Did Panasonic Make a Contractor-Proof Bath Fan?

Ben Hannas -- ben@hannasanalytics.comJonathan Coulter -- jcoulter@advancedenergy.org

Bruce Manclark -- brucemanclark@gorge.net

Data, Not Dogma - July 18-19, 2011 - Goldendale, WA

Measuring Air Flow, Energy Use, and Static Pressure in a Variety of As-Installed Conditions

The Test Setup

Panasonic Whisper GreenFan Controls

• Dial-in CFM• Timer not visible to homeowner

Metering

Variables

• Duct type (metal flex, sheet metal)• Elbow placement (immediate, 2-3’)• Flap (open, screwed shut)• Termination (forced passive, duct roof vent)• Grille (with, without)• Installation type (perfect, small oops, they

probably won’t catch this mistake)

Baseline and Ideal

• Baseline– No duct, open flap, with grille– 136 CFM, 1.5 Pa, 10 Watt

• Ideal– 2 feet straight before elbow, 5 feet

up to roof duct vent termination– 143 CFM, 45 Pa, 19.8 Watt

Duct Type

• No change between metal flex and sheet metal in ideal setup– 141 CFM, 22-24 Pa, 15 Watt

Changing the Termination

• Passive attic vent used as duct termination– Shove it in and seal it– 142 CFM, 22.2 Pa, 14.8 Watt

• Duct roof vent– Meets code– 143 CFM, 45.0 Pa, 19.8 Watt– As a note, running fan 24/7 at this rate is

<$20/year

Real-world Duct Run

• We have a ladder and a phantom truss in the way!– CFM increased

slightly (5 CFM)– Static pressure

doubled to 46 Pa– Energy increased

slightly, up to 21 Watt

Damper

• With the same realistically awkward duct run, now tape the damper shut (but that never happens in real life)– CFM dropped almost in half, but still pulled 87

CFM– Static pressure jumped

from 46 Pa to 128 Pa– Watts increased slightly,

from 21 to 23 Watts

Calibrated Crush

• The “small oops” scenario– Damper open, but complex duct run– No change in CFM– Static increases from

46 Pa to 60 Pa– Watts increase from

21 to 24

Maybe They Won’t Notice

Maybe They Won’t Notice

• Still pulled 57 CFM• 140 Pa• Only 20 Watt