Efficiency with the AquaEdge® 23XRV
Carrier’s AquaEdge® 23XRV is the world’s first water-cooled variable speed screw chiller. The 23XRV combines the reliability of a screw compressor with the energy savings of a variable frequency drive (VFD).
Lowest Life Cycle Chiller
A multi-use facility near downtown Las Vegas, Cashman Center boasts exhibit space, meeting rooms, a theatre, parking, and a baseball stadium. Built in 1983, the facility’s original chillers were over 25 years old and had become inefficient and costly. Instead of building new, the owners chose to maintain the facility and focus on how to improve facility energy savings.
The Strength of SPLV
Because of its simple, speed-optimizing operation, 23XRV chillers deliver balanced efficiency across a wide range of conditions, which can help earn LEED credits in the energy and atmosphere category.
How to Stage Chillers
The most common way to stage a multiple chiller plant is with a sequenced chilled water staging arrangement.
If the building is started at maximum capacity, all 3 chillers and the building are at 100% load.
Both the building and chillers unload to 67% and a chiller can now be shut off.
After shutting off 1 chiller, the other 2 can be loaded to 100%. The building load is still at 67%, meaning that the condenser temperatures will not be at design conditions.
As the building further unloads, the remaining 2 chillers will be unloaded to 50% and the building load reaches 33%.
Another chiller can be shut off, and load the remaining chiller to 100%. The building load is still at 33%.
The remaining chiller is unloaded to 0% building load.
Any place where the chillers operate at 87.5% or higher is 100% load bin.
Any place where the chillers operate between 62.5% and 87.5% is 75% load bin.
Any place where the chillers operate between 37.5% and 62.5% is 50% load bin.
After taking into consideration the total number of chillers, the operating hours, building load profile and geographic location, the system part load value (SPLV) for this specific application is different than a standard IPLV.
In constant primary flow systems, the delta T across a chiller's evaporator is directly proportional to load.
If the base load machine was designed to operate at 40°F, it would have been >10% worse in efficiency.
Maximize Efficiency with Series Counterflow (SCF)
In a series counterflow arrangement, the work done (lift) by each compressor is reduced, which significantly improves the efficiency of the chillers at full and part load conditions.