Summer cooling savings guidebook

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Summer cooling savings guidebook

Increase proﬁ ts while sustaining comfort

A guidebook of tips and ideas to help your business save on summer cooling bills

MN

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Take action to lower your summer energy bills

With rising energy prices making headlines from gas pumps to energy policy, now more than ever taking steps to lower your energy bills can lead to fast paybacks and signiﬁ cant long-term energy savings.

This guidebook offers tips and upgrade suggestions for lowering your summer energy bills with a focus on cooling savings.

You can easily implement some of these low- to no-cost tips and see almost immediate payback. Other suggestions involve capital improvements with longer paybacks that still can make sense for many businesses.

HVAC offers large opportunities for

energy savings

Heating, ventilating and air conditioning (HVAC) systems account for 39 percent or more of the electric energy used in commercial buildings in the United States. Consequently, almost every business has the potential to realize signiﬁ cant savings by improving its control of HVAC operations and improving the efﬁ ciency of the systems

HOW CAN CONSERVATION IMPROVE YOUR PROFITS?

Taking action to lower your cooling bills leads to immediate and long-term proﬁ ts for your company. When you lower operating costs, such as energy bills, the money you otherwise would have spent stays in your business. The chart below can help you ﬁ gure how much more you’d have to sell to have a similar bottom-line impact for your company.

For example, if your actions save $1,000 on annual energy bills and your sales proﬁ t margin is 10 percent, the impact to your bottom line is the same as an additional $10,000 in sales each year. With rapidly rising energy prices the trend across the nation, conservation also can offset rising energy prices that otherwise could eat away your proﬁ ts.

ANNUAL COST SAVINGS

FOR THE MEASURE PROFIT AS A PERCENTAGE OF SALES

2% 5% 10% 20% $10 $500 $200 $100 $50 $100 $5,000 $2,000 $1,000 $500 $1,000 $50,000 $20,000 $10,000 $5,000 $10,000 $500,000 $200,000 $100,000 $50,000 $100,000 $5,000,000 $2,000,000 $1,000,000 $500,000

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it uses through proper design, installation and scheduled maintenance.

For any type of system, following these steps will lead to energy savings. Estimate your savings by conducting a heating and cooling survey and working with an engineer (on-staff or consul-tant) to calculate savings potential.

1. Rightsize your cooling system to take advantage of load reductions

2. Eliminate CFC refrigerants from your system through retroﬁ t or replacement

3. Systems older than 10 to 15 years offer an investment opportunity. Install new high-efﬁ ciency equipment to reduce operating costs and match equipment size to cooling load

4. Implement cooling system efﬁ ciency strategies such as free cooling

Cooling systems consist of various components that must work together to operate at high-est efﬁ ciency while ensuring proper occupant comfort. Improvements to any system must, of course, incorporate improvements to its individual pieces of equipment.

However, these changes must be viewed as part of an integrated system approach. To improve your building’s overall efﬁ ciency, modiﬁ cations in the design or operation of one set of compo-nents will affect the operation of other equipment within the system.

Which cooling system is right for you?

This chart represents the typical selection of cooling systems for buildings of a given height and ﬂ oor area. (Source: HVAC&R Center – University of Wisconsin Madison)

12 10 8 6 4 2 0

Height (Floors)

Typical Choices of

Air Conditioning System

Water-Cooled Chiller

Modiﬁ ed

Rooftop/ Air-

Cooled

Chillers

Distributed Heat Pumps

Rooftops and Condensing Units

Energy savings in new construction

The best time to build in HVAC and other energy savings for your new addition, major renovation or new facil-ity is early in the design stage.

Energy Design Assistance, by ConservationWise from Xcel EnergySM_{, offers free design} consultations and rebates when you make recommended improvements. Contact your Xcel Energy

account manager or our Business Solutions Center at 1-800-481-4700 to discuss your options before you begin your building design.

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Have more questions? Ready to begin?

Contact your Xcel Energy account manager or our Business Solutions Center at 1-800-481-4700. Sign up for conservation-related e-mails about rebate programs, bonus offers and special events at xcelenergy.com/subscribe Rooftops and condensing units (split systems)

These systems typically are found on buildings three stories or less due to the difﬁ -culty of forcing air down a larger number of stories. This category includes: residential, light commercial ofﬁ ce space, strip malls, big box retail stores, supermarkets and other buildings that are less then 30 feet high but cover large footprints.

Modiﬁ ed rooftops and air-cooled chillers

These are found on larger buildings where either the building height or layout precludes the use of rooftops. A modiﬁ ed rooftop will have larger fans to force the air farther. The air-cooled chiller sends out chilled water to meet the loads, but does not require the use (and maintenance) of a cooling tower.

Distributed heat pumps

These are often found in large, upscale hotels and ofﬁ ce buildings that have multiple tenants. This category includes water-source heat pumps and some air-source heat pumps. This arrangement allows individual control and metering of spaces. Water-cooled chillers

These are typically used in large buildings where a large amount of cooling is neces-sary. This system allows chilled water to be efﬁ ciently pumped around the building to air handlers, which meet the cooling needs.

Rightsizing your system

Rightsizing your system ensures that your system capacity is well matched to your facility’s needs. As buildings age, leaky ducts, inefﬁ cient operation or additional ofﬁ ce

TIPS FOR CHOOSING A NEW COOLING SYSTEM

• Proper sizing is critical to efﬁ cient performance

• Choose equipment that saves energy in the long term and qualiﬁ es for Xcel Energy conservation rebates

• When buying properly sized heating/cooling equipment, look for the ENERGY STAR®

label – your guarantee of savings

• Ask the contractor if he or she is a member of a national professional trade organiza-tion such as the Air Condiorganiza-tioning Contractors of America (ACCA). Such afﬁ liaorganiza-tions demonstrate that contractors have access to the latest technical information regarding HVAC systems, and make quality an integral part of their company operations

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equipment or staff can make a previously appropriate cooling system undersized. Likewise, efﬁ ciency improvements to lighting, building envelope or other systems can make a building’s current system oversized.

