CHAPTER 9. TRIAL STANDARD LEVELS
 

TABLE OF CONTENTS
 

9.1 INTRODUCTION .............................................................................................................. 9­1
 

9.2 TRIAL STANDARD LEVELS .......................................................................................... 9­1
 

9.3 ENERGY­EFFICIENCY EQUATIONS............................................................................ 9­4
 

9.3.1 Existing Federal Energy­Efficiency Equations for PTACs and PTHPs and the

Energy­Efficiency Equations in ASHRAE Standard 90.1­1999 in the Cooling Mode ...... 9­5

9.3.2 Revised Energy­Efficiency Equations for Standard Size PTACs and PTHPs in the

Cooling Mode ..................................................................................................................... 9­6

9.3.3 Rationale for Revised Slope of TSL A for Standard Size PTACs and PTHPs in the

Cooling Mode ..................................................................................................................... 9­8

9.3.4 Revised Energy­Efficiency Equations for Non­Standard Size PTACs and PTHPs

in the Cooling Mode ......................................................................................................... 9­10

9.3.5 Existing Federal Energy­Efficiency Equations for PTACs and PTHPs and the

Energy­Efficiency Equations in ASHRAE Standard 90.1­1999 in the Heating Mode .... 9­14

9.3.6 Revised Energy­Efficiency Equations for Standard Size and Non­Standard Size

PTACs and PTHPs in the Heating Mode.......................................................................... 9­16

LIST OF TABLES

Table 9.2.1 Standard Size Equipment Baseline Efficiency Levels and TSLs............................ 9­3

Table 9.2.2 Non­Standard Size Equipment Baseline Efficiency Levels and TSLs.................... 9­4

Table 9.3.1 Existing Federal Energy Conservation Standards for PTACs and PTHPs

(Cooling Mode).................................................................................................... 9­5

Table 9.3.2 ASHRAE/IESNA Standard 90.1­1999 Energy Efficiency Levels for PTACs

and PTHPs (Cooling Mode)................................................................................. 9­6

Table 9.3.3 Energy­Efficiency Equations (EER as a Function of Cooling Capacity) by TSL

for Standards Size PTACs ................................................................................... 9­7

Table 9.3.4 Energy­Efficiency Equations (EER as a Function of Cooling Capacity) by TSL

for Standard Size PTHP....................................................................................... 9­7

Table 9.3.5 Energy­Efficiency Equations for Cooling Mode (EER as a Function of Cooling

Capacity) by TSL for Non­Standard Size PTAC............................................... 9­11

Table 9.3.6 Energy­Efficiency Equations for Cooling Mode (EER as a Function of Cooling

Capacity) by TSL for Non­Standard Size PTHP ............................................... 9­12

Table 9.3.7 Existing Federal Energy Conservation Standards for PTHPs (Heating Mode)..... 9­15

Table 9.3.8 ASHRAE/IESNA Standard 90.1­1999 Energy­Efficiency Levels for PTHPs

(Heating Mode).................................................................................................. 9­16

Table 9.3.9 Energy­Efficiency Equations for Heating Mode (COP as a Function of Cooling

Capacity) by TSL for Standard Size PTHP ....................................................... 9­17

Table 9.3.10 Energy­Efficiency Equations for Heating Mode (COP as a Function of

Cooling Capacity) by TSL for Non­Standard Size PTHP ................................. 9­17
 

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LIST OF FIGURES

Figure 9.3.1 Energy­Efficiency Equations (EER as a Function of Cooling Capacity) by

TSL for Standard Size PTACs and 2008 AHRI Directory Equipment ............... 9­9

Figure 9.3.2 Energy­Efficiency Equations (EER as a Function of Cooling Capacity) by

TSL for Standard Size PTHPs and 2008 AHRI Directory Equipment.............. 9­10

Figure 9.3.3 Energy­Efficiency Equations for Cooling Mode (EER as a Function of

Cooling Capacity) by TSL for Non­Standard Size PTACs and 2008 AHRI

Directory Equipment.......................................................................................... 9­13

Figure 9.3.4 Energy­Efficiency Equations for Cooling Mode (EER as a Function of

Cooling Capacity) by TSL for Non­Standard Size PTHPs and 2008 AHRI

Directory Equipment.......................................................................................... 9­14

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CHAPTER 9. TRIAL STANDARD LEVELS
 

9.1 INTRODUCTION
 

The current Federal minimum energy conservation standards for packaged terminal air

conditioners (PTACs) and packaged terminal heat pumps (PTHPs) and the efficiency

requirements specified by the American Society of Heating, Refrigerating, and Air­Conditioning

Engineers (ASHRAE) and the Illuminating Engineering Society of North America (IESNA)

Standard 90.1­1999, “Energy Standard for Buildings Except Low­Rise Residential Buildings,”

(ASHRAE/IESNA Standard 90.1­1999) are expressed in terms of an energy­efficiency

equations. For the PTAC and PTHP equipment classes with a cooling capacity greater than or

equal to 7,000 British thermal units per hour (Btu/h) and less than or equal to 15,000 Btu/h, the

energy­efficiency equation characterizes the relationship between the energy efficiency ratio

(EER) of the equipment and cooling capacity (i.e., EER is a function of the cooling capacity of

the equipment). For all cooling capacities less than 7,000 Btu/h and all cooling capacities greater

than 15,000 Btu/h, the EER is calculated by substituting either of the two capacities, 7,000 Btu/h

or 15,000 Btu/h, in the energy­efficiency equation. This chapter describes the methodology used

by DOE to derive the energy­efficiency equations for PTAC and PTHP equipment.

