Controls

By Ben Kincaid, Hydronic Application Specialist, Fluid & Thermal Systems, Indianapolis, Ind.

My first thought was, "What is Durkin smoking?" My second thought was, "He talked somebody into letting us build this thing?" Then, I looked at the numbers. The efficiency and the logic were there, although maybe not very apparent at first blush.

Prior to the KVHS project, my company had done five earth-coupled central systems and 20 or so heat-recovery-chiller jobs with DVPE. One of our collaborations won an American Society of Heating, Refrigerating and Air-Conditioning Engineers Technology Award. Although KVHS would be our first project to combine DHRC and Geo-H/C technologies, we were no less confident.

With 25 hydronic lines leaving the boiler room and numerous terminal units, the specifications called for a "cross-connection verification test" to ensure coils were piped correctly. Thanks largely to Scott Perez, field superintendent for D.A. Dodd Inc. of Rolling Prairie, Ind., none was piped incorrectly.

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Start-up and Shakedown

By Kurt Stevens, Commissioning Agent, KB Solutions, Greenwood, Ind., and Johnny Man, Start-up Technician, Fluid & Thermal Systems, Indianapolis, Ind.

A good design contributes greatly to commissioning. On this project, we felt we had reachable performance targets, even though the scope of our involvement did not include participation prior to construction.

A mechanical system is only as good as its operators, and its operators are only as good as their understanding of the system. On the KVHS project, the key people on the school side, Superintendent Krueger and Director of Operations and Maintenance Jim Bachman, were involved every step of the way.

Our approach to commissioning is weighted heavily toward long-term performance and operational efficiency, so start-up commissioning is only the beginning of the process. Our preference is to monitor systems remotely for at least one year. This allows us to track systems through all four seasons and tweak programming and scheduling.

Our window to the system. The Web portal to the central system features excellent graphics and point control with easy Internet access. We have the ability to fine-tune the system on a daily basis. A separate control system, which also is available online, gives us access to the classroom units and air handlers. We perform the same level of scheduling, monitoring, and optimizing we do on the central system. Also, in conjunction with the building-management system, an ongoing program of carbon-dioxide and humidity testing enables us to ensure excellent indoor-air quality (IAQ).

We not only can monitor the system remotely, we can change system operating parameters as though we were in the school's energy center. We also can see changes made to the screens or system controls.

Coordinating the economizers. In conventional HVAC designs, the cheapest source of cooling is outside air, provided the temperature and dew point are not too high. In a system with a DHRC, the cheapest source of cooling is the DHRC--if there is a concurrent need for heat (Table 1). The need for heat could be building heating, domestic water heating, or natatorium water heating. In buildings with variable-air-volume (VAV) and multizone air handlers and spaces with high internal heat loads, such as KVHS, operating dollars can be saved by making the first call for cooling the chilled-water valve, rather than the economizer damper. That means the chilled-water system is available throughout the year, and when air-handling equipment starts, so does the DHRC. The DHRC runs to make 44 F evaporator water and 130 F condenser water. The VAV units operate during winter, just as they do during summer, with outside-air dampers at minimum setting.

"Coordinating the economizers" means creating opportunities for the DHRC to run. It means heating the building with Btu from the lights and occupants. During the course of a normal school day, once KVHS comes off night setback, the DHRC carries the full heating load at all outside-air temperatures above 35 F.

Through commissioning, we learned there were times when the DHRC was fully loaded transferring heat from the chilled-water return to the heating-water return, and yet additional heat was required. The chilled-water return downstream of the DHRC was 52 F. With the Geo-H/C operating at partial capacity to add heat, but extracting heat from the well field, providing a water temperature of 45 F, the control algorithms were modified so that heat was extracted from the building chilled-water return. Along with normal commissioning debugging, the ability to observe system operation at any time led to system-setup improvements tailored to "actual" operation, as opposed to "predicted" operation. We expect the savings of the second year of operation to improve over those of the first.

Schedule, schedule, schedule. Scheduling is one of the most important aspects of the commissioning process. At KVHS, operating schedules took months to refine.

Recommendations for Phase 2. One of our first observations was that the geothermal field was running cooler than expected. An unanticipated benefit of the hybrid-geothermal design is that we are able to adjust operational strategy and still maintain a high level of efficiency.

Phase 2 of the project--renovation of the middle school that shares the campus--will include the addition of two control valves to the system:

• A valve across the two well-field lines that will allow water returning from the field to be tempered.
• A valve allowing well water to be pumped directly through the building. This will enable cooling without any compressors running, as the water in all three systems (heating, cooling, and geothermal) is common.

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Energy Savings

By Bill Orsburn, Director of Business, Kankakee Valley School Corp., Wheatfield, Ind.

The General Fund is the main operating fund for Indiana public schools. At Kankakee Valley, staff salaries and benefits account for approximately 90 percent of General Fund expenditures, with utilities constituting a major portion of the remaining 10 percent. The bottom line is that any money saved on utilities can be redirected to the classroom. Conversely, if utility costs are not kept under control, it is conceivable that teachers and/or classroom programs could have to be cut.

At the start of the project, I was pleased to hear our consultant say he thought the new systems would reduce utility costs by $104,000 a year, even though we were doing several things that might otherwise increase energy use, such as adding cooling to the main gymnasium and auditorium, addressing summer humidity issues, and increasing fresh air into the building.

I have my own way of tracking utility bills and adjusting for the severity of winters and the cost of energy: I look at a running three-year average for all of our buildings. If I adjust high-school consumption by the same increase or decrease the other buildings experienced, I have an accurate picture of what the high school would have used had it not been renovated (Table 2).

The hybrid-geothermal system shifted building heating from gas-fired boilers to heat recovery and geothermal, so I was anticipating a substantial decrease in gas consumption and an increase in electricity consumption. The analysis is somewhat complicated by the fact that our middle school is fed from the same gas meter as the high school.

It is interesting to note that the cost of natural gas has leveled off and even decreased slightly. Last year, we bought at $1.06 a therm, compared with $1.12 the previous year and $1.20 the year before that. The "Katrina effect" was relatively short-lived. On the other hand, the cost of electricity went up 21 percent, which we did not anticipate. Still, we are ahead on our scheduled savings.

Even more important than saving taxpayer dollars has been improving the learning environment for students and teachers at KVHS. Since the renovation, hot/cold complaints have been reduced to almost zero, and there has been a palpable improvement in IAQ.

This was a very successful project.

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References

1) Durkin, T.H. (2006, July). Boiler system efficiency. ASHRAE Journal, pp. 51-57.
2) Durkin, T.H., & Cecil, K.E. (2007, August). Geothermal central system. ASHRAE Journal, pp. 42-43, 47-48.

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