[Code of Federal Regulations]
[Title 10, Volume 3]
[Revised as of January 1, 2006]
From the U.S. Government Printing Office via GPO Access
[CITE: 10CFR431.76]
[Page 416-417]
TITLE 10--ENERGY
CHAPTER II--DEPARTMENT OF ENERGY
PART 431_ENERGY EFFICIENCY PROGRAM FOR CERTAIN COMMERCIAL AND INDUSTRIAL
EQUIPMENT--Table of Contents
Subpart D_Commercial Warm Air Furnaces
Sec. 431.76 Uniform test method for the measurement of energy efficiency
of commercial warm air furnaces.
(a) This Section covers the test procedures you must follow if,
pursuant to EPCA, you are measuring the steady state thermal efficiency
of a gas-fired or oil-fired commercial warm air furnace with a rated
maximum input of 225,000 Btu per hour or more. Where this Section
prescribes use of ANSI standard Z21.47-1998 or UL standard 727-1994,
(Incorporated by reference, see Sec. 431.75), perform only the
procedures pertinent to the measurement of the steady-state efficiency.
(b) Test setup--(1) Test setup for gas-fired commercial warm air
furnaces. The test setup, including flue requirement, instrumentation,
test conditions, and measurements for determining thermal efficiency is
as specified in sections 1.1 (Scope), 2.1 (General), 2.2 (Basic Test
Arrangements), 2.3 (Test Ducts and Plenums), 2.4 (Test Gases), 2.5 (Test
Pressures and Burner Adjustments), 2.6 (Static Pressure and Air Flow
Adjustments), 2.38 (Thermal Efficiency), and 4.2.1 (Basic Test
Arrangements for Direct Vent Control Furnaces) of the ANSI Standard
Z21.47-1998. The thermal efficiency test must be conducted only at the
normal inlet test pressure, as specified in Section 2.5.1 of ANSI
Standard Z21.47-1998, (Incorporated by reference, see Sec. 431.75), and
at the maximum hourly Btu input rating specified by the manufacturer for
the product being tested.
(2) Test setup for oil-fired commercial warm air furnaces. The test
setup, including flue requirement, instrumentation, test condition, and
measurement for measuring thermal efficiency is as specified in sections
1 (Scope), 2 (Units of Measurement), 3 (Glossary), 37 (General), 38 and
39 (Test Installation), 40 (Instrumentation, except 40.4 and 40.6.2
through 40.6.7, which are not required for the thermal efficiency test),
41 (Initial Test Conditions), 42 (Combustion Test--Burner and Furnace),
43.2 (Operation Tests), 44 (Limit Control Cutout Test), 45 (Continuity
of Operation Test), and 46 (Air Flow, Downflow or Horizontal Furnace
Test), of the UL Standard 727-1994. You must conduct a fuel oil analysis
for heating value, hydrogen content, carbon content, pounds per gallon,
and American Petroleum Institute (API) gravity as specified in Section
8.2.2 of the HI BTS-2000 (Incorporated by reference, see Sec. 431.75).
The steady-state combustion conditions, specified in Section 42.1 of UL
Standard 727-1994, (Incorporated by reference, see Sec. 431.75), are
attained when variations of not more than 5 [deg]F in the measured flue
gas temperature occur for three consecutive readings taken 15 minutes
apart.
(c) Additional test measurements--(1) Measurement of flue
CO2 (carbon dioxide) for oil-fired commercial warm air
furnaces. In addition to the flue temperature measurement specified in
Section 40.6.8 of UL Standard 727-1994, (Incorporated by reference, see
Sec. 431.75) you must locate one or two sampling tubes within six
inches downstream from the flue temperature probe (as indicated on
Figure 40.3 of UL Standard 727-1994) (Incorporated by reference, see
Sec. 431.75). If you use an open end tube, it must project into the
flue one-third of the chimney connector diameter. If you use other
methods of sampling CO2, you must place the sampling tube so
as to obtain an average sample. There must be no air leak between the
temperature probe and the sampling tube location. You must collect the
flue gas sample at the same time the flue gas temperature is recorded.
The CO2 concentration of the flue gas must be as specified by
the manufacturer for the product being tested, with a tolerance of
0.1 percent. You must determine the flue
CO2 using an instrument with a reading error no greater than
0.1 percent.
(2) Procedure for the measurement of condensate for a gas-fired
condensing commercial warm air furnace. The test procedure for the
measurement of the condensate from the flue gas under steady state
operation must be conducted as specified in sections 7.2.2.4, 7.8 and
9.2 of the ASHRAE Standard 103-1993 (Incorporated by reference, see
Sec. 431.75) under the maximum rated input conditions. You must conduct
this condensate measurement for an additional 30 minutes of steady state
operation after completion of the steady state thermal efficiency test
specified in paragraph (b) of this section.
[[Page 417]]
(d) Calculations of thermal efficiency--(1) Gas-fired commercial
warm air furnaces. You must use the calculation procedure specified in
Section 2.38, Thermal Efficiency, of ANSI Standard Z21.47-1998
(Incorporated by reference, see Sec. 431.75).
(2) Oil-fired commercial warm air furnaces. You must calculate the
percent flue loss (in percent of heat input rate) by following the
procedure specified in sections 11.1.4, 11.1.5, and 11.1.6.2 of the HI
BTS-2000 (Incorporated by reference, see Sec. 431.75). The thermal
efficiency must be calculated as:
Thermal Efficiency (percent) = 100 percent - flue loss (in percent).
(e) Procedure for the calculation of the additional heat gain and
heat loss, and adjustment to the thermal efficiency, for a condensing
commercial warm air furnace. (1) You must calculate the latent heat gain
from the condensation of the water vapor in the flue gas, and calculate
heat loss due to the flue condensate down the drain, as specified in
sections 11.3.7.1 and 11.3.7.2 of ASHRAE Standard 103-1993,
(Incorporated by reference, see Sec. 431.75), with the exception that
in the equation for the heat loss due to hot condensate flowing down the
drain in Section 11.3.7.2, the assumed indoor temperature of 70 [deg]F
and the temperature term TOA must be replaced by the measured
room temperature as specified in Section 2.2.8 of ANSI Standard Z21.47-
1998 (Incorporated by reference, see Sec. 431.75).
(2) Adjustment to the Thermal Efficiency for Condensing Furnace. You
must adjust the thermal efficiency as calculated in paragraph (d)(1) of
this section by adding the latent gain, expressed in percent, from the
condensation of the water vapor in the flue gas, and subtracting the
heat loss (due to the flue condensate down the drain), also expressed in
percent, both as calculated in paragraph (e)(1) of this section, to
obtain the thermal efficiency of a condensing furnace.
Energy Conservation Standards