I have a small project where the existing system in a 10 story building is a water source heat pump system. From what I gather, this type of system is not very friendly towards achieving LEED CI Credit 1.3 - Option 1 for a few reasons.
First is that the CPG requires that part load calculations must be performed and the system explained on how it will achieve efficient operation at these part load conditions, which a water source heat pump can not really do (it just cycles the compressors on and off, and the building water pumping system is constant volume as well...). The only piece of equipment in the system that can operate differently at part load is the fluid coolers which are provided with VFDs.
Second, the whole issue about active controls in private offices and special occupancies to modulate the HVAC system... I take this to mean that one heat pump unit would be required for each individual office and conference room etc... but once again a heat pump unit does not modulate, it just turns the compressors on and off while maintaining 100% supply airflow. Can anything else modulate, such as the outdoor air to each unit? Unfortunately this would not save any energy either since the building outdoor air loop is a preconditioned constant volume system...
Based on my assessment, the only way to achieve any points within this credit would be to attempt the performance approach, which still may not yield the results I want. Does anybody else agree with my interpretation of this credit when applying a WSHP system, or am I missing something?
Paul Conrad
Energy EngineerCLEAResult Consulting
346 thumbs up
September 8, 2010 - 11:27 am
Jonathon,
I hate to say it, but I agree with your interpretation. WSHP's may not be a good option for this credit, at least for the prescriptive option.