# A:-!DII _I Alr·condltlonlng, Heating, 

# ... _II and Refrigeration Institute
November 19,2012 Dr. DavidDanielson Assistant Secretary for Energy Efficiency and Renewable Energy United States Department ofEnergy 1000 Independence Avenue SW Washington, D.C. 20585 Re: Revision ofAFUE Measurements Calculatedunder CunentU.S. Department of Energy TestProcedures for Two Stage orModulating Condensing Boilers Deal' Assistant Secretary Danielson: 

### An internal audit byAHRI ofthe test results ofproducts tested as part ofAHRI's celiification programs revealed an aspect ofthe current DOE efficiency testprocedures for residential furnaces and boilers that mayresult in an inaccurate AFUE measurement for a subcategory of residential gas boilers. The subcategory is models that are designed to condense and to operate at more than a single inputrate, (i.e., two-stage or modulating condensing boilers). The flaw in the test procedures is inthe calculations used to determine the AFUE whenthe option to skip the heat-up and cool-down tests is selected. Itmust be noted that these ratings were based onthe current DOE efficiency testprocedures, and the enor is due to a flaw in those procedures rather than a failure to properly conduct the DOE test procedure. We want to assure youthat all these models employ condensing technology to achieve the highest efficiencies possible today, so they have AFUEs that exceed the CutTent federal minimum AFUE for these models. The following summarizes the flaw inthe testprocedure: Section 9.10 allows the person conducting the test to omitthe heat-up and cool-down tests for condensing furnaces or boilers which have no measurable air flow through the model during the offcycle. The testprocedure has separate sections specifying the AFUE calculation for condensing furnaces or boilers thathave a single input rate (Section 11.3) and condensing furnaces or boilers that modulate the input rate (Section 11.5). Only Section 11.3 includes alternative calculations to be used when the option allowed by 9.10 is selected (i.e., no heat-up and cool-down tests are conducted). In this case, a
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### I www.ahrinet.orgAHRI Letter to DOE Re: AFUE for Two Step and Modulating Residential Boilers November 19,2012 default draft factor of0.05 is used, and the AFUE is calculatedusing steady state efficiency values. Section 9.10 is an option available to all condensing models that qualify. However, there are no specific calculations in Section 11.5 to detennine the AFUE for a condensing fumace or boiler that modulates the inputrate when the option allowed by 9.10 is selected (i.e. no heat-up and cool-down tests are conducted). In 2001, GAMA developed a Windows

### TMbased AFUE program, which converted the Fortran AFUEprogram developed bythe National Institute ofStandards and Technology (NIST). At thattime, we were advised byNIST ofan error in its program and were provided with a correction for condensing, single input models. Included in the correction was the directionto use "0"for theheat-up and cool-down temperatures inthe Windows

### TMAFUEprogram when the option allowed by Section 9.10 was selected. We have discovered that inserting "0"for heat-up and cool-down temperatures for modulating condensingboilers overestimates the AFUE ofthe model. We are CU1l'ently reviewing the listings for all two-stage and modulating condensing boilers in ourresidential boiler efficiency certificationprogram to determine the full extent ofthis issue. (This may be an issue for residential furnaces as well but our presentinformationis that the heat--up and cool--down tests are always conducted on condensingfurnace models.) Recognizing the significance ofthis matter, we are taking the following actions: • Developing appropriate calculations to determine AFUE for two-stage and modulating condensing boilers thatparallel the corresponding calculation for single inputrate, condensing boilers when the option of9.10 is selected. • Requiring all newmodel celtifications and AHRI certificationtests ofall currently listed models for this subcategory ofboilers to include heat-up and cool-down tests, evenifthe model's AFUE is based on the option allowed by Section 9.10. • Requiring the manufacturers ofall existing models inthis subcategory ofboilers that are listed in our Directory ofCertified Product Performance to do one ofthe following: 

### (1) drop the rating to 90%; (2) discontinue the model; or (3) providetests results which include the heat-up and cool-down tests that support a higher rating. We are implementing this immediately. By mid-December 2012, we will provide to DOE a suggested AFUE calculation for two-stage and modulating condensing boilers when the option of9.10 is used, and will request its expeditedreview and adoption. We are available to meet with DOE staffto explainthe derivation ofthis calculation. Once this altemative calculation is accepted and the manufacturer provides newtest data using the altemative calculation, the ratings for those models where option 1 was selected will berevised, and discontinued models will berestored withrevised ratings. 

### 2ARRI Letter to DOERe: AFUE for Two Step and Modulating Residential Boilers November 19, 2012 We also recommend that DOE immediately notify other manufacturers ofmodulating condensingboilers that are not part ofthe ARRI certificationprogram (Allied Engineering CompanyDiv. ofE·Z·RectManufacturing Ltd; Baxi Spa; Conematic Heating Systems Inc.; HamiltonEngineering; NavienAmerica Inc.; Quietside; and Quincy Hydronic Technologies) of this en'Qf inthe DOEtest procedure, andrequire themto take immediate actions to ensure the accurate rating oftheir equipment. AHRI is committed to working with DOEto resolve this issue as expeditiously as possible. Sincerely, Stephen 

### R. Yur President and CEO Air·Conditioning, Heating, and Refrigeration Institute (ARRI)
cc: Timothy G. Lynch John Cymbalsky

3Residential High-Efficiency BoilerAFUE Ratings Meetingwith DOE and AHRI
November 19, 2012

DOE Test Procedure (ASH RAE 103) - Equipment Classification

Section 9.10 applies 11/19/2012

1DOE Test Procedure (ASH RAE 103) - Summary of tests I> For all equipment

- Steadv-state efficiencv test

- Part-load efficiency test • Cool-down test Section 9.10

- Tracer gas test (optional) Required P'LAHRI to apply Section 9.10 I>- For condensing equipment

- Condensate collection test at steady-state and during heat-up cooldown tests I> For modulating equipment

- Repeat all applicable tests for maximum fire and minimum fire



### DOE Test Procedure (ASHRAE 103)

Section 9.10 applies 

### 11/19/2012

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### NIST AFUE Program and GAMAAFUE Calculator

,.. Program Developed by NIST - A graphical user interface was developed by GAMA 17 When option 9.10 was selected for condensing equipment

- Instructed to enter zeroes for heat-up and cool-down tests

.. Calculated Results:

- Accurate for condensing/non-modulating equipment

- Not-accurate for condensing/modulating equipment • Causes AFUE to be over stated by 1 to 4 percent



### AHRI Actions - Effective Immediately l>- Requiring**heat~up** and cool-down testingfor condensing, modulating equipmentfor qualification and verification testing, even ifthe model's AFUE is based on the option allowed bySection 9.10. .,. Requiring the manufacturers of all existing models In this subcategory of boilers listed in AHRi Oirectory ofCertified Product Performanceto do one of the following:

- Drop the rating to 90%;

- Discontinue the model; or

- Provide test results including the heat-up and cool-down tests, which support a higher rating. P- Developing appropriate calculations to determineAFUE for two-stage and modulating condensing boilers that parallel the corresponding calculation for single input rate, condensing boilers whenthe option of9.10 is selected. 11/19/2012



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