7.6-i APPENDIX 7.6. OVERALL AIR-MOVING EFFICIENCY TABLE OF CONTENTS 7.6.1 INTRODUCTION ................................................... 7.6-1 7.6.2 RESULTS ......................................................... 7.6-5 LIST OF TABLES Table 7.6.2.2 Coefficients for Overall Air-Moving Efficiency of Condensing Generic Model Furnaces ........................................ 7.7-6 LIST OF FIGURES Figure 7.6.1.1 Overall Air-Moving Efficien cy (non-condensing, cooling mode) ........ 7.6-2 Figure 7.6.1.2 Overall Air-Moving Efficiency (non-condensing, low-fire mode) ........ 7.6-2 Figure 7.6.1.3 Overall Air Moving Efficien cy (non-condensing, heating mode) ......... 7.6-3 Figure 7.6.1.4 Overall Air-Moving Efficiency (condensing, cooling mode) ............ 7.6-3 Figure 7.6.1.5 Overall Air Moving Efficiency (condensing, heating mode) ............ 7.6-4 Figure 7.6.1.6 Overall Air-Moving Efficien cy (condensing, low-fire mode) ............ 7.6-47.6-1 APPENDIX 7.6. OVERALL AIR-MOVING EFFICIENCY 7.6.1 INTRODUCTION The overall air-moving efficiency is a variable in the calculation of blower motor electricity consumption. The overall air-moving efficiency is a ratio of the air power divided by the electric power used by the blower motor. Air power is the power embodied in the air due to its motion and pressure increase. Air power at any operating condition can be calculated for any furnace from pressure, airflow, and supply air outlet area, as explained in Chapter 7, section 7.5.3, Overall Air-Moving Efficiency. In addition to the pressure and airflow data that are available for all furnace models, one manufacturer reports fan motor electricity consumption as well. 1, 2, 3, 4, 5, 6 The model series used for these calculations are Lenox G23 and G40 for non-condensing furnaces and Lenox 90UGF, G26Q, and GHR26Q for condensing furnaces. For these models, DOE calculated air power and overall efficiency for each point in the fan operating tables for each of the models. The relationships between air power and overall efficiency are only valid for these particular furnace models and vary by airflow capacity. To generalize the relationship of overall air-moving efficiency to airflow in order to cal culate efficiency for any furnace type, the Department transformed airflow to a percentage of airflow at free flow. Free flow signifies no pressure difference or drop. The free flow percen tage transformation allowed all of the curves to be plotted together independently of cfm measurement. Figures 7.6.1.1 through 7.6.1.6 show the overall air-moving efficiency as a function of airf low, where airflow is indicated as fraction of free flow.7.6-2 0% 5% 10% 15% 20% 25% 30%

40% 50% 60% 70% 80% 90% 100% Airflow (as percent of free flow)Overall Air Moving Efficiency

Lennox Series G23 & G40 Cooling Data Predicted Efficiency
Figure 7.6.1.1 Overall Air-Moving Efficiency (non-condensing, cooling mode)

0% 5% 10% 15% 20% 25% 30%

40% 50% 60% 70% 80% 90% 100% Airflow (as percent of free flow)Overall Air Moving Efficiency

Lennox Series G23 & G40 Low Fire Heating Data Predicted Efficiency
Figure 7.6.1.2 Overall Air-Moving Efficiency (non-condensing, low-fire mode)7.6-3 0% 5% 10% 15% 20% 25% 30%

40% 50% 60% 70% 80% 90% 100% Airflow (as percent of free flow)Overall Air Moving Efficiency

Lennox Series G23 & G40 High Fire Heating Data Predicted Efficiency
Figure 7.6.1.3 Overall Air Moving Efficiency (non-condensing, heating mode)

0% 5% 10% 15% 20% 25% 30%

40% 50% 60% 70% 80% 90% 100% Airflow (as percent of free flow)Overall Air Moving Efficiency