To prepare to rightsize your heating and cooling systems, compile basic information and mea-surements about the systems and your facility. Next, calculate the required cooling and heating loads for your building.

To get started, recruit a survey team that could include a building engineer, HVAC technician, boiler operator and electrician. You will need to evaluate your available staff resources and staff capabilities. If you do not have the means of taking these measurements, you may want to contact an independent testing, adjusting and balancing (TAB) ﬁ rm or seek outside engineering services. Before you begin

You will need the following items to complete your survey:

• The latest speciﬁ cations for the heating and cooling equipment in your building • The TAB report for your building’s pumping systems

• “As built” mechanical drawings

• Operations and maintenance manuals for the boiler, chiller or unitary system equipment

• The system logs showing hot- and chilled-water supply and chilled-water return temperatures and ﬂ ow rates (if you have an energy management system)

• A data logger (note: for unitary systems only) • A calculator

Use the evaluation survey provided for your type of cooling system to determine if your cooling system is oversized, undersized or rightsized for your building. For chillers, see page 16 and for packaged or rooftop systems, see page 11.

How much cooling do you need?

Use these numbers as a rule of thumb to determine equipment sized for a given job. Then, adjust the numbers based on extenuating circumstances that may exist. The typical commercial building requires 1 ton of cooling for every 400 square feet. Source: HVAC&R Center – University of Wisconsin Madison

ADVANTAGES OF A RIGHTSIZED SYSTEM

In addition to reducing energy consumption and costs, heating and cooling upgrades will:

• Reduce noise

• Lower ﬁ rst costs for equipment • Reduce equipment footprint • Eliminate CFCs

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If you plan to upgrade any heating or cooling equipment, ﬁ rst implement any other efﬁ ciency upgrades. Earlier up-grades (such as lighting replacements or building construction improvements) may change the size requirements for your new heating or cooling system. Check with our Business Solutions Center at 1-800-481-4700 to determine if equipment rebates are available.

Use an integrated system approach

The conventional approach to upgrading a heating and cooling system is to address each component of the system individually. However, addressing the interaction between the components using an integrated system approach ultimately results in a more energy-efﬁ cient system. In addition, compared with assessing components individually, assessing upgrade opportunities for whole systems consumes less time, and therefore less money, in the long term.

Heating and cooling system components, particularly in central systems, interact with each other extensively. For example, chillers operate more efﬁ ciently if they receive cooler condenser water. However, the cooling tower fans consume more energy to provide cooler condenser water.

Optimizing the energy use of the cooling tower/chiller system is one example of using an integrated system approach that can improve your energy performance and save money.

Heating and cooling system capacity and energy use

Cooling may use as much as a third of the electricity consumed in a typical building. Heating systems use natural gas or oil as the primary fuel, but also may use electric-ity. Heating and cooling systems condition the air within a building so that occupants are comfortable. These systems consist mainly of chillers, boilers, cooling towers and pumps.

IS NEW EQUIPMENT A GOOD IDEA?

If you’re wondering whether you’re better off maintaining your existing system or upgrading to new, consider this:

• The average efﬁ ciency of all units now being bought has risen by 14 percent compared with the 1992 U.S. standard

• The most efﬁ cient units now are 52 percent more efﬁ cient than the standard • Air conditioning is the second largest consumer of electricity in commercial buildings

(after lighting)

• Air conditioning is the largest contributor to peak electricity demand during hot weather

• Conclusion: If your cooling system is more than 15 years old, it uses up to 20 percent more electricity than new models and is likely to be increasingly unreliable and hard to maintain. It’s time to consider an upgrade to a more-efﬁ cient system. Keep in mind that a scheduled replacement can generally be negotiated at a lower cost and with less inconvenience than an emergency replacement of a failed unit

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Cooling systems generally have higher space conditioning capacities than heating systems, because a large portion of the building’s heating requirements is supplied by waste heat from its people, lighting and offi ce equipment. The proper design and operation of these systems can translate into signifi cant savings. If you have followed energy-saving steps in other areas of your building, your cooling load may now be low enough to justify retrofi tting or rightsizing your cooling system.

Save energy and money with

cooling upgrades and improvements

Cooling system rebates available

Cooling Efﬁ ciency, by ConservationWise from Xcel EnergySM_{offers rebates}

for electricity business customers who install qualifying energy-saving cooling equipment, including:

• Chillers

• Condensing units

• Hotel-room occupancy sensors • Oversized cooling towers

• Packaged terminal air conditioners (PTAC) • Rooftop units and/or economizers

• Split systems

• Variable air volume (VAV) boxes • Water-source heat pumps

Call your account manager or our Business Solutions Center at 1-800-481-4700 for more information on how you can earn Cooling Efﬁ ciency rebates.

Unitary systems: rooftop units, split systems and others

Unitary systems are factory-assembled cooling — or combined heating and cooling — systems. Cabinet- or skid-mounted for easy installation, typical units generally consist of an evaporator, blower, compressor, condenser and, if a combined system, a heating section.

The size of the units ranges from approximately 1.5 to 130 tons.

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Unitary systems are generally used in one-, two- or three-story buildings that have small cooling loads, such as retail spaces, small ofﬁ ce buildings and classrooms.

systems and water-source heat pump systems. Compared with central chiller plants, unitary systems do not last as long (only 12 to 15 years) and are less efﬁ cient. Generally speaking, it is not feasible to convert a building from these packaged units to central chilling. However, it is not always necessary to replace in kind – sometimes switching to a heat pump or other efﬁ cient system is feasible.

Whether your building uses unitary systems for cooling, heating or both, you can ben-efi t from an integrated system approach. Depending on the other effi ciency upgrades you have implemented in tune-ups through fan systems, cooling load requirements might have been reduced between 10 percent and 40 percent. It’s common for existing unitary systems to be oversized. Likewise, unitary systems that are in poor condition suffer downtime and signifi cantly increased operating and maintenance costs. A new and more reliable unitary system may be more cost effective. If your unitary systems are 10 years old or older, you can realize energy savings by replacing unitary systems with rightsized, energy-effi cient models.

