Hi BLDG-SIM Users,
We are working on a new LEED Office/Retail Project that intends to use the
Existing District Cooling System (Cooling Towers) for cooling. The proposed
building will have water cooled self contained units rejecting the heat to
the condenser water from the District Cooling Towers.
Based on the document from USGBC "Treatment of District or Campus Thermal
Energy in LEED 2009", we are looking into modeling this as Option 1 -
Building Stand Alone Scenario, where we disregard all the upstream
equipment energy. In the proposed building, this only constitutes for the
HEAT REJECTION on the towers.
However, our system type in Baseline comes out to be System 6 which is
changed to System 8 using the Table 3 in LEED Manual mentioned earlier.
System 8 is VAV with Reheat with cooling energy associated with Chillers
and Cooling towers. Also, we are to disregard the Purchased Cooling from
both baseline and proposed to keep the model DES neutral.
1. Does Chillers, Chilled Water Pumps, Condenser Water Pumps, and Cooling
Towers modeled in the Baseline need to be all considered as part of the
Purchased cooling and thus excluded from the Savings calculations?
2. If we have a Condenser water booster pump for the new building in the
proposed building, should we also model a condenser water pump for the new
building at 19 W/GPM (ASHRAE 90.1) for baseline and include both of them
as part of the downstream equipment energy?
Your help is very appreciated.
Thanks and we look forward to your suggestions.
--
Thanks
Sincerely,
Amit Bhansali, BEMP
Hi Amit,
As per the guidance for district or campus thermal energy in LEED mentioned
that:
*"In Option 1, the energy model?s scope accounts for only downstream
equipment. *This scenario is modeled in accordance with ASHRAE 90.1
Appendix G requirements with the following exceptions:
- The energy source is modeled as purchased energy in both the Proposed
and Baseline buildings for all air handlers, fan-coil units, and other
downstream equipment serviced by district or campus energy systems .....
- Where necessary, building Baseline HVAC system types from Tables
G3.1.A and G3.1.B are modified to be consistent with the purchased energy
source (Table 3) .... "
So, only downstream equipment shall be modeled in both the proposed and
baseline buildings and Chillers, Chilled Water Pumps, Condenser Water
Pumps, and Cooling Towers (upstream equipment) shall NOT be modeled in
option 1.
If the condenser water pump is part of the LEED building and downstream to
DES, shall be modeled as per ASHRAE 90.1 Appendix G. If CW pump upstream of
the building even it's a bosster shall not be modeled and considered as a
part of DES.
Hope that help!
Regards,
Wahid H. Mohamed, LEED AP BD+C