Lennox Series 90UGF, G26Q, & GHR26Q Cooling Data Predicted Efficiency Figure 7.6.1.4 Overall Air-Moving Efficiency (condensing, cooling mode)7.6-4 0% 5% 10% 15% 20% 25% 30%

40% 50% 60% 70% 80% 90% 100% Airflow (as percent of free flow)Overall Air Moving Efficiency

Lennox Series 90UGF, G26Q, & GHR26Q High Fire Heating Data Predicated Efficiency
Figure 7.6.1.5 Overall Air Moving Efficiency (condensing, heating mode)

0% 5% 10% 15% 20% 25% 30%

40% 50% 60% 70% 80% 90% 100% Airflow (as percent of free flow)Overall Air Moving Efficiency

Lennox Series 90UGF, G26Q, & GHR26Q Low Fire Heating Data Predicted Efficiency
Figure 7.6.1.6 Overall Air-Moving Efficiency (condensing, low-fire mode)7.6-5 Also shown in each figure is a single curve that best fits the other curves in each plot. The Department fit these curves to an equation of overall efficiency as a function of the ratio of airflow to free airflow. The form of the equation was selected to match the general trends of the overall efficiency curves of the specific models. The Department found the best fit between the data points from the manufacturers' literature and the equation by adjusting the coefficients to minimize the root-mean-square error in overall efficiency. 

## () () ( ) 

## ( ) ( ) η overall c c Q c Q c Q = + ×− + ×− + ×− 0 11 0 21 0 1/2 31 0 1/3 where: = overall air-moving efficiency, η overal l = ratio of airflow to free flow, and 

### Q 0 = empirically determined coefficients. 

### cccc

0123



### ,,, 7.6.2 RESULTS The Department calculated the results separately for condensing and non-condensing furnaces, and for each model. The coefficients for the six equations are shown in Tables 7.6.2.1 and 7.6.2.2. Table 7.6.2.1 Coefficients for Overall Air-Moving Efficiency of Non-Condensing Generic Model Furnaces Cooling Heating Low-Fire Coef0 0.015169 .0096357 0.010040 Coef1 -0.21144 -0.49263 -0.75554 Coef2 0.91056 1.1948 1.4069 Coef3 -0.39518 -0.42712 -0.49662 Table 7.6.2.2 Coefficients for Overall Air-Moving Efficiency of Condensing Generic Model Furnaces Cooling Heating Low-Fire Coef0 0.012659 0.0090140 0.0079380 Coef1 -0.74379 -0.94689 -0.90500 Coef2 1.7392 1.8971 1.7061 Coef3 -0.83602 -0.79362 -0.654377.6-6 REFERENCES 1. Lennox Industries Inc., Lennox Engineering Data: G26 (Elite 90 Series Upflow Gas Furnace), Bulletin #210027, 1998. Lennox Industries Inc. 2. Lennox Industries Inc., Lennox Engineering Data: GHR26 (Elite 90 Series Horizontal/Downflow Gas Furnace) Bulletin # 210093, 1998. Lennox Industries, Inc. 3. Lennox Industries Inc., Lennox Industries Engineering Data: 90UGF (Elite 90-S Upflow Gas Furnace) Bulletin #210171., 1997. Lennox Industries Inc. 4. Lennox Industries Inc., Lennox Engineering Data: G23 (Elite 80 Upflow Gas Furnace) Bulletin #210026, 1998. Lennox Industries Inc. 5. Lennox Industries Inc., Lennox Engineering Data: G40DF (Merit Series Downflow Gas Furnace) Bulletin No. 210320., 2002. Lennox Industries, Inc. (Last accessed July, 2003). <http://www.lennoxcommercial.com/tech_pdf/ehb_g40df_0206.pdf> 6. Lennox Industries Inc., Lennox Engineering Data: G40UH (Merit Series Upflow/Horizontal Gas Furnace) Bulletin No. 210320., 2002. Lennox Industries, Inc. (Last accessed July, 2003). <http://www.lennoxcommercial.com/tech_pdf/ehb_g40uh_0206.pdf>