Packaged or rooftop units

Packaged or rooftop units are packaged HVAC units that are usually mounted on the roof, freeing up valuable indoor ﬂ oor space. They also can be installed on a concrete pad at ground level. Because they are self-contained, manufactured units, installation costs are low.

Single-package units consist of a blower section, ﬁ lter bank, evaporator coil, at least one compressor (larger units typically have multiple compressors to improve load matching) and an air-cooled condenser section.

CASH DISCOUNTS ON SUMMER ELECTRIC BILLS

Last year, a Stillwater insurance agency saved 28 percent on summer energy bills without investing a penny. You, too, can ensure energy savings with Saver’s Switch.

Saver’s Switch pays you a monthly discount of $5 per ton of enrolled air conditioning on your business’s electricity bills from June through September. Most customers have about 5 tons of air conditioning included, which saves them $100 each summer – and customers with larger systems can save much, much more.

On the hottest summer days when our customers use the most electricity, we use the pager-activated Saver’s Switch to adjust your air conditioner so it cycles off and on at 15- to 20-min-ute intervals. While it saves electricity, most customers never notice a difference – until they see their discounted bills. There’s no enrollment fee or hidden charge.

Contact your Xcel Energy account manager or our Business Solutions Center at 1-800-481-4700 to see if Saver’s Switch might be right for you.

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Units also may come equipped with a heating section. Heating is accomplished using either natural gas or electricity; however, natural gas is generally less expensive, depending on the region.

As packaged units age and deteriorate, their efﬁ ciency often decreases while the need for maintenance increases. Upgrading your packaged units to high efﬁ ciency models will result in substantial long-term energy savings.

In the last 10 to 15 years, manufacturers have made signiﬁ cant improvements to the efﬁ ciency of packaged units in the following ways:

• The efﬁ ciency of heat transfer at both the evaporator and condenser coils has been improved

• High efﬁ ciency motors are now standard

• Blower and compressor designs have improved in high-efﬁ ciency packaged units • Scroll compressors are now commonplace on medium-size (20- to 60-ton)

rooftop units

• Energy effi ciencies of newer units have a SEER in the range of 9.50 to 13.0. It is not uncommon to fi nd older units operating at effi ciencies as low as 6.0, and most operate at less than 9.0

All newer packaged rooftop units are equipped with factory-installed microprocessor controls. These controls make maintaining equipment easier and improve the energy efﬁ ciency of both the unit and the overall HVAC system. Control features include temperature setback and on/off scheduling.

Large systems have variable air volume capability. Also, most units have an optional communication interface for connection to an energy management system (EMS). Split-system units

Split-system packaged units have an outdoor pad or rooftop-mounted air-cooled condenser. Refrigerant piping connects the compressor section to an indoor air-handling unit and evaporator coil.

Rightsizing

Rightsizing your unitary systems to maximize the benefi ts of cooling and heating load reduc-tions can result in signifi cant energy savings. When determining the rightsizing potential of your unitary system, be sure to measure your cooling and heating loads fi rst using the survey. Please note that the Annual Cost Savings chart mentioned in No. 4 of the Unitary Systems Survey is on page 12 of this guidebook.

How much can a high- efﬁ ciency rooftop unit save?

For a typical 100,000-sq. ft. offi ce building that has 10 standard 25-ton packaged units with a EER rating of 9, electricity costs would be about $53,300 for cooling at $0.08 per kWh. Installing new energy- effi cient units with a cooling energy effi ciency rating of 13 would result in cooling mode electricity costs of about $36,900 annually—a savings of $16,400 per year. The annual savings equals a reduction in cooling costs of more than 30 percent. Note: The cooling units are assumed to operate for 2,000 hours per year – your equipment, effi ciency, usage and electricity costs may vary from this example.

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Residential units in business buildings Typically, commercial buildings use unitary systems with cooling capacities greater than 5 tons. In some cases, however, due to space requirements, physical limitations or small additions, residential-sized unitary systems are used.

In these cases, be sure to look for the ENERGY STAR®_{label. It’s found on} various high-efﬁ ciency heating, cool-ing and control products, and can help you differentiate between these and standard- efﬁ ciency products.

SURVEY

Unitary Systems Survey

Collect the following information for each type of unit installed in your building: System type (choose one)

❑ Packaged rooftop unit ❑ Split system

❑ Vertical packaged unit ❑ Heat pump

Manufacturer ____________________________________________________________ Heating fuel (gas, oil, elec.) ________________________________________________ Unit age ________________________________________________________________ Cooling efﬁ ciency (%) ____________________________________________________ Heating efﬁ ciency (%) ____________________________________________________ Size or capacity (cooling) _________________________________________ (in tons) Size or capacity (heating) ______________________________________(in MBtu/hr) Calculate the maximum cooling and heating loads for your building using the following steps:

1. What are the maximum heating and cooling loads for the building (in MBtu/hr)? • These loads will be compared with the cooling and heating capacities

recorded above.

• To determine maximum heating or cooling load for systems that respond to thermostats by cycling on and off, a simple runtime meter will show how much of the time the unit cycles on.

• Supply-temperature data logged every few minutes by an EMS or other data logger can also be analyzed to determine how much of the time the unit is cycled on. The percentage of heating capacity needed is the time the unit operates divided by the total time during a high heating load period. 2. Time cycled on ÷ total time = percentage of capacity needed

• A data logger can be used to determine how much of the time the unit is cycled on.

• By knowing what your cooling and heating loads are, you will be better able to rightsize your new unitary system to meet maximum loads. 3. To estimate your energy savings from rightsizing, ﬁ rst measure your cooling and

heating loads. Then, using the seasonal energy efﬁ ciency ratio (SEER) for your old and new systems, compare their respective energy consumption.