9.2 TRIAL STANDARD LEVELS

For the subsequent analyses, DOE refers to the grouping of efficiency levels for each

equipment class as trial standard levels (TSLs). The TSLs are identical to the efficiency levels

examined in the engineering analysis, energy use characterization analysis and the life­cycle cost

(LCC) and payback period analyses (PBP). Table 9.2.1 and For standard size PTACs and

PTHPs, the baseline efficiency levels are the efficiency levels specified by ASHRAE Standard

90.1­1999. TSLs 1, 3, and 5 represent matched pairs of efficiency levels for the two

representative cooling capacities of standard size PTACs and PTHPs. In other words, the

efficiency levels for PTACs and PTHPs with the same cooling capacity and wall sleeve

dimensions are equivalent for these three TSLs. DOE maintained the 0.7 EER decrement

established by ASHRAE Standard 90.1­1999 between the efficiency levels of the standard size

equipment with cooling capacities of 9,000 Btu/h and 12,000 Btu/h. TSL 6 represents the maxtech efficiency levels utilizing R­410A as described in Chapter 5 of the TSD.

After examining preliminary results of the LCC analysis (see Chapter 8 of the TSD),

DOE developed two additional TSLs, TSL 2 and TSL 4, based on the large differences in LCC

savings results between PTACs and PTHPs. TSL 2 and TSL 4 combine different efficiency

pairings between PTACs and PTHPs. In other words, DOE examined the impacts of amended

energy conservation standards when PTACs and PTHPs are required to meet different efficiency

levels. For TSL 2, DOE combined TSL 1 for PTACs and TSL 3 for PTHPs. For TSL 4, DOE

combined TSL 1 for PTACs and TSL 5 for PTHPs. These two combination levels serve to

maximize LCC savings, while recognizing the differences in LCC results for PTACs and PTHPs.

Lastly, DOE added a TSL A in the final rule analysis for standard size PTACs and

PTHPs. TSL A combines the efficiency levels in TSL 3 and TSL 1 for standard size PTACs at

the representative cooling capacities and the efficiency levels in TSL 5 and TSL 3 for standard

size PTHPs at the representative cooling capacities. DOE's inclusion of TSL A recognizes the

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challenge manufacturers encounter when increasing the efficiency of larger cooling capacity

equipment.

Table 9.2.2 present the analyzed efficiency levels as TSLs for standard size and nonstandard size PTACs and PTHPs for the final rule.

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Table 9.2.1 Standard Size Equipment Baseline Efficiency Levels and TSLs
 

Equipment

Class

(Cooling

Capacitya

)

Efficiency

Metricb

Baseline

(ASHRAE/IESNA

Standard 90.1­1999)

TSL

1

TSL

2

TSL

3

TSL

A

TSL

4

TSL

5

TSL 6

(MaxTech)

Standard Size

PTAC EER 10.6 10.9 10.9 11.1 11.1 10.9 11.3 11.5

(9,000 Btu/h)

Standard Size

PTAC EER 9.9 10.2 10.2 10.4 10.2 10.2 10.6 10.8

(12,000 Btu/h)

Standard Size

PTHP

(9,000 Btu/h)

EER

COP

10.4

3.0

10.9

3.1

11.1

3.2

11.1

3.2

11.3

3.3

11.3

3.3

11.3

3.3

11.5

3.3

Standard Size

PTHP

(12,000 Btu/h)

EER

COP

9.7

2.9

10.2

3.0

10.4

3.1

10.4

3.1

10.4

3.1

10.6

3.1

10.6

3.1

10.8

3.1

For standard size PTACs and PTHPs, the baseline efficiency levels are the efficiency

levels specified by ASHRAE Standard 90.1­1999. TSLs 1, 3, and 5 represent matched pairs of

efficiency levels for the two representative cooling capacities of standard size PTACs and

PTHPs. In other words, the efficiency levels for PTACs and PTHPs with the same cooling

capacity and wall sleeve dimensions are equivalent for these three TSLs. DOE maintained the

0.7 EER decrement established by ASHRAE Standard 90.1­1999 between the efficiency levels

of the standard size equipment with cooling capacities of 9,000 Btu/h and 12,000 Btu/h. TSL 6

represents the max­tech efficiency levels utilizing R­410A as described in Chapter 5 of the TSD.

After examining preliminary results of the LCC analysis (see Chapter 8 of the TSD),

DOE developed two additional TSLs, TSL 2 and TSL 4, based on the large differences in LCC

savings results between PTACs and PTHPs. TSL 2 and TSL 4 combine different efficiency

pairings between PTACs and PTHPs. In other words, DOE examined the impacts of amended

energy conservation standards when PTACs and PTHPs are required to meet different efficiency

levels. For TSL 2, DOE combined TSL 1 for PTACs and TSL 3 for PTHPs. For TSL 4, DOE

combined TSL 1 for PTACs and TSL 5 for PTHPs. These two combination levels serve to

maximize LCC savings, while recognizing the differences in LCC results for PTACs and PTHPs.

