1 

# IEER Differential

Additional Work on Gas Furnace IEER Differential

• Gas furnace pressure drop based on product literature: Carrier, Trane,

Lennox. Furnace pressure drop information not provided for other brands.

• For some products, gas furnace pressure drop is directly listed.

• For others, calculate difference between no

- heat product ESP and gas

- heat

ESP for the rated air flow rate and identical fan speed (rpm).

• For key nominal capacities (previously selected for adapter curb analysis),

determine typical gas furnace pressure drop:

– Determine gas furnace pressure drop for available models.

– Average over available models at each nominal capacity for each manufacturer

(e.g. low, high, highest efficiency). Drop highest efficiency in averaging if the

pressure drop is unusually low.

– Average the manufacturer averages for each nominal capacity.

– Average the nominal capacity averages for each class.



## • Apply gas pressure drop of the class to IEER calculations developed during

the engineering analysis to determine IEER impact.2 

# Gas Furnace Pressure Drop

Average Furnace Pressure Drop [in WG]

Capacity Shipment

Percentage Mfgr 1 Mfgr 2 Mfgr 3 Nominal

Capacity Average

6 20.8% 0.07 0.13 0.09 0.09

7.5 18.2% 0.11 0.10 0.07 0.09

8.5 16.4% 0.17 0.14 0.10 0.14

10 13.8% 0.19 0.20 0.13 0.17

12.5 9.4% 0.20 0.24 0.04 0.16

15 5.0% 0.12 0.19 0.05 0.12

17.5 3.7% 0.16 0.28 0.07 0.17

20 3.3% 0.19 0.24 0.07 0.17

25 2.6% 0.27 0.38 0.10 0.25

27 2.3%

- 0.11 0.06 0.09

30 1.8% 0.39 0.24 0.10 0.24

35 1.1% 0.05 0.36 0.11 0.17

40 0.4% 0.05 0.48 0.09 0.21

45 0.4% 0.05

- - 0.05

50 0.4% 0.05 0.86 0.23 0.38

55 0.4%

- 1.85 0.16 1.01

60 0.4%

- 1.23 0.17 0.70



# Average gas furnace pressure drop developed based on equal

manufacturer market share and shipment distribution by

capacity used for curb adapter analysis

.

Equipment

Class Average Furnace

Pressure Drop [in WG]

Small 0.12

Large 0.15

Very large 0.253 

# IEER Differential

• Recalculate IEER for the selected energy modeling units based

on class average gas furnace pressure drop.

• Increased indoor fan power base on fan power tables.

7.5

- ton 15

- ton 30

- ton

EL IEER Difference EL IEER Difference EL IEER Difference

Baseline_single comp.

- 0.18 Baseline

- 0.41 Baseline

- 0.31

Baseline_dual comp.

- 0.22 Path

- 1

- EL

- 1

- 0.34 Path

- 1

- EL

- 1

- 0.36

Path

- 1

- EL

- 1

- 0.32 Path

- 2 EL1

- 0.20 Path

- 2 EL1

- 0.18

Path

- 2 EL1

- 0.23 Path

- 1

- EL

- 2

- 0.36 Path

- 1

- EL

- 2

- 0.58

Path

- 1

- EL

- 2

- 0.20 Path

- 2 EL2

- 0.16 Path

- 2 EL2

- 0.13

Path

- 2 EL2

- 0.26 EL2.5

- 0.23 Path

- 1 EL2.5

- 0.51

EL2.5

- 0.13 EL

- 3

- 0.22 Path

- 2 EL2.5

- 0.08

EL

- 3

- 0.13 EL

- 3.5

- 0.21 EL

- 3

- 0.14

EL

- 3.5

- 0.10 EL

- 4

- 0.28 EL

- 4

- 0.19

EL

- 4

- 0.36 EL

- 5

- 0.33 EL

- 5

- 0.29

EL

- 5

- 0.14 Average

- 0.27 Average

- 0.28

Average

- 0.21 Max

- 0.16 Max

- 0.08

Max

- 0.10 Min

- 0.41 Min

- 0.58

Min

- 0.36 Standard Deviation 0.08 Standard Deviation 0.17

Standard Deviation 0.08

Note: IEER differential is the absolute value difference for IEER,

not difference by percentage.