4. Contact your equipment manufacturer or an engineering consultant for further assistance, or use the Annual Cost Savings chart to get an at-a-glance feel for your

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Annual cost savings chart

This chart is available on xcelenergy.com on the

cool-ing efﬁ ciency Web page, or call the Business Solutions Center 1-800-481-4700 to request a copy.

Use this Annual Cost Savings chart to calculate energy savings for energy-effi cient equipment that qualifi es for the Cooling Effi ciency program brought to you by ConservationWise from Xcel Energy.SM_{Effi ciencies below the red line* are eligible for rebates.}

Notes:

Operating Hours/Yr (866 Full Load Hours) One shift operation, 10hrs/day, 5 days/wk, May 15 - Oct. 15 Base Operating Eff 6.00 Efﬁ ciency (SEER or EER - BTU/WATT)

1. To determine annual cost savings, subtract operating cost differences for unit sizes and efﬁ ciencies (e.g. 5 Ton Unit Existing SEER = 8.00, Proposed SEER = 12.00, Annual Savings = $410.59 - $205.29 = $205.30/yr)

2. Savings Table represents annual cost savings for one shift operation of typical ofﬁ ce building (i.e. 10 hrs/day, 5 days/wk) 3. For two shift operation (i.e. 17 hrs/day, 5 days/wk), multiply savings by 1.6 (e.g. $205.30 x 1.6 = $328.48/yr)

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Contact your Xcel Energy account manager or our Business Solutions Center at 1-800-481-4700. Sign up for conservation-related e-mails about rebate programs, bonus offers and special events at xcelenergy.com/subscribe 4. For three shift operation (i.e. 24 hrs/day, 5 days/wk), multiply by 2.0

5. For 24 hr/day, 7 days/wk, multiply by 2.8 6. DISCLAIMER

This annual cost savings chart is for illustrative purposes only and is based upon Xcel Energy calculations to ESTIMATE energy and cost savings. You or your contractor may wish to use the same or different methodology to estimate savings. Moreover, Xcel Energy only use calculations to estimate savings, which may vary from actual results depending on a number of factors. Xcel Energy does not guarantee the amount of energy or cost savings, nor does Xcel Energy endorse or guarantee the work of contractors and/or vendors you select to perform energy services.

7. Please reference the Cooling Efﬁ ciency rebate application #0221 for accurate qualiﬁ cation guidelines.

To apply for a speciﬁ c rebate or to receive more information regarding the Cooling Efﬁ ciency program, talk to your Xcel Energy sales represen-tative or call our Business Solutions Center at 1-800-481-4700. Also check the Web site at xcelenergy.com for more information about how to save money and energy.

Central cooling systems – chillers

There are four types of mechanical compression chillers — centrifugal, screw, scroll and reciprocating; different applications call for different chiller types. Generally, older chillers have efﬁ ciencies ranging from 0.8 to 1.0 kW/ton; they often consume approximately twice the energy of newer, more efﬁ cient chillers.

Today, centrifugal chillers have efﬁ ciencies as low as 0.45 kW/ton. The table below shows the efﬁ ciency ranges for newer chiller technologies.

Common Chiller Types and Efﬁ ciencies

Chiller Type Size Range (tons) Full-load Efﬁ ciency (kW/ton) Centrifugal 100 - 1,500+ 0.45 - 0.68 Screw 40 - 1,100 water-cooled 0.56 - 0.70 air-cooled 1.1 - 1.3 Reciprocating 1 - 400 water-cooled 0.8 - 1.0 air-cooled 0.97 - 1.6

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Chiller retroﬁ t

If the existing chiller is less than 10 years old, retroﬁ tting the chiller to operate on non-CFC refrigerants at the newly reduced loads will probably be your most proﬁ table option. This postpones investing in a new chiller.

When you are replacing refrigerant, use HCFC-123 in place of R-11 and HFC-134a in place of R-12. Retrofi tting may involve replacing orifi ce plates, impellers, gaskets or even the com-pressor. The specifi cs of the retrofi t depend on the type of chiller and its manufacturer. Many manufacturers offer retrofi t kits for their chillers. Contact the manufacturer of your chiller to determine its requirements.

Due to their inherent properties, non-CFC refrigerants are not as efﬁ cient and thus will affect chiller efﬁ ciency by reducing its cooling tonnage at current or even increased levels of energy consumption. However, the reduced cooling loads obtained through performing a comprehen-sive upgrade will offset this loss.

Eliminating CFCs: headache or opportunity?

CFC refrigerant production was phased out by law in 1996. As existing stock of CFCs dwindle and become more expensive, conver-sion to or replacement with non-CFC chillers is becoming more cost effective. Existing, relatively new chill-ers may be cost effective to retroﬁ t for non-CFC operation.

Replacing an older chiller with a new, non-CFC chiller is an excellent opportunity to

in-vest in a high efﬁ ciency unit. First cost for the installation will be reduced by installing a smaller chiller made possible by the implementation of all upgrade opportunities.

CFCs Are on The Way Out

Eighty percent of todays existing chillers are centrifugal chillers that use R-11 refrig-erant. The newer, non-CFC alternative to R-11 is HCFC-123. Some centrifugal chillers use R-12; its non-CFC alternative is HFC-134a. Unitary air conditioning units typically use R-22, which will be phased out in the future.

Phase-Out Date Refrigerants Action

Source: ASHRAE Fundamentals Handbook, 2001.

1996 2010 2020 2030 2030 R-11, R-12, R-500, HCFC-152A, CFC-114 HCFC-22 HCFC-123 HCFC-22 HCFC-123

Production of these refrigerants has stopped. Equipment using these refrigerants is no longer manufactured.

Manufacture of equipment using this refrigerant has stopped. Manufacture of equipment using this refrigerant has stopped. Production of this refrigerant has stopped.

Production of this refrigerant has stopped.