Lastly, DOE added a TSL A in the final rule analysis for standard size PTACs and

PTHPs. TSL A combines the efficiency levels in TSL 3 and TSL 1 for standard size PTACs at

the representative cooling capacities and the efficiency levels in TSL 5 and TSL 3 for standard

size PTHPs at the representative cooling capacities. DOE's inclusion of TSL A recognizes the

challenge manufacturers encounter when increasing the efficiency of larger cooling capacity

equipment.

a Cooling capacities are expressed in British thermal unit per hour (Btu/h).
 b According to the Air­Conditioning and Refrigeration Institute (ARI) 310/380­2004 Standard for Packaged
 

Terminal Air­Conditioners and Heat Pumps (ARI 310/380­2004) test procedure, energy­efficiency ratio (EER) is
 

defined as “the ratio of the produced cooling effect of an air conditioner or heat pump to its net work input,
 

expressed in Btu/watt­hour.”
 

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Table 9.2.2 Non­Standard Size Equipment Baseline Efficiency Levels and TSLs
 

Equipment

Class

(Cooling

Capacity)

Efficiency

Metricc

Baseline

(ASHRAE/IESNA

Standard 90.1­1999)

TSL

1

TSL

2

TSL

3

TSL

4

TSL

5

(MaxTech)

Non­Standard

Size PTAC EER 8.6 9.4 9.4 9.7 9.4 10.0

(11,000 Btu/h)

Non­Standard

Size PTHP

(11,000 Btu/h)

EER

COP

8.5

2.6

9.4

2.8

9.7

2.8

9.7

2.8

10.0

2.9

10.0

2.9

For non­standard size PTACs and PTHPs, the baseline efficiency levels are the efficiency

levels specified by ASHRAE Standard 90.1­1999. TSLs 1 and 3 represent matched pairs of

efficiency levels for the representative cooling capacity of non­standard size PTACs and PTHPs.

In other words, the efficiency levels for PTACs and PTHPs with the same cooling capacity are

equivalent for these two TSLs. TSL 5 represents the max­tech efficiency levels utilizing R­410A

as described in Chapter 5 of the TSD.

After examining preliminary results of the LCC analysis (see Chapter 8 of the TSD),

DOE developed two additional TSLs, TSL 2 and TSL 4, based on the large differences in LCC

savings results between PTACs and PTHPs. TSL 2 and TSL 4 combine different efficiency

pairings between PTACs and PTHPs. In other words, DOE examined the impacts of amended

energy conservation standards when PTACs and PTHPs are required to meet different efficiency

levels. For TSL 2, DOE combined TSL 1 for PTACs and TSL 3 for PTHPs. For TSL 4, DOE

combined TSL 1 for PTACs and TSL 5 for PTHPs. These two combination levels serve to

maximize LCC savings, while recognizing the differences in LCC results for PTACs and PTHPs.

9.3 ENERGY­EFFICIENCY EQUATIONS

The following sections describe the methodology DOE used to develop the energyefficiency equations for each TSL. To develop the energy­efficiency equations in terms of EER

and cooling capacity, DOE used a linear regression, the efficiency levels for each TSL, or

components of the existing ASHRAE Standard 90.1­1999 energy­efficiency equations.

c Coefficient of performance (COP) is defined by ARI 310/380­2004 as “the ratio of the produced cooling effect of

an air conditioner or heat pump (or its produced heating effect, depending on the mode of operation) to its net work

input, when both the cooling (or heating) effect and the net work input are expressed in identical units of

measurement.”

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9.3.1	 Existing Federal Energy­Efficiency Equations for PTACs and PTHPs and the

Energy­Efficiency Equations in ASHRAE Standard 90.1­1999 in the Cooling Mode

As stated in the engineering analysis (see Chapter 5 of this TSD), current Federal energy

conservation standards and the efficiency levels specified by ASHRAE Standard 90.1­1999 for

PTACs and PTHPs in the cooling mode are a function of the equipment’s cooling capacity. Both

standards specify requirements in the form of energy­efficiency equations to calculate the EER

based on the equipment’s cooling capacity for PTACs and PTHPs with a cooling capacity greater

than or equal to 7,000 Btu/h and less than or equal to 15,000 Btu/h for each equipment class.

Table 9.3.1 and Table 9.3.2 show the current Federal energy conservation standards and

efficiency levels specified by ASHRAE Standard 90.1­1999 for PTACs and PTHPs in the

cooling mode, respectively.

