c. Calculate the percent area for each
individual surface thermocouple based on the total
calculated wetted surface area of all 20