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Chiller rightsizing

Depending on the efﬁ ciency improvements you’ve made in other parts of your build-ing, loads on your cooling system might have been reduced by at least 10 percent, and perhaps by as much as 40 percent.

Even if you haven’t implemented upgrades, design loads and actual building demand rarely match. Chillers are frequently oversized, and those in poor condition suffer downtime and signiﬁ cantly increased operating and maintenance costs.

A new effi cient and reliable chiller may be more cost effective. Thus, you may want to consider rightsizing your existing chiller with a new, smaller, energy-effi cient one that matches the newly reduced loads and uses compliant non-CFC refrigerants. This option is most profi table when your existing chiller is more than 10 years old.

When you decide to replace an existing chiller with an energy-efﬁ cient unit, be sure to evaluate the initial operating and maintenance costs, size and weight of the new unit. Keep in mind that the energy consumption of a new high-efﬁ ciency chiller could range from 15 percent to more than 50 percent less than that of the existing chiller.

While the new chiller must be sized for peak loads, be sure that it operates effi ciently at part-load conditions, because the chiller operates at part load most of the time. An energy services professional or consulting engineer can develop the new peak load profi le. To analyze the profi tability of chiller upgrades, you will need to identify the relationship between outdoor air temperature and the cooling load that the chillers must meet. Consult the chiller manufacturer’s specifi cations to prepare a load profi le for your building compiled using a heating and cooling survey (see page 16 for a survey worksheet).

To evaluate the chiller project, gather data about existing chillers, operating schedules, utility rate schedules, cooling tower parameters and water reset temperatures for the condenser and evaporator. Use this Chiller System Survey as a tool to analyze your system.

Many chiller manufacturers provide electronic copies of their equipment speciﬁ cations catalogs on CD-ROM. This information can be used to identify the appropriate chiller for your facility, once you have analyzed the building’s peak load proﬁ le.

BE SURE YOU’RE ON THE BEST RATE FOR YOUR BUSINESS

We offer special reduced rates for customers who can cut their energy use during peak- demand periods.

Our money-saving Electric Rate Savings options aren’t right for all customers, but offer valu-able cost-saving options if you have backup power availvalu-able or are willing to make changes that can lower your demand by at least 50 kW when needed.

Learn more about these discounts from your Xcel Energy account manager or our Business Solutions Center at 1-800-481-4700.

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SURVEY

Chiller Systems Survey

Chiller type (choose one)

❑ Air-cooled centrifugal ❑ Water-cooled centrifugal

❑ Reciprocating ❑ Helical rotary/screw

❑ Steam absorption ❑ Hot-water absorption

❑ Direct-ﬁ red absorption ❑ Engine-driven

Manufacturer ____________________________________________________________ Type of refrigerant _______________________________________________________ Age ____________________________________________________________________ Efﬁ ciency (kW/ton) _______________________________________________________ Size or capacity (in tons) _____________________________ (12,000 Btu/hr = 1 ton) Calculate the maximum cooling load for your building using the following procedure: 1. What is the maximum cooling load for the building (in tons)?

• This load will be compared with the chiller capacity recorded above. To determine maximum cooling load, take the following measurements in the afternoon on a typi-cal hot summer day to capture peak load effects on your system. Note: An energy management system may also log these measurements.

2. Temperature of the chilled-water supply (CHWS). A temperature gauge should be found on the pipe at the chiller’s supply outlet.

3. Temperature of the chilled-water return (CHWR). A temperature gauge should be found on the pipe at the chiller’s return inlet.

4. Flow rate (GPM) of the chilled-water supply. A ﬂ ow-rate gauge should be found on the sup-ply pipe. If a gauge is not available, the design ﬂ ow rate from as-built drawings may be used.

Chilled-water system

Measurements

Temperature of CHWS______________________ Temperature of CHWR ______________________ Flow rate (GPM) of CHWS __________________

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Contact your Xcel Energy account manager or our Business Solutions Center at 1-800-481-4700. Sign up for conservation-related e-mails about rebate programs, bonus offers and special events at xcelenergy.com/subscribe MAJOR COMPONENTS OF A TYPICAL CHILLER SYSTEM

Calculations

Now, using the measurements, do the following calculations: 1. CHWR – CHWS = T:

2. T x 500 x (GPM ÷ 12,000) = load (in tons): 3. Load x 1.1 = maximum cooling load

4. How much of your existing chiller capacity does your building currently need? • To answer this, do the following calculation:

Maximum cooling load ÷ chiller capacity = 5. Percentage of chiller capacity needed =

• If the required capacity of the chiller is 30 percent less than the installed capacity of your existing chiller, you should seriously consider replacing the chiller. The efﬁ ciency of the chiller decreases sharply below 70 percent loading. Also, remember that the chiller is operating most of the time at part load conditions, which increases your rightsizing potential even further.

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Upgrading chiller components

You can upgrade numerous components of a chiller system to improve system efﬁ ciency and increase cooling cost savings.

Cooling tower improvements

Central cooling systems generate heat that must be rejected outside the building, and a cooling tower is commonly used for this purpose. All cooling towers function as large heat exchangers, transferring heat from the condenser side of the chiller to the outside air by spraying the hot water through a ﬂ ow of outside air. This ﬂ ow of outside air is created with centrifugal or axial fans mounted at the lower end of the tower in the forced-draft tower.

A more common type of tower, the induced-draft tower, uses a propeller fan at the top of the tower to pull air up through the tower. The induced-draft tower offers better aerodynamics and is generally more effi cient than a forced-draft tower. The forced-draft tower is generally quieter and requires less space than an induced-draft tower, but operates at a lower effi ciency. Both forced-draft and induced-draft cooling towers employ a surface contact medium or fi ll to in-crease contact surface and improve the transfer of heat between hot water from the chiller and the outside air.

Scaling, corrosion and biological growth all impede tower efﬁ ciency and increase maintenance costs from the resultant condenser fouling and loss of heat transfer. Chemical treatment is gen-erally used to mitigate these problems. However, new, nonchemical water treatment technolo-gies, such as ozone generators, magnetic systems and ultraviolet irradiation, are available.

