requirements in the tenant lease agreement.