Table 9.3.1 Existing Federal Energy Conservation Standards for PTACs and PTHPs

(Cooling Mode)

Equipment Class Existing Federal

Equipment Cooling Capacity Energy Conservation Standards*

PTAC

<7,000 Btu/h EER = 8.88

>7,000 Btu/h and

<15,000 Btu/h EER = 10.0 – (0.16 x Cap**)

>15,000 Btu/h EER = 7.6

PTHP

<7,000 Btu/h EER = 8.88

>7,000 Btu/h and

<15,000 Btu/h EER = 10.0 – (0.16 x Cap**)

>15,000 Btu/h EER = 7.6

* For equipment rated according to the Air­Conditioning and Refrigeration Institute (ARI) standards, all EER values
 

must be rated at 95oF outdoor dry­bulb temperature for air­cooled products and evaporatively­cooled products and at
 

85oF entering water temperature for water cooled products.
 

** Cap means cooling capacity in kBtu/h at 95oF outdoor dry­bulb temperature.
 

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Table 9.3.2 ASHRAE/IESNA Standard 90.1­1999 Energy Efficiency Levels for PTACs and

PTHPs (Cooling Mode)

Equipment Class Proposed Energy

Conservation Standards* Equipment Category Cooling

Capacity

PTAC

Standard Size**

<7,000 Btu/h EER = 11.0

≥7,000 Btu/h and

≤15,000 Btu/h EER = 12.5 – (0.213 x Cap††)

>15,000 Btu/h EER = 9.3

Non­Standard Size†

<7,000 Btu/h EER = 9.4

≥7,000 Btu/h and

≤15,000 Btu/h EER = 10.9 – (0.213 x Cap††)

>15,000 Btu/h EER = 7.7

PTHP

Standard Size**

<7,000 Btu/h EER = 10.8

≥7,000 Btu/h and

≤15,000 Btu/h EER = 12.3 – (0.213 x Cap††)

>15,000 Btu/h EER = 9.1

Non­Standard Size†

<7,000 Btu/h EER = 9.3

≥7,000 Btu/h and

≤15,000 Btu/h EER = 10.8 – (0.213 x Cap††)

>15,000 Btu/h EER = 7.6

* For equipment rated according to ARI standards, all EER values must be rated at 95oF outdoor dry­bulb

temperature for air­cooled products and evaporatively­cooled products and at 85oF entering water temperature for

water cooled products.

** Standard size refers to PTAC or PTHP equipment with wall sleeve dimensions greater than or equal to 16 inches

high, or greater than or equal to 42 inches wide.

† Non­standard size refers to PTAC or PTHP equipment with wall sleeve dimensions less than 16 inches high and

less than 42 inches wide. ASHRAE/IESNA Standard 90.1­1999 also includes a factory labeling requirement for

non­standard size PTAC and PTHP equipment as follows: “MANUFACTURED FOR REPLACEMENT

APPLICATIONS ONLY; NOT TO BE INSTALLED IN NEW CONSTRUCTION PROJECTS.”

†† Cap means cooling capacity in kBtu/h at 95oF outdoor dry­bulb temperature.

9.3.2	 Revised Energy­Efficiency Equations for Standard Size PTACs and PTHPs in the

Cooling Mode

To derive the energy­efficiency equations corresponding to the various TSLs (i.e.,

efficiency level as a function of cooling capacity) for standard size PTACs and PTHPs, DOE

plotted the representative cooling capacities and the corresponding efficiency levels for each

TSL. DOE then calculated the equation of the line passing through the EER values for 9,000

Btu/h and 12,000 Btu/h for standard size PTACs and PTHPs.

For standard size PTACs and PTHPs with cooling capacity less than 7,000 Btu/h, DOE

determined the corresponding EER value using a cooling capacity of 7,000 Btu/h in the energyefficiency equation. For PTACs and PTHPs with a cooling capacity greater than 15,000 Btu/h

cooling capacity, DOE determined the EER value using a cooling capacity of 15,000 Btu/h in the

energy­efficiency equation. This is the same method established in the Energy Policy Act of

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1992 and provided in ASHRAE Standard 90.1­1999 for calculating the EER and COP of

equipment with cooling capacities smaller than 7,000 Btu/h and larger than 15,000 Btu/h.

Table 9.3.3 and Table 9.3.4 list the equations for the corresponding TSL for standard size

PTAC and PTHP.

Table 9.3.3 Energy­Efficiency Equations (EER as a Function of Cooling Capacity) by TSL

for Standards Size PTACs

Standard Size** PTACs Energy­Efficiency Equation*

Baseline ASHRAE/IESNA Standard 90.1­1999 EER = 12.5 ­ (0.213 x Cap†

/1000)

TSL 1 EER = 13.0 ­ (0.233 x Cap†/1000)

TSL 2 EER = 13.0 ­ (0.233 x Cap†

/1000)

TSL 3 EER = 13.2 ­ (0.233 x Cap†/1000)

TSL A EER = 13.8 ­ (0.300 x Cap†

/1000)

TSL 4 EER = 13.0 ­ (0.233 x Cap†

/1000)

TSL 5 EER = 13.4 ­ (0.233 x Cap†

/1000)

TSL 6 (Max Tech) EER = 13.6 ­ (0.233 x Cap†/1000) * For equipment rated according to the DOE test procedure, all EER values must be rated at 95oF outdoor dry­bulb

temperature for air­cooled products and evaporatively­cooled products and at 85oF entering water temperature for

water cooled products. ** Standard size refers to PTAC or PTHP equipment with wall sleeve dimensions having an external wall opening of

greater than or equal to 16 inches high or greater than or equal to 42 inches wide, and having a cross­sectional area

greater than or equal to 670 inches squared.

