Last week I went to another facility to check out a Carrier 19XL that had been converted to variable speed with a York VFD, and PIC panel replaced with York Optiview. Local JCI did retrofit. Rep pointed out mods to allow entering condenser water temp (ECWT) down to 55°F during low load operation to save $$ and would not create oil return problems. Said VFD capability only partially responsible for energy reduction realization, that lowering ECWT during part load operation is other vital component to reduce $$.
Talked to chief engineer of facility and he seems pleased with conversion. Has seen operating costs go down and is expecting about a three year payback on the conversion. I was impressed with the Optiview panel, a light year ahead of the PIC II panels on my 19XR machines as far as ease of use and presentation of vital info goes.
We have been considering various energy optimization strategies or one of our 19XR chillers (and central plant) for some time, now. We've entertained options for a Carrier VFD conversion (essentially turning our 19XR into a 19XRV) to outright replacing the chiller with a reduced tonnage York YK VFD or McQuay w/Turbocor (oil free) machine. While the Turbocor option seems quite inviting, our existing 19XRs are just nine years old. To rip out a machine with approx. 25k operating hours logged seems a waste if effective VFD conversions are available that render decent payback schedules. Since our plant operates 24/7/365, part load operation with our present constant speed machines is a killer, with chiller kw per ton often exceeding 1.0 (chiller motor amps alone, not counting pump and tower energy use).
Would appreciate any feedback from folks in our new chiller forum concerning constant speed chillers converted to VFD, and how effective such are in real time for reducing overhead.