Spring 2014 Forum
Keepin’ It Cool, How to Get The Most Out of Your Chilled Water Plant
March 7, 2014
United Association of Plumbers and Steamfitters Local 290 Union Hall and Training Center, Portland
The Oregon APEM 2014 Spring Forum, “Keepin’ It Cool, How to Get the Most Out of Your Chilled Water Plant” on March 7, 2014 was a huge success. The forum was held at United Association of Plumbers and Steamfitters Local 290 Union Hall and Training Center. The day was kicked off by Greg Nelson who gave us an introduction to Chiller terms, vocabulary and some basics about mechanical cooling. He discussed the differences between air cooled systems and water cooled systems. Greg then went on to discuss the difference between scroll chillers, screw chillers, and centrifugal chillers and the different capacity and chiller efficiency associated with each system for both air cool and water cooled systems. After discussing some key differences between air-cooled and water-cooled systems for decision-making purposes, Greg finished his presentation by highlighting primary and secondary pump efficiencies.
We then heard from a panel of speakers starting with Henry Verde, a representative from Carrier, who gave us a quick look at Carrier’s interactive “Building System Optimizer”. By choosing a building type, location, system performance level, and other variables, Carrier’s program compares two different system options side by side. This program can be useful for anyone looking to purchase a new system or replace an existing system. It gives a company the opportunity to evaluate specific chillers relative to their unique environment.
Daniel Driver, a representative of Oregon Trane, discussed in more detail the differences between air-cooled and water-cooled systems and the expense involved with installing a new system or retrofitting an old system. Daniel recommended looking for the “Sweet spots” for a system between highest efficiency and low initial costs. The price for the chiller is not the only cost that should be considered. In some cases additional piping, a new mechanical room, or controls for tower/pump/refrigerant monitoring may need to be added for the system to work properly.
Anthony Tomasi, a representative from Johnson Controls discussed basic types of “packaged” chillers available today and their most common applications, recent advancements in technology, rough idea of costs vs. efficiencies, and most common chiller system pitfalls.
We wrapped up the panel with Michael Wilson, a representative from McQuay, who talked about magnetic bearing chillers. Magnetic bearing chillers minimize efficiency losses and mechanical complexity inherent to traditional centrifugal chillers. Magnetic bearings have less than 0.2% the friction losses compared to conventional roller or ball bearing designs. The rotor shaft is held in position with electromagnetic cushions. These continually change in field strength to keep the shaft centrally positioned. The shaft’s position is monitored by ten sensor coils whose signals are fed back to a digital controller
After the panel Doug Hansberry discussed chiller plant efficiency, with a focus on CW and CHW temperature reset, centrifugal chiller adjustable frequency drivers (AFDs), and variable primary pumping (VPP). He explained that these are three means for improving energy efficiency in water cooled chiller plants: adjustable frequency drives (AFDs) on chiller compressor motors, condenser water temperature reset, and variable primary flow. But are the savings claimed by the manufacturers really true? How cold can you run the condenser water system before running into problems? How is the condenser water system temperature controlled? How do you retrofit a fixed primary system to variable flow and how is it controlled? Do the economics work? Doug Hansberry discussed the results of retrofitting these technologies to a very large chiller plant at a large semiconductor facility. Decreasing CW temperature eliminates wasted work done by the compressor. This strategy can be applied to existing plants.
After lunch Don Snodgrass briefly discussed chiller maintenance. Don explained that the amount of time spent on each machine makes a big difference on the machines overall efficiency. In order to get the most out of your chiller you should be spending the proper time maintaining the machine. Some basic steps that can help maximize efficiency are, stay on top of maintenance, cleaning tubes annually, and oil analysis.
Jerry Bogorad, the Director of Facility Operations at OMSI provided a brief history of OMSI and background regarding recent chiller upgrade. His presentation included a time lapse video of the old chiller being removed and the new chiller being lowered into the mechanical room.
Peter Mobery, gave us an overview of the OMSI Chiller upgrade. The areas of focus were energy modeling, engineering design, and commissioning. The analyses process was fieldwork, creating building geometry, modeling systems, creating schedules, and calibrating models. The original system was a 205 ton heat recovery chiller, 2,480 MBH heating capacity, and a 500 ton cooling only chiller capacity with standard efficiency boilers (7000 MBH). The heat recovery chiller made hot water from 90°F up to 130°F depending on outside air temperature and available cooling load. The conservation measures evaluated in this project were to replace the chiller, separate the chiller from projector room, replace data room air conditioner, replace pneumatic controls with DDC, add VFDs to AHUs, add airside economizers, and add CO2 DCV to AHUs. The results of this analysis was that the energy saving were not as high as expected, and initially showed payback of less than ten years.
Lyn Schmidt from the Energy Trust discussed the role incentives played in the project at OMSI and gave a brief overview of potential support the Energy Trust could provide for other projects.
Mike Wilson, wrapped up the OMSI discussion by comparing the old OMSI chillers with the new equipment that was installed. OMSI had a McQuay heat recovery chiller nominal 200 ton and a McQuay Centrifugal nominal 500 ton. These were replaced with a McQuay Templifier chiller nominal 190 ton (the purpose was to reduce gas demand from the boilers) and a Daikin/McQuay magnetic bearing centrifugal nominal 550 ton. The problem with these machines is that the centrifugal would not unload, the heat recovery was beating itself to death, the control system could not optimize, and they could not install air side economizers. OMSI now saves energy because the centrifugal chiller now has superior part load to 15%, the heat recovery has more compressors in the chiller, control system now optimizes chiller changeover, and the boilers are tuned and more efficient. Some other benefits to this upgrade was magnetic bearings use no oil or oil management. Efficiency will remain consistent since there is no oil, and very low maintenance.
In addition to having many wonderful speakers also had a chance to talk to multiple chiller manufacturer’s representatives and vendors for chilled water system components during multiple networking breaks.