• Ozone is a powerful oxidant and biocide that can replace chemicals completely in some cases

• Magnetic systems are designed to cause scale-forming minerals to precipitate in a low-temperature area away from heat exchanger surfaces, thus producing non-ad-herent particles. The precipitated particles can then be removed by blowdown, me-chanical means or physical ﬂ ushing. The effectiveness of a magnetic system can be diminished by a low ratio of dissolved calcium to silica, by the presence of excessive iron in the water, or if it is installed close to high-voltage power lines

Two-speed fan motors in combination with fan cycling provide an improvement in control and efﬁ ciency over fan cycling alone. Variable speed drives (VSDs) provide the most efﬁ cient method of control.

Cooling tower fans offer similar energy-saving opportunities. Fan power is proportional to the cube of the airﬂ ow rate; thus, a reduction of 20 percent in fan airﬂ ow (and speed) will correspond to a reduction of 49 percent in fan power.

Free cooling (water-side economizer)

Under the right conditions, free cooling or a water-side economizer system can generate signiﬁ cant energy savings.

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Several methods of free cooling are available

• The most common method is a type of indirect free cooling that uses a separate heat exchanger, typically of the plate-and-frame type. It allows for a total bypass of the chiller, transferring heat directly from the chilled water circuit to the condenser water loop.

• A less common method is direct free cooling, in which the condenser and chilled water circuits are linked directly without the use of a separate heat exchanger. A disadvantage of using direct free cooling is that bacteria pres-ent in the cooling tower water system may contaminate your chilled water circuit. You can, however, install ﬁ ltration systems or strainers to minimize this risk.

CUSTOM REBATES AVAILABLE FOR A VARIETY OF COOLING PROJECTS

Custom Efﬁ ciency, by ConservationWise from Xcel Energy_{ConservationWise from Xcel Energy}_{ConservationWise from Xcel Energy}SMSM_{, offers}

rebates for equipment or process improvements that don’t qualify for our standard rebates, but increase energy efﬁ ciency by:

• Decreasing the amount of energy used, or

• Increasing the number of units produced per unit of energy

All Custom Efﬁ ciency rebates require preapproval prior to purchase and installation. While any project has the potential to qualify, these projects have a history of earning Custom Efﬁ ciency cooling rebates:

Cooling and heating - equipment

• Air conditioning economizers • Boilers, heaters and makeup air units • Chillers

• Economizers • Free cooling • Furnaces

• HVAC heating and cooling control schemes (weekday, weekend, evening settings) • Insulation (ceiling, wall, water heaters,

hot-water distribution pipes) • New energy-efﬁ cient HVAC equipment • PTAC units

• Rooftop and condenser units

• Window ﬁ lms, blinds, awnings and solar screen shades

Controls - applications

• CO2 based ventilation • Compressed air systems • Daylighting

• Energy management systems (EMS) • Energy recovery

• HVAC control (PTAC controls) • Morning preheat/cool down • Night setback, day setup • Start/stop

• Temperature resets

Cooling and heating - concepts

• Eliminate simultaneous heating and cooling • Improve chilled water ﬂ ow

• Match operation and equipment with current occupancy

• Minimize equipment cycling (boilers, cooling fans, etc.)

• Minimize supply and return fan amps • Optimize enthalpy control of

economizer function

• Optimize mixed air control based on occupancy • Optimize operation during periods of

low occupancy

• Optimize supply air temperature and relative humidity

• Reduce CFM during periods of low occupancy • Restore or improve economizer function

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Facilities that require year-round cooling from high sensible heat gains would most likely beneﬁ t from direct free cooling. A large computer room or data center cooled with a central chilled-water system would be a promising application. When ambient outdoor conditions are ideal (that is, when the wet-bulb temperature is low enough), the chiller can be shut off and the cooling load may be served exclusively by the cooling tower without the energy-intensive mechanical refrigeration. The resulting reduction in energy consumption can be dramatic.

Pumping system upgrades

In buildings that use pumps to transport chilled water or condenser water, an integrated system approach can reduce pumping system energy by 50 percent or more. You can make your pumping systems more energy efﬁ cient by:

• Replacing oversized impellers, pumps and motors with rightsized pumps and smaller, energy-efﬁ cient motors

• Installing VSDs on pump motors

• Converting single-loop conﬁ gurations to primary-secondary loop conﬁ gurations Rightsizing pumps

Rightsizing pumps to accommodate lower maximum loads can result in energy savings of up to 70 percent. The most cost-effective method is often trimming or replacing an oversized impeller in an existing centrifugal pump.

When pump rightsizing, maximum design capacity of the new impeller or pump must be greater than the measured maximum load for the system. Be certain that the new motor is an energy-efﬁ cient model, sized to meet the maximum load, and recognize that pump motors, like fan motors, come in incremental sizes (5 hp, 7.5 hp, 10 hp, etc.).

Calculate your energy savings from rightsizing by comparing rated energy curves at various loads for old and new pump and motor sizes. Contact the pump manufacturer or an engineer-ing consultant for further assistance.

Variable-speed drives (VSDs)

Installing VSDs will ensure that your pumps are performing at maximum efﬁ ciency at part-load conditions. Similar to the fan systems, the power required to operate a pump motor is proportional to the cube of the speed. For example, in a pump system with a VSD, a load reduction that results in a 10-percent reduction in motor speed reduces energy consumption by 27 percent [1 – (0.9)3 = 0.27].

Estimating savings from installing VSDs on pumps

To estimate the annual energy savings you can gain from installing VSDs on pumps, estimate run times for all part-load conditions, based either on monitoring or load calculations.

