Blower Door Technical Notes

INDEX OF NOTES:
• Calibration formulas for Infiltec E3 fans
• Calibration formulas for Infiltec R2 fans
• High pressure performance fan curves for E3 fans
• Can't Reach 50 Pa table for any blower door

Infiltec E3 Blower Door High Pressure Fan Performance Curves

EQUIPMENT: E3 Fan with standard blade A.
DATE & LOCATION: August 1997 - Infiltec factory calibration test chamber.
NOTE: Preliminary data - not corrected for ~1500 ft altitude.

INFILTEC E3 FAN CURVE DATA

Calibration formulas for Infiltec E3 fans

Q is fan flow in cfm, P is fan flow pressure in "wc, SQR() is square root, * is multipy
E3 Formulas:
Q is fan flow,
P is fan flow pressure,
SQR() is square root,
* is multiply.
The E3 low flow plate has 7 holes, including a center hole.
The standard E3 Magnahelic flow gauges are calibrated in cfm with two scales: the top scale is for the open fan (no low-flow plate), and the bottom scale is for the low-flow plate installed with all 7 holes open. When the low-flow plate is installed on the fan, and some of the holes are plugged, then divide the lower cfm scale on the Magnahelic flow gauges by the Plate Factor specificed below. There is an optional E3 Magnahelic gauge calibration in m3/s rather than cfm.

For units of Q in cfm and P in "wc:
Q=6360*SQR(P): flow with no plate on fan (e.g. 6360 cfm @ 1"wc), read upper flow scales on Magnahelic flow gauges.
Q=1632*SQR(P): flow with low-flow plate on fan, all 7 holes open, read lower flow scales on Magnahelic flow gauges, Plate Factor = 1.0.
Q=965*SQR(P): flow with low-flow plate on fan, 4 holes open, read lower flow scales on Magnahelic flow gauges, Plate Factor = 1.69.
Q=704*SQR(P): flow with low-flow plate on fan, 3 holes open, read lower flow scales on Magnahelic flow gauges, Plate Factor = 2.32.
Q=442*SQR(P): flow with low-flow plate on fan, 2 holes open, read lower flow scales on Magnahelic flow gauges, Plate Factor = 3.68.
Q=171*SQR(P): flow with low-flow plate on fan, 1 center hole open, read lower flow scales on Magnahelic flow gauges, Plate Factor = 9.52.

For units of Q in cfm and P in Pa:
Q=403.0*SQR(P): flow with no plate on fan (e.g. 403.0 cfm @ 1 Pa), read upper flow scales on Magnahelic flow gauges.
Q=103.4*SQR(P): flow with low-flow plate on fan, all 7 holes open, read lower flow scales on Magnahelic flow gauges, Plate Factor = 1.0.
Q=61.1*SQR(P): flow with low-flow plate on fan, 4 holes open, read lower flow scales on Magnahelic flow gauges, Plate Factor = 1.69.
Q=44.6*SQR(P): flow with low-flow plate on fan, 3 holes open, read lower flow scales on Magnahelic flow gauges, Plate Factor = 2.32.
Q=28.0*SQR(P): flow with low-flow plate on fan, 2 holes open, read lower flow scales on Magnahelic flow gauges, Plate Factor = 3.68.
Q=10.83*SQR(P): flow with low-flow plate on fan, 1 center hole open, read lower flow scales on Magnahelic flow gauges, Plate Factor = 9.52.

Calibration formulas for Infiltec R2 fans

R2 Formulas:
Q is fan flow,
P is fan flow pressure,
SQR() is square root,
* is multiply.
The R2 low flow plate has 7 holes, including a center hole.
The R2 Magnahelic flow gauge is calibrated in cfm and lps for the open fan (no low-flow plate). When the low-flow plate is installed on the fan, divide the Magnahelic flow gauge cfm by the Plate Factor specificed below.

For units of Q in cfm and P in "wc:
Q=4860*SQR(P): flow with no plate on fan (e.g. 4860 cfm @ 1"wc), Plate Factor = 1.0.
Q=2371*SQR(P): flow with low-flow plate on fan, all 7 holes open, Plate Factor = 2.05.
Q=1328*SQR(P): flow with low-flow plate on fan, 4 holes open, Plate Factor = 3.66.
Q=621*SQR(P): flow with low-flow plate on fan, 2 holes open, Plate Factor = 7.82.
Q=279*SQR(P): flow with low-flow plate on fan, 1 hole open (center), Plate Factor = 17.4.

For units of Q in cfm and P in Pa":
Q=307.9*SQR(P): flow with no plate on fan (e.g. 307.9 cfm @ 1 Pa), Plate Factor = 1.00.
Q=150.2*SQR(P): flow with low-flow plate on fan, all holes open, Plate Factor = 2.05.
Q=84.1*SQR(P): flow with low-flow plate on fan, 4 holes open, Plate Factor = 3.66.
Q=39.4*SQR(P): flow with low-flow plate on fan, 2 holes open, Plate Factor = 7.82.
Q=17.7*SQR(P): flow with low-flow plate on fan, 1 holes open(center), Plate Factor = 17.4.

Can't Reach 50 Pa table for any blower door

Sometimes the building is so leaky that the maximum blower
door flow is not enough to get to 0.200 in.wc (50 Pa) pressure.
You can use the table below to calculate the 50 Pa flow:

Max pressure = 0.200 in.wc (50 Pa), then multiply flow by 1.00 for 50 Pa flow.
Max pressure = 0.175 in.wc (43.6 Pa), then multiply flow by 1.09 for 50 Pa flow.
Max pressure = 0.150 in.wc (37.4 Pa), then multiply flow by 1.20 for 50 Pa flow.
Max pressure = 0.125 in.wc (31.1 Pa), then multiply flow by 1.36 for 50 Pa flow.
Max pressure = 0.100 in.wc (24.9 Pa), then multiply flow by 1.57 for 50 Pa flow.
Max pressure = 0.075 in.wc (18.6 Pa), then multiply flow by 1.89 for 50 Pa flow.
Max pressure = 0.050 in.wc (12.4 Pa), then multiply flow by 2.46 for 50 Pa flow.
Max pressure = 0.025 in.wc (6.2 Pa), then multiply flow by 3.86 for 50 Pa flow.

For example, if you get 6000 cfm at 0.1 in.wc (24.9 Pa),
then the approximate flow at 0.2 in.wc (50 Pa) would be
6000 times 1.57 =9420 cfm. These calculations assume a
the building flow formula is P^N where P is the
building pressure and N is the flow exponent of 0.65.

For further assistance, call (540) 943-2776 weekdays 7AM-4PM ET.