† Cap means cooling capacity in Btu/h at 95oF outdoor dry­bulb temperature.

Table 9.3.4 Energy­Efficiency Equations (EER as a Function of Cooling Capacity) by TSL

for Standard Size PTHP

Standard Size** PTHPs Energy­Efficiency Equation*

Baseline ASHRAE/IESNA Standard 90.1­1999 EER = 12.3 ­ (0.213 x Cap†

/1000)

TSL 1 EER = 13.0 ­ (0.233 x Cap†/1000)

TSL 2 EER = 13.2 ­ (0.233 x Cap†

/1000)

TSL 3 EER = 13.2 ­ (0.233 x Cap†

/1000)

TSL A EER = 14.0 ­ (0.300 x Cap†/1000)

TSL 4 EER = 13.4 ­ (0.233 x Cap†

/1000)

TSL 5 EER = 13.4 ­ (0.233 x Cap†

/1000)

TSL 6 (Max Tech) EER = 13.6 ­ (0.233 x Cap†/1000) * For equipment rated according to the DOE test procedure, all EER values must be rated at 95oF outdoor dry­bulb

temperature for air­cooled products and evaporatively­cooled products and at 85oF entering water temperature for

water cooled products. ** Standard size refers to PTAC or PTHP equipment with wall sleeve dimensions having an external wall opening of

greater than or equal to 16 inches high or greater than or equal to 42 inches wide, and having a cross­sectional area

greater than or equal to 670 inches squared.

† Cap means cooling capacity in Btu/h at 95oF outdoor dry­bulb temperature.

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9.3.3	 Rationale for Revised Slope of TSL A for Standard Size PTACs and PTHPs in the

Cooling Mode

DOE further considered the effects of R­410A on system performance for larger cooling

capacities by further investigating the slope of the energy­efficiency equations for standard size

PTACs and PTHPs. DOE found that as a standard size PTAC or PTHP increases in capacity,

manufacturers typically increase the coil surface area or add a coil row to the heat exchanger in

order to increase unit capacity. Manufacturers of standard size PTACs and PTHPs maintain the

same physical box sleeve (i.e., 42 inches by 16 inches) across all models regardless of cooling

capacity. This sleeve size is an established common sleeve size that allows standardization

across the industry. This common sleeve size allows end­users to simply slide replacement units

into existing wall sleeve openings. However, the standard size wall sleeve imposes a limitation

on the total volume available into which all components must fit. Manufacturers add heat

exchanger coil area or coil volume to either increase the cooling capacity or to obtain higher

efficiencies. This fixed volume limits the size of the box into which the unit's components must

fit. In turn, this fixed volume limits the size of heat exchangers and other components that can

be used to increase efficiency and there are accompanying decreases in thermodynamic returns

when making such changes. Thus, higher capacity units often have lower energy efficiency

potentials due to the size constraints of the box sleeve.

In order to consider the effects of the refrigerant phaseout on larger capacity units, DOE

reviewed the market data for standard size equipment in the AHRI Certified Directory. DOE

applied the efficiency degradations distinguished by cooling capacity ranges estimated in the

engineering analysis to each of the models in the AHRI Certified Directory. DOE used these

data to estimate the overall system performance of the models in the AHRI Certified Directory

utilizing R­410A refrigerant. From these data, DOE plotted each TSL it considered as part of the

final rule to see if there were models in the full range of cooling capacity with estimated

performance utilizing R­410A refrigerant that would meet the TSL being considered.

Figure 9.3.1 and Figure 9.3.2 show each energy­efficiency equation plotted for the

various TSLs for standard size PTACs and PTHPs, in addition to the equipment listed in the

2008 AHRI Directory that utilize R­22 and estimated equipment performance with the R­410A

system performance degradations applied.

9­8

 EERE-2007-BT-STD-0012 COMMENT 32
   

   

         

     

     

       

  

                        

                   

EER

Baseline (ASHRAE 90.1­1999)

TSL 1, TSL 2, TSL 4

TSL 3

TSL A

TSL 5

TSL 6 (Max Tech)

R­22 Performance Data (AHRI Directory)

R­410A Estimated Performance Data (Engineering Analysis)

6,000 8,000 10,000 12,000 14,000 16,000 18,000 20,000

Cooling Capacity (Btu/h)

12.5

11.5

10.5

9.5

8.5

7.5

Figure 9.3.1 Energy­Efficiency Equations (EER as a Function of Cooling Capacity) by

TSL for Standard Size PTACs and 2008 AHRI Directory Equipment

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9.0

9.5

10.0

10.5

11.0

11.5

12.0

12.5

EER

Baseline (ASHRAE 90.1­1999)

TSL 1

TSL 2, TSL 3

TSL A

TSL 4, TSL 5

TSL 6 (Max Tech)

R­22 Performance Data (AHRI Directory)

R­410A Estimated Performance Data (Engineering Analysis)