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When installing VSDs, be sure to:

• Complete harmonic, power factor, and torsional analyses before installation • Conduct a coast-down test to compare mechanical resonance with

speed response

• Ensure that maximum and minimum ﬂ ow rates through the chiller can be met with chiller pump upgrades

Single-loop conversions

The rated minimum fl ow for chilled water through the chiller is typically 70 percent of maximum, which also applies to VSD fl ow reductions. However, a primary-secondary loop confi guration, also known as a production-distribution confi guration, can allow for greater energy savings without compromising your chiller performance.

With the primary-secondary loop confi guration, chillers are equipped with smaller chilled-water pumps, or primary pumps. These are constant-fl ow pumps that operate with a lower pressure drop than in a single-loop confi guration.

Variable-ﬂ ow secondary pumps then distribute the chilled water through your build-ing’s end-use air-handling devices and have the capability of reducing their speed at part-load conditions.

When converting from a single-loop conﬁ guration to a primary-secondary conﬁ gura-tion, be sure to:

• Pipe the lower velocity chiller bypass water on the production side to ﬂ ow into the higher velocity chilled water return on the distribution side and not vice versa

• Replace three-way valves at air-handling unit coils with two-way valves • Maintain maximum and minimum ﬂ ow rates through the chiller EXAMPLE OF VSD SAVINGS

• Install a 30-hp VSD on a chilled-water pump

• The existing ﬂ ow rate is 1,040 gallons per minute (GPM), existing operating hours are 3,300 per year, and the pump’s energy consumption is 66,900 kWh per year

• The initial cost of the VSD is $7,175. The VSD reduces average ﬂ ow to 700 GPM • Estimated new annual energy consumption: (66,900)(700 ÷ 1,040)3 = 20,400 kWh per year • Estimated annual energy savings: (66,900 – 20,400)($0.08/kWh) = $3,720 per year • Simple payback = $7,175 ÷ $3,720 = 1.9 years

Note: Your electric rate and energy usage may vary from those presented in this example.

VSDs may qualify for a Motor Efﬁ ciency rebate, by ConservationWise

from Xcel Energy.SM_{Contact your} Xcel Energy account manager or our Business Solutions Center at 1-800-481-4700 for details.

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Be sure to locate the thermostat in a location where the temperature is representative of the entire area served by the system — not next to the air-conditioning diffuser or a coffee pot or in direct sunlight.

Save energy and money with your

current HVAC system

Thermostat adjustments and setback thermostats

The most straightforward method for saving on your HVAC bill is simply to operate the systems less, both by turning the systems off (or back) when the building is not occupied and by choosing more efﬁ cient temperature set points so that the systems run less often.

Set back your thermostat to reduce high energy bills

Signiﬁ cant savings are available by setting back your thermostat when the building is unoccupied. The term “setting back” is used to indicate both changing the temperature setting to a higher temperature during summer and making sure that the fan switch on the thermostat is set to “auto” rather than “on.” A fan left in the “on” mode runs nonstop 24 hours per day; in “auto” mode, the fan cycles on only when heating or cooling is being supplied. In some instances the fan savings can be signiﬁ cant even when only minimal temperature setback changes are made. Raise your building temperature slightly during operating hours

Substantial savings also are available by adjusting your temperature setpoints — lower in the winter and higher in the summer. Change your thermostat settings gradually, no more than a degree or so per week, to see how low a setting you need to maintain a comfortable facility. Make these changes without advertising the fact that you are doing so to avoid having employees notice changes before they can actually feel them.

This method also can help identify problem areas in your system. Check out the areas where you ﬁ rst receive complaints about comfort to determine whether the problem is one of inadequate air supply, excessive drafts or intense sunlight.

Programmable thermostats make setbacks a sure thing

Although night-setback and temperature-setpoint changes are simple enough to do manually, an automatic control is much more efﬁ cient and reliable.

Electronic, programmable thermostats that allow you to program in desired setpoint and setback times for each day of the week are available for $30 to $200. Most models include manual override features, so an executive who needs to come in on a Sunday afternoon A week contains 168 hours.

If your business operates during only 40, or even 80, of those hours, you occupy your facility during only a fraction of the week and have large potential savings during unoccupied hours. .

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Many businesses ﬁ nd it worthwhile to install a locking enclosure around their thermostats to avoid unauthorized tampering with the setpoints.

Have a heat pump? Set back its thermostat for savings

If you have a heat pump, be sure you get a heat-pump-programmable thermostat with a “smart recovery” feature, which will bring your system on early enough to ensure comfort. Heat-pump thermostats cost about twice as much as other thermostats because they have to control multiple types of heating, plus cooling.

Whole-building energy optimization and management systems

Programmable thermostats are effective and work quite well, especially with indi-vidual-unit air conditioners and heaters. But if your facility uses larger, central systems such as boilers and chillers, you may wish to use an energy management system (EMS) instead. The EMS market also is expanding into smaller and smaller facilities using shared EMS systems and new Internet-based technology.

In addition to the setpoint and night-setback features, which can be handled by a programmable thermostat, an EMS can provide savings in many other ways. Depending on the type of system you have, an EMS might be used to provide some of the following money-saving automatic control functions:

• Adjust supply-air temperatures based on indoor and outdoor temperature and humidity to let the heating and cooling systems operate most efﬁ ciently • Adjust chilled-water and hot-water temperatures based on indoor and

outdoor temperature and humidity to let the cooling and heating systems operate most efﬁ ciently

• Implement holiday period automatic setpoint adjustments

• Monitor space temperatures to minimize overheating or overcooling of spaces on a zone-by-zone basis

• Manage your electrical loads, prevent peak loads and optimize your electrical rate with your electric utility

An EMS can be used to control other functions in your building as well, such as lighting. It can be monitored and controlled from a console in a remote location, such as your home or your maintenance manager’s home.

EMS suppliers typically estimate that their EMS can cut the heating and cooling bills of a business with a central chiller and heating system by 10 percent to 50 percent (many estimates are clustered in the 20-percent range).

Energy Management Systems, by Conser-vationWise from Xcel

EnergySM_{, offers rebates to customers}

who install a qualifying stand-alone or shared EMS in their facility.

