We have a proposed LEED Silver office building under LEED 2009 for Commercial Interiors. The intention is to follow NBI Advanced Buildings Core Performance Guide for EA Credit 1.3 Optimize Energy Performance-HVAC. Our stumbling block is an air-cooled chiller that was added for the computer room air handling units in the tenant fit-out. The chiller is a McQuay Pathfinder, Air-Cooled Rotary Screw Chiller with VFD. The capacity is 272 tons. The NBI guide requires compliance with both full load (1.2 kw/ton) and IPLV (1.0 kw/ton).
My chiller is 1.5 kw/ton full load and 0.68 kw/ton IPLV. So it’s a bust at full load. Even at 75% part load I’m already down to 0.8 kw/ton.
It appears the NBI guide doesn’t give consideration for VFD machine until your’e up into a centrifugal water cooled.
So I’m left concluding that my vfd chiller cant even meet their requirements of a standard air-cooled.
The other rub on the design is a 105 degree ambient. When running the machine selection at standard design, 95% capacity gets the 272 tons required with a 10.3 EER. Unfortunately the full load capacity of the machine at standard design conditions is 288 tons at and EER of 9.6.
Has anyone run into this situation in the past and had a successful credit?