6,000 8,000 10,000 12,000 14,000 16,000 18,000 20,000

Cooling Capacity (Btu/h)

Figure 9.3.2 Energy­Efficiency Equations (EER as a Function of Cooling Capacity) by
 

TSL for Standard Size PTHPs and 2008 AHRI Directory Equipment
 

For TSL A, which is the amended standard level for standard size PTACs and PTHPs,

DOE adjusted the slope of the energy­efficiency equation from the revised slopes calculated for

the NOPR. This adjustment was based on manufacturer comment and DOE data pointing to the

reduced opportunities for achieving greater efficiencies for larger capacity PTAC and PTHP

equipment. By revising the slope in this manner, DOE could create a standard level that is more

stringent for lower cooling capacities, where manufacturers have additional physical space to add

efficiency improvements, but is less stringent for higher cooling capacities, where manufacturers

are physically constrained by the physical dimensions of the box sleeve and less able to

introduce efficiency improvements.

9.3.4	 Revised Energy­Efficiency Equations for Non­Standard Size PTACs and PTHPs in

the Cooling Mode

For non­standard size PTAC and PTHP equipment, DOE used the ASHRAE Standard

90.1­1999 energy­efficiency equation slope and the representative cooling capacity (i.e., 11,000

Btu/h cooling capacity) to develop the energy­efficiency equations representing the entire

cooling capacity range at each TSL. For PTACs and PTHPs with cooling capacity less than

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7,000 Btu/h, DOE determined the corresponding EER value by substituting the cooling capacity

of 7,000 Btu/h in the energy­efficiency equation. For PTACs and PTHPs with a cooling capacity

greater than 15,000 Btu/h cooling capacity, DOE determined the EER value by substituting the

cooling capacity of 15,000 Btu/h in the energy­efficiency equation. This is the same method

established in the Energy Policy Act of 1992 and provided in ASHRAE Standard 90.1­1999 for

calculating the EER and COP of equipment with cooling capacities less than 7,000 Btu/h and

greater than 15,000 Btu/h.

Table 9.3.5 and Table 9.3.6 list the equations for the corresponding TSL for non­standard

size PTAC and PTHP.

Table 9.3.5 Energy­Efficiency Equations for Cooling Mode (EER as a Function of Cooling

Capacity) by TSL for Non­Standard Size PTAC

Non­Standard Size** PTACs Energy­Efficiency Equation*

Baseline ASHRAE/IESNA Standard 90.1­1999 EER = 10.9 ­ (0.213 x Cap†

/1000)

TSL 1 EER = 11.7 ­ (0.213 x Cap†/1000)

TSL 2 EER = 11.7 ­ (0.213 x Cap†

/1000)

TSL 3 EER = 12.0 ­ (0.213 x Cap†/1000)

TSL 4 EER = 11.7 ­ (0.213 x Cap†

/1000)

TSL 5 EER = 12.3 ­ (0.213 x Cap†

/1000) * For equipment rated according to the DOE test procedure, all EER values must be rated at 95oF outdoor dry­bulb

temperature for air­cooled products and evaporatively­cooled products and at 85oF entering water temperature for

water cooled products. ** Non­standard size refers to PTAC or PTHP equipment with existing wall sleeve dimensions having an external

wall opening of less than 16 inches high or less than 42 inches wide, and having a cross­sectional area less than 670

inches squared.

† Cap means cooling capacity in Btu/h at 95oF outdoor dry­bulb temperature.

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Table 9.3.6 Energy­Efficiency Equations for Cooling Mode (EER as a Function of Cooling

Capacity) by TSL for Non­Standard Size PTHP

Non­Standard Size** PTHPs Energy­Efficiency Equation*

Baseline ASHRAE/IESNA Standard 90.1­1999 EER = 10.8 ­ (0.213 x Cap†/1000)

TSL 1 EER = 11.7 ­ (0.213 x Cap†

/1000)

TSL 2 EER = 12.0 ­ (0.213 x Cap†

/1000)

TSL 3 EER = 12.0 ­ (0.213 x Cap†/1000)

TSL 4 EER = 12.3 ­ (0.213 x Cap†

/1000)

TSL 5 EER = 12.3 ­ (0.213 x Cap†/1000) * For equipment rated according to the DOE test procedure, all EER values must be rated at 95oF outdoor dry­bulb

temperature for air­cooled products and evaporatively­cooled products and at 85oF entering water temperature for

water cooled products. ** Non­standard size refers to PTAC or PTHP equipment with existing wall sleeve dimensions having an external

wall opening of less than 16 inches high or less than 42 inches wide, and having a cross­sectional area less than 670

inches squared.

† Cap means cooling capacity in Btu/h at 95oF outdoor dry­bulb temperature.

DOE further considered the effects of R­410A on system performance for larger cooling

capacities by further investigating the slope of the energy­efficiency equations for non­standard

size PTACs and PTHPs. DOE found that as a non­standard size PTAC or PTHP increases in

capacity, manufacturers typically increase the coil surface area or add a coil row to the heat

exchanger in order to increase unit capacity. The fixed volume of the box sleeve imposes a

physical limit on the size of heat exchangers and other unit components that can be used to

increase efficiency. Thus, higher capacity units often have lower energy efficiency potential due

to the size constraints of the box.