Contact your Xcel Energy account manager, or our Business Solutions Center at 1-800-481-4700 to discuss your options before you purchase or install an EMS.

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HVAC tune-ups – an annual necessity

We recommend scheduled maintenance on your cooling systems annually by a licensed HVAC contractor. Regular maintenance is an often-overlooked key to saving on your HVAC costs and improving the performance of your system. Annual maintenance can save up to 50 percent or more on summer cooling costs.

Although some maintenance jobs may require calling in an outside technician, many can be accomplished inexpensively using in-house staff. Because it also extends the life of your HVAC equipment, regular maintenance provides signiﬁ cant cost savings for minimal investment. If you have an annual maintenance contract, be sure your check includes all of these steps.

Recommissioning saves up to 15 percent without significant

capital investment

Our Recommissioning program, by ConservationWise from Xcel EnergySM_{, optimizes your}

buildings existing systems to help them run more efﬁ ciently. Most improvements identiﬁ ed are low- to no-cost with payback periods of less than one year.

Consider this: If you spend about $20,000 on annual energy bills, Recommissioning could help you save up to $3,000 each year – and many customers save much more.

Commissioning is a quality assurance process to verify that the building’s systems meet the building’s needs at start up. Our Recommissioning program looks at buildings that were com-missioned but no longer work as well as you wish, or buildings that never were comcom-missioned. In addition to energy savings, Recommissioning can help you extend equipment life, improve indoor air quality and reduce operating and maintenance costs. Typical Recommissioning im-provements include:

• Optimizing supply-air temperatures • Optimizing condenser water temperatures • Eliminating simultaneous heating and cooling • Optimizing outside air quantities

• Improving economizer control • Optimizing unoccupied setback

We offer funding for Recommissioning studies, and rebates when you make improvements recommended in your study.

Contact your Xcel Energy account manager or our Business Solutions Center at 1-800-481-4700 for details, including a list of Recommissioning providers who have successfully completed a project in the past.

Annual cooling system maintenance and system checks are just as important as changing the oil in your vehicle every 3,000 miles.

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What should your cooling tune-up include?

❏ Check the system’s connections

❏ Inspect and clean coils, straighten ﬁ ns, and replace ﬁ lters

❏ Inspect and oil fan motors

❏ Inspect and repair ductwork leaks and insulation voids in unconditioned spaces

❏ Check for proper ventilation and economizer operation. Have a licensed technician check, adjust, clean and lubricate your economizer each year — one stuck in the open position can add up to 50 percent to your annual HVAC costs. If necessary, adjust the outdoor intake setting on your econo-mizer — code generally requires 20 cubic feet per minute (cfm) of outdoor air per person, but many units bring in more air than is necessary

❏ Check for proper airﬂ ow at unit and each zone

❏ Check for proper control settings and safety shut-down functions

❏ Clean condenser coils — at the beginning and end of the cooling season thoroughly wash the coils. Check them quarterly for man-made or natural debris and wash as necessary

❏ Trim plants/shrubs away from cooling equipment to ensure adequate air ﬂ ow

❏ Change ﬁ lters as needed (minimum quarterly; recommended monthly or more if you’re located next to a highway, construction site or other location where air is dirtier than usual)

❏ Check refrigerant levels (usually done by a licensed technician)

❏ Adjust fan settings — set the fan to “auto” during unoccupied hours rather than leaving it “on” around the clock

❏ Check air temperature — using a thermometer, check the temperature of the return air going to your air conditioner, and then check the tempera-ture of the air coming out of the register nearest your air conditioning unit. If the temperature difference is less than 14 F or more than 22 F, have a licensed technician inspect your cooling system

❏ Check cabinet panels — each quarter, make sure rooftop air conditioning panels are fully attached, with all screws in place and gaskets intact. Chilled air leaking out of the panels can cost up to $100 per rooftop unit per year in wasted energy

❏ Check airfl ow — hold your hand up to registers to ensure you can feel the airfl ow. If there is little airfl ow or you see dirt and dust in the register, have a technician inspect your unit and ductwork

Contact your Xcel Energy account manager or our Business Solutions Center at 1-800-481-4700. Sign up for conservation-related e-mails about rebate programs, bonus offers and special events at xcelenergy.com/subscribe

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References

Xcel Energy thanks ENERGY STAR®_{for allowing us to use its information to provide you a}

comprehensive guidebook. For a free copy of the resource booklet Putting Energy Into Proﬁ tsPutting Energy Into Proﬁ ts, contact ENERGY STAR at 1-800-STAR-YES or visit energystar.gov. Or view their Heating and Cooling Upgrades information available at energystar.gov/ia/business/Heating.pdf

We also thank the HVAC&R Center at the University of Wisconsin Madison, E Source and ASHRAE for information used to compile the guidebook.

Resources

Conservation rebates from Xcel Energy, visit xcelenergy.com/rebates

Additional resources

American Society of Heating, Refrigerating and Air-Conditioning Engineers (ASHRAE), visit ashrae.org for national information, or mnashrae.org for Minnesota chapter information Consortium for Energy Efﬁ ciency, Inc, visit cee1.org

ENERGY STAR buildings and equipment, visit energystar.gov

Energy-related tax incentives, visit energytaxincentives.org

Facility management information, visit facilities.net

U.S. Department of Energy – Ofﬁ ce of Energy Efﬁ ciency and Renewable Energy, visit eere.energy.gov/buildings/

U.S. Department of Energy, visit energy.gov

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Notes

Contact your Xcel Energy account manager or our Business Solutions Center at 1-800-481-4700. Sign up for conservation-related e-mails about rebate programs, bonus offers and special events at xcelenergy.com/subscribe

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Xcel Energy is a trademark of Xcel Energy Inc. Northern States Power Company-Minnesota Printed with soy-based inks on recycled paper. CSS 1764 05/2006 06-05-207

Summer cooling savings guidebook