Chilled Water Systems

 

General

The purpose of this report is to develop a brief analysis of the existing chilled water system at the Salt Lake Community College Taylorsville Redwood, South City, and Jordan Campuses. The result of this portion of the analysis will be as follows:

  1. Determine current campus chilled water loads
  2. Project future campus chilled water loads
  3. Determine whether or not the main chilled water piping is sized adequately enough to handle the future loads
  4. Recommendations regarding the campus chilled water capacity and main line sizing

This report will facilitate in providing a basis for planning, funding, and implementation for future years; however this is not a utility master plan. The report is predicated on the need to provide continued reliable service to existing campus buildings and to determine whether or not the existing infrastructure will be able to support facilities as the campus expands.

Scope of Work

This report analyzes the existing and future campus chilled water needs and the main chilled water pipe sizing.

  • The key items undertaken by this study include:
  • Review of existing campus chilled water demand
  • Review of existing chiller and main piping capacities
  • Utilizing the architectural master plan data (provided by AJC), determine future campus chilled water requirements
  • Determine whether or not the current cooling capacities can support the projected campus growth
  • Recommendations

Ancillary equipment associated with the chiller (i.e. pumps, valves, etc.) will not be included in this report. However, it should be noted that if the overall cooling requirements increases, all ancillary equipment will be required to be analyzed for capacity. Additionally, the chilled water distribution system will not be included in this report, but as in the case of the ancillary chiller equipment, distribution piping and associated equipment will be required to be scrutinized as campus cooling requirements are increased.

Conceptual Cost Estimates

Conceptual cost estimates will not be included in this report, but is highly recommended when performing the in depth utility master plan in the future.

Existing Campus Cooling Loads

The Taylorsville Redwood campus chilled water system is comprised of seven chillers interconnected into an east and west loop. With this type of arrangement, in the event of a chiller going offline does not detrimentally affect the system due to the redundant chillers. The chillers serving the east loop can be seen in Table 2-1 and those chillers associated with the west loop are depicted in Table 2-2. Additionally, the ATC and Auto Trades buildings each have their own chillers which are not connected to either loop. These chillers will not be included in the overall campus chilled water analysis.

Table 2-1: Existing Chiller Capacities – Taylorsville Redwood Campus East Loop

Chiller Number Capacity (Ton) Install Date Manufacturer
1 700 2003 Carrier
2 700 1998 Carrier
3 500 2006 Carrier

Note: East loop main chilled water line = 10”, delta T = 7 F

Table 2-2: Existing Chiller Capacities – Taylorsville Redwood Campus West Loop

Bldg Name Capacity (Ton) Install Date Manufacturer
S & I 500 1995 Carrier
LAC #1 300 1993 McQuay
LAC #2 300 1993 McQuay
Library 200 2002 Trane

Note: West loop main chilled water line = 8”, delta T = 7 F

The South City campus chilled water loop is comprised of three chillers which are shown in Table 2-3. As in the Redwood campus, redundancy is achieved through the interconnection of all three chillers.

Table 2-3: Existing Chiller Capacities – South City Campus

Chiller Number Capacity (Ton) Install Date Manufacturer
1 300 1990 Trane
2 300 1990 Trane
3 130 1994 Trane

Note: Main chilled water line = 10”, delta T = 5 F

The Jordan campus is currently being served by four chillers located throughout campus within building mechanical rooms. As in the case of the other two campuses, redundancy within the system is achieved through the interconnection of the four chillers. Table 2-4 depicts the existing chiller information.

Table 2-4: Existing Chiller Capacities – Jordan Campus

Chiller Number Capacity (Ton) Install Date Manufacturer
1 53 1999 Carrier
2 250 1999 Carrier
3 500 1999 Carrier
4 800 2007 Carrier

Note: Main chilled water line = 12”, delta T = 10 F

The campus chilled water system capacity was determined by summing all of the operational chillers and subtracting out the largest chiller. This new value is called firm capacity and allows for redundancy within the system. Existing campus chilled water loads were determined based on gross square footage of the served buildings, a value of 300 SF/Ton, and the average delta T experienced by each campus. The results are as follows:

Table 2-5: Existing Campus Chilled Water Loads Based on Gross Square Footage

Campus Gross Area (SF) SF/Ton Total Campus Chilled Water Load (Ton) Chilled Water Firm Capacity (Ton) Chilled Water Flow Rate (gpm)
Taylorsville Redwood East Loop 521,633 300 1,739 1,200 5,962
Taylorsville Redwood West Loop 357,637 300 1,192 800 4,087
South City 346,247 300 1,154 430 5,540
Jordan 250,294 300 854 803 2,002

 

Table 2-6: Existing Campus Chilled Water Distribution Analysis

Campus Chilled Water Flow Rate (gpm) Main Pipe Size (in) Flow Velocity (ft/sec) Heat Loss (ft/100ft)
Taylorsville Redwood East Loop 5,962 10” 22.4 13.3
Taylorsville Redwood West Loop 4,087 8” 26.3 23.9
South City 5,540 10” 22.6 13.5
Jordan 2,002 12” 5.73 0.769

Note: Flow velocity and head loss values were determined by interpolation using information from the Cameron Hydraulic Data Eighteenth Edition.

Based on the assumed value of 300 SF/Ton, it appears that the chilled water mains for the Taylorsville Redwood and South City campuses are well undersized. Typical industry standards for pipe sizes up to 10” require a head loss of no more than 4’ per 100’ of pipe. On the other hand, the Jordan Campus appears to be sized adequately and both the flow velocity and head loss values are well within industry standards for 12” steel pipe.

Future Campus Chilled Water Loads

As in determining the existing loads, the future cooling loads were projected by assuming a value of 300 SF/Ton and utilizing the architectural master plan which identifies the new buildings and layout planned for the campus. The estimated growth is as follows:

Table 2-7: Future Campus Chilled Water Loads Based on Gross Square Footage

Campus Gross Area (SF) SF/Ton Additional Campus Chilled Water Load (Ton) Total Future Campus Chilled Water Load (Ton) Total Future Campus Chilled Water Flow (gpm)
Taylorsville Redwood East Loop 225,000 300 750 2,489 8,533
Taylorsville Redwood West Loop 225,000 300 750 1,942 6,659
South City 200,000 300 667 1,821 8,740
Jordan 600,000 300 2,000 2,834 6,802

Note: For the Taylorsville Redwood Campus, it is uncertain to which loop the future 225,000 GSF campus area will be added. The analysis will look at both loops experiencing the growth.

Based on the projected growth of the campus, the new campus chilled water requirements will be the following:

Table 2-8: Future Chilled Water Requirements

Campus Existing Firm Capacity (Ton) Future Campus Load (Ton) Existing Main Chilled Water Pipe Size (inches) Future Main Chilled Water Pipe Size (inches)
Taylorsville Redwood East Loop 1,200 2,489 10” 24”
Taylorsville Redwood West Loop 808 1,942 8” 20”
South City 430 1,821 10” 24”
Jordan 803 2,834 12” 20”

 

Recommendations

In order for the campus to continue to provide adequate and reliable chilled water to its building users, the following needs to occur:

  1. The continuance of interconnecting the chillers is necessary.
  2. The Taylorsville Redwood and South City Campuses appear to be exceeding capacity on their existing distribution network. It is recommended to determine more accurate building cooling loads associated with the chilled water distribution system in order to determine accurate flow rates.
  3. Consider increasing the delta T of the chilled water distribution system. Increasing the delta T will decrease flow and as a result will decrease pumping and piping costs. It is not uncommon to see delta T in the 12-18º F range.
  4. Verify location of 2-way and 3-way valves. 2-way valves should be utilized near the chiller and 3-way valves should be used for the extremities of the campus. This will increase the overall system delta T which is directly related to energy savings. Further detail analysis is required for this item.
  5. Consider the addition of the ATC and Auto Trades buildings into the existing Redwood campus chilled water loop.
  6. Overall chilled water firm capacity needs to increase to match the projected chilled water load for each campus.
  7. Main chilled water line needs to increase as shown in Table 2-8.
  8. Perform block load on existing buildings to determine actual cooling requirements.
  9. Develop chilled water hydraulic model.
  10. Develop a utility master plan including capital improvement priorities.