In order to consider the effects on larger capacity units, DOE reviewed the market data

for non­standard size equipment in manufacturer equipment catalogs. DOE applied the

efficiency degradations distinguished by cooling capacity ranges estimated in the engineering

analysis to each of the non­standard models offered for sale and described in manufacturer

equipment catalogs. DOE used this data to estimate the overall system performance of the

models on the market utilizing R­410A refrigerant. DOE was able to plot each of the TSLs it

considered as part of the final rule (i.e., TSL 1 through 5) to see if there were models in the full

range of cooling capacities with estimated performance utilizing R­410A refrigerant that would

meet the TSL being considered. These plots demonstrated the specific cooling capacities where

the TSL or amended standard would be eliminating all of the models from the market using the

estimated R­410A performance.

Figure 9.3.3 and Figure 9.3.4 show each equation plotted for the various TSLs for nonstandard size PTACs and PTHPs, in addition to the equipment listed in manufacturers’ catalogs

that utilize R­22 and the estimated performance equipment with the R­410A system performance

degradation applied.

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7.0

7.5

8.0

8.5

9.0

9.5

10.0

10.5

11.0

11.5

12.0

EER

Baseline (ASHRAE 90.1­1999)

TSL 1, TSL 2, TSL 4

TSL 3

TSL 5

R­22 Performance Data (AHRI Directory)

R­410A Estimated Performance Data (Engineering Analysis)

6,000 8,000 10,000 12,000 14,000 16,000 18,000 20,000

Cooling Capacity (Btu/h)

Figure 9.3.3 Energy­Efficiency Equations for Cooling Mode (EER as a Function of Cooling
 

Capacity) by TSL for Non­Standard Size PTACs and 2008 AHRI Directory Equipment
 

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7.0

7.5

8.0

8.5

9.0

9.5

10.0

10.5

11.0

11.5

12.0

EER

Baseline (ASHRAE 90.1­1999)

TSL 1

TSL 2, TSL 3

TSL 4, TSL 5

R­22 Performance Data (AHRI Directory)

R­410A Estimated Performance Data (Engineering Analysis)

6,000 8,000 10,000 12,000 14,000 16,000 18,000 20,000

Cooling Capacity (Btu/h)

Figure 9.3.4 Energy­Efficiency Equations for Cooling Mode (EER as a Function of Cooling

Capacity) by TSL for Non­Standard Size PTHPs and 2008 AHRI Directory Equipment

9.3.5	 Existing Federal Energy­Efficiency Equations for PTACs and PTHPs and the

Energy­Efficiency Equations in ASHRAE Standard 90.1­1999 in the Heating Mode

The current Federal energy conservation standards for PTHPs in the heating mode is

expressed as heating coefficient of performance (COP) as a function of the PTHP’s cooling EER.

Similar to the energy­efficiency equations for PTHPs in the cooling mode, the Federal energy

conservation standards specify COP in the form of an energy­efficiency equation as a function of

EER for PTHPs with a cooling capacity greater than or equal to 7,000 Btu/h and less than or

equal to 15,000 Btu/h. For PTHPs with cooling capacity less than 7,000 Btu/h, the standard is

specified by the COP value corresponding to the EER value for equipment with cooling capacity

of 7,000 Btu/h in the energy­efficiency equation. For PTHPs with a cooling capacity greater

than 15,000 Btu/h, the standard is specified by the COP value corresponding to the EER value

for equipment with cooling capacity of 15,000 Btu/h in the energy­efficiency equation.

The current Federal minimum energy conservation standards for PTHPs in the heating

mode in terms of the COP are presented in Table 9.3.7.

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Table 9.3.7 Existing Federal Energy Conservation Standards for PTHPs (Heating Mode)
 

Equipment Class Existing Federal

Equipment Cooling Capacity Energy Conservation Standards

PTHP

<7,000 Btu/h COP = 2.7

>7,000 Btu/h and

<15,000 Btu/h COP = 1.3 + (0.16 x EER)

>15,000 Btu/h COP = 2.5

The efficiency requirements in ASHRAE Standard 90.1­1999 are specified by energyefficiency equations as a function of the equipment’s cooling capacity for PTHPs with a cooling

capacity greater than or equal to 7,000 Btu/h and less than or equal to 15,000 Btu/h for each

equipment class (i.e., COP is a function of the equipment’s cooling capacity). For PTHPs with

cooling capacity less than 7,000 Btu/h, the standard is determined by the corresponding COP

value by substituting the cooling capacity of 7,000 Btu/h in the energy­efficiency equation. For

PTHPs with a cooling capacity greater than 15,000 Btu/h, the standard is determined by the

corresponding COP value by substituting the cooling capacity of 15,000 Btu/h in the energyefficiency equation.

Table 9.3.8 shows the ASHRAE Standard 90.1­1999 energy­efficiency equations for the

COP of PTHPs.

