1

Appliance Standards g uidance documents are accessible on the U.S. Department of Energy, Energy Efficiency & Renewable Energy web site at: http://www1.eere.energy.gov/guidance/default.aspx?pid=2&spid=1

.

Guidance Type: Enforcement Category: Commercial Equipment Product: Small, Large, and Very Large, Air

- Cooled, Water

- Cooled, and Evaporatively

- Cooled Commercial Package Air Conditioners and H eat Pumps, Water

- Source Heat Pumps, Single Package Vertical Units, and Computer Room Air Conditioners Product Sub

- type: All Guidance Version: DRAFT Issued: June 29, 2015 Comment Period Ends: July 29, 2015

The following is a draft U.S. Department of Energy (DOE or the Department) document regarding how to evaluate whether small, large, and very large air

- coole d , water

- cooled, and e vaporatively

- cooled commercial package air conditioners and heat pumps, water

- source heat pumps, single package vertical units, and computer room air conditioners offered for sale with a variety of h igh static indoor blower or oversized motor to qualif y for a related DOE enforcement policy

. This draft document is seeking comment regarding the best way to effectuate an enforcement policy and is not an interpretation of DOE’s regulations.

Comments and suggestions should be provided in WordPerfect, Microsoft Word, PDF, or text file format by sending an email to ComHVACMotorGuidance@ee.doe.gov

. Please also include the docket number EERE

- 2015

- BT

- GUID

- 0011 . At the end of the comment period, this draft document may be adopted or revised

.
During a negotiated rulemaking regarding Certification for Commercial Heating, Ventilation, Air

Conditioning, Water

- Heating, and Refrigeration Equipment , DOE agreed to adopt an enforcement policy under which DOE would not test a model of HVAC equipment with a high

- static indoor blower or over

sized motor provided (1) the manufacturer offers an ot herwise equivalent model that contains a “standard motor” and (2) the high static indoor blower/oversized motor ha s the same (or better) relative efficiency performance as the “standard motor ” . Due to time constraints in the negotiation, the parties did n ot define how to compare the efficiencies of motors for the purposes of this policy , but the parties did talk through and agree to the concept broadly . Instead, the parties agreed DOE would issue guidance to resolve that issue after accepting additional c omment on the details of the procedure

.
DOE proposes the following approach to compare the efficiencies of a “standard motor” and a high

static indoor blower/oversized motor (“oversized motor”) :

Standard Motor Oversized Motor OK to substitute oversized motor? (DOE would not test a unit with the oversized motor.) Subject to standards Can be tested with DOE TP Subject to standards Can be tested with DOE TP Yes, if relative efficiency of oversized motor is at least as good as performance of standard motor Subject to standards Not subject to standards Yes, if relative efficiency of oversized motor is at2

Can be tested with DOE TP Can be tested with DOE TP least as good as performance of standard motor Not subject to standards Can be tested with DOE TP Subject to standards Can be tested with DOE TP Yes, if relative efficiency of oversized motor is at least as good as performance of standard motor Not subject to standards Can be tested with DOE TP Not subject to standards Can be tested with DOE TP Yes, i f relative efficiency of oversized motor is at least as good as performance of standard motor Subject to standards Can be tested with DOE TP Not subject to standards Cannot be tested with DOE TP but can be tested with industry method Cannot substitute ove rsized motor

Not subject to standards Can be tested with DOE TP Not subject to standards Cannot be tested with DOE TP but can be tested with industry method Cannot substitute oversized motor

Not subject to standards Cannot be tested with DOE TP but can be tested with industry method Not subject to standards Cannot be tested with DOE TP but can be tested with industry method Yes, if relative efficiency of oversized motor is at least as good as performance of standard motor

– and both motors are tested usi ng same industry method No standard test method No standard test method Cannot substitute oversized motor Motors with horsepower < 1 Motors with horsepower < 1 Cannot substitute oversized motor

Motors with horsepower < 1 Motors with horsepower ≥ 1 Cannot substitute oversized motor

Determining relative efficiency of the motor

C ompare the percent losses of the standard motor to the percent losses of the oversized motor. The percent losses in a standard or oversized motor are determined by comparing each motor’s wattage los ses to the wattage losses of a corresponding reference motor. Although DOE appreciates that a variety of motor sizes, construction, and purposes are used in HVAC equipment, the HVAC members of the Commercial Certification Working Group stated that it was unfamiliar with the standards tables for electric motors and recommended that DOE should adopt a relatively simple way for DOE to implement its enforcement policy with respect to motor substitution. Accordingly, DOE does not believe that the reference motors need to reflect such a level of granularity because the motors generally scale in a similar manner

.
The F ederal standard levels for 4 pole, open frame, general purpose electric motors ( subtype I ) ( see 10 CFR 431.25(a) ) would be used to scale the performance of the standard motor to an oversized motor whether the motor s are subject to F ederal standard levels or not. Use the following steps to determine if an oversized motor is a suitable substitute for the standard moto r for the purposes of DOE’s enforcement policy

. 1

1 Note, that 10 CFR 429.71 requires manufacturers to retain documentation supporting its certifications of compliance. Accordingly, any manufacturer using this methodology is required to maintain documentation of how the standard and oversized motor’s losses were determined and the supporting calculations specified below to demonstrate that it had ensured the substituted motor is authorize d under the enforcement policy.3

1. Using the tested efficiency of the standard motor, determine the wattage losses of the standard
motor (Loss std ) with the following equation, where η std is the tested e fficiency of the standard motor and hp std is the horsepower of the standard motor :

Loss std = 746 ∗ h p std ∗ 1

− η std η std

2. Determine the appropriate reference motor efficiency corresponding to the standard motor (standard motor reference efficiency, η rs ) . Using the F ederal stand ard levels for 4 pole, open frame, general purpose electric motors ( subtype I ) in 10 CFR 431.25(a)
, look up the efficiency level that corresponds to the standard motor ’s horsepower

.

3. Using the standard reference motor efficiency, determine the percent losses of the standard reference motor (Loss rs ) with the following equation, where η rs is the standard reference motor efficiency and hp rs is the horsepower of the standard ref erence motor (hp rs is e qui vale nt to the horsepower of the standard motor):

Loss rs = 746 ∗ h p rs ∗ 1

− η rs η rs

4. With the wattage losses for both the standard motor and the standard reference motor, calculate the percentage losses of the standard motor as follows:

% Loss = 100 ∗ ( Loss rs − Loss std )
Loss rs

5. Determine the appropriate reference motor efficiency corresponding to the oversized motor (oversized motor reference efficiency, η ro ). Using the F ederal standard levels for 4 pole, open frame, general purpose ele ctric motors ( subtype I ) in 10 CFR 431.25(a) , look up the efficiency level that corresponds to the oversized motor ’s horsepower.

6. Using the oversized reference motor efficiency, determine the percent losses of the oversized reference motor (Loss ro ) with the following equation, where η ro is the oversized reference motor efficiency and hp ro is the horsepower of the oversized reference motor (hp ro is equivalent to the horsepower of the oversized motor):

Loss ro = 746 ∗ h p ro ∗ 1

− η ro η ro

7. With the wattage losses for the oversized reference motor (Loss ro ) and the percent losses of the standard motor (%Loss) , determine the allowable losses in watts f or the oversized motor.

Allowable Losses = ( 1

− % Loss ) ∗ Loss ro

8. From the allowable losses, the minimum efficiency for the oversized motor ( η o ) can be calculated according to the following equation , where hp o is the horsepower for the oversized motor.

η o = 100 ∗ ( h p o ∗ 746 )

( h p o ∗ 746 + Allowable Losses )4

9. The oversized motor is an acceptable substitute for the standard motor if th e tested efficiency of the oversized motor is greater than or equal to η o .

Example : A basic model commercial air conditioner was rated with a 5hp motor that has an efficiency of
91.7%. If a manufacturer wants to sell this basic model commercial air conditioner with a 10hp motor as well , w hat is the minimum efficiency required for the 10hp motor ?

The standard motor for this basic model of commercial air conditioner is the 5hp with an efficiency of 91.7% . The wattage losses of the standard motor are:

Loss std = 746 ∗ h p std ∗ 1

− η std η std = 746 ∗ 5h p ∗ 1

− 0

. 917 0

. 917 = 337

. 6 W

T he reference motor efficiency corresponding to the standard motor is determined by look ing up the appropriate value based on the standard motor ’ s horsepower in the Federal standard levels for 4 pole, open frame, general purpose electric motors ( subtype I ) in 10 CFR 431.25(a) . T he reference efficiency for 5 hp motor is 89.5% . 10 CFR 431.25(a) . The standard reference efficiency is used to calculate the wattage losses for the standard reference motor.

Loss rs = 746 ∗ h p rs ∗ 1

− η rs

η rs = 746 ∗ 5h p ∗ 1

− 0

. 895

0

. 895 = 437

. 6 W

Using the wattage losses for the standard motor and standard reference motor, calculate the percent losses.

% Loss = 100 ∗ ( Loss rs − Loss std )
Loss rs = 100 ∗ ( 437

. 6

− 337

. 6 )
437

. 6 = 22

. 8%

Therefore, if a manufacturer wants to use a 10h p oversized mo tor in this commercial air conditioner basic model then the oversized motor must have at least 22.8% fewer losses than the corresponding oversized reference motor

. The efficiency of the oversized reference motor can be found by looking up the efficiency f or a 10hp in the Federal standard levels for 4 pole, open frame, general purpose electric motors ( subtype I ) in 10 CFR 431.25(a) . The oversized reference motor efficiency for the 1 0hp motor is 91.7%. (10 CFR 431.25(a)) Calculate the oversized reference mo tor’s wattage losses from the efficiency of the oversized reference
motor :

Loss ro = 746 ∗ h p ro ∗ 1

− η ro

η ro = 746 ∗ 10h p ∗ 1

− 0

. 917 0

. 917 = 675

. 2 W

Then determine the allowable losses in watts for the oversized motor.

Allowable Losses = ( 1

− % Loss ) ∗ Loss ro = ( 1

− 0

. 228 ) ∗ 675

. 2 W = 521

. 3 W
Finally, determine the acceptable minimum efficiency for the oversized motor.

η o = 100 ∗ ( h p o ∗ 746 )

( h p o ∗ 746 + Allowable Losses ) = 100 ∗ ( 10h p ∗ 746 ) ( 10h p ∗ 746 + 521

. 3 W ) = 93

. 5%5

In summary, a 10hp motor wi th a minimum efficiency of 93.5% is an acceptable substitute for a 5hp standard motor with 91.7% efficiency according to DOE’s propose enforcement policy.
Acceptable 10h p motor efficiency ≥ η o
93.5% > 91.7% ∴ substitution perm itted