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Table 9.3.8 ASHRAE/IESNA Standard 90.1­1999 Energy­Efficiency Levels for PTHPs

(Heating Mode)

Equipment Class Proposed Energy

Equipment Category Conservation Standards Cooling

Capacity

PTHP

Standard Size*

<7,000 Btu/h COP = 3.0

≥7,000 Btu/h and

≤15,000 Btu/h COP = 3.2 – (0.026 x Cap†

)

>15,000 Btu/h COP = 2.8

Non­Standard Size**

<7,000 Btu/h COP = 2.7

≥7,000 Btu/h and

≤15,000 Btu/h COP = 2.9 – (0.026 x Cap†

)

>15,000 Btu/h COP = 2.5

* Standard size refers to PTAC or PTHP equipment with wall sleeve dimensions greater than or equal to 16 inches

high, or greater than or equal to 42 inches wide.

** Non­standard size refers to PTAC or PTHP equipment with wall sleeve dimensions less than 16 inches high and

less than 42 inches wide. ASHRAE/IESNA Standard 90.1­1999 also includes a factory labeling requirement for

non­standard size PTAC and PTHP equipment as follows: “MANUFACTURED FOR REPLACEMENT

APPLICATIONS ONLY; NOT TO BE INSTALLED IN NEW CONSTRUCTION PROJECTS.”

† Cap means cooling capacity in kBtu/h at 95oF outdoor dry­bulb temperature.

9.3.6	 Revised Energy­Efficiency Equations for Standard Size and Non­Standard Size

PTACs and PTHPs in the Heating Mode

To maintain consistency with ASHRAE Standard 90.1­1999 and to develop the energyefficiency equations for heating COP, DOE evaluated the COP as a function of cooling capacity.

DOE found the COP based on the linear regressions between EER and COP developed as part of

the engineering analysis. Then, DOE applied the same methodology for deriving the energyefficiency equations as that for the cooling mode. To derive the standard size PTHP energyefficiency equations (i.e., COP as a function of cooling capacity), DOE plotted the representative

cooling capacities and corresponding COP levels for each TSL. For non­standard size PTHPs,

DOE used the ASHRAE Standard 90.1­1999 equation slope and the representative cooling

capacity (i.e., 11,000 Btu/h) to develop the energy­efficiency equations for heating COP that

correspond to the entire cooling capacity range at each TSL.

Table 9.3.9 and Table 9.3.10 list the energy­efficiency equations for COP and the

corresponding TSL for standard and non­standard size PTHP, respectively.

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Table 9.3.9 Energy­Efficiency Equations for Heating Mode (COP as a Function of Cooling

Capacity) by TSL for Standard Size PTHP

Standard Size** PTHPs Energy­Efficiency Equation*

Baseline ASHRAE/IESNA Standard 90.1­1999 COP = 3.2 ­ (0.026 x Cap†/1000)

TSL 1 COP = 3.4 ­ (0.033 x Cap†/1000)

TSL 2 COP = 3.5 ­ (0.033 x Cap†

/1000)

TSL 3 COP = 3.5 ­ (0.033 x Cap†

/1000)

TSL A COP = 3.9 ­ (0.067 x Cap†

/1000)

TSL 4 COP = 3.9 ­ (0.067 x Cap†/1000)

TSL 5 COP = 3.9 ­ (0.067 x Cap†

/1000)

TSL 6 (Max Tech) COP = 3.9 ­ (0.067 x Cap†/1000) * For equipment rated according to the DOE test procedure, all COP values must be rated at 47oF outdoor dry­bulb

temperature for air­cooled products, and at 70oF entering water temperature for water­source heat pumps. ** Standard size refers to PTAC or PTHP equipment with wall sleeve dimensions having an external wall opening of

greater than or equal to 16 inches high or greater than or equal to 42 inches wide, and having a cross­sectional area

greater than or equal to 670 inches squared.

† Cap means cooling capacity in Btu/h at 95oF outdoor dry­bulb temperature.

Table 9.3.10 Energy­Efficiency Equations for Heating Mode (COP as a Function of

Cooling Capacity) by TSL for Non­Standard Size PTHP

Non­Standard Size** PTHPs Energy­Efficiency Equation*

Baseline ASHRAE/IESNA Standard 90.1­1999 COP = 2.9 ­ (0.026 x Cap†

/1000)

TSL 1 COP = 3.1 ­ (0.026 x Cap†

/1000)

TSL 2 COP = 3.1 ­ (0.026 x Cap†

/1000)

TSL 3 COP = 3.1 ­ (0.026 x Cap†

/1000)

TSL 4 COP = 3.2 ­ (0.026 x Cap†/1000)

TSL 5 COP = 3.2 ­ (0.026 x Cap†/1000) * For equipment rated according to the DOE test procedure, all COP values must be rated at 47oF outdoor dry­bulb

temperature for air­cooled products, and at 70oF entering water temperature for water­source heat pumps. ** Non­standard size refers to PTAC or PTHP equipment with existing wall sleeve dimensions having an external

wall opening of less than 16 inches high or less than 42 inches wide, and having a cross­sectional area less than 670

inches squared.

† Cap means cooling capacity in Btu/h at 95oF outdoor dry­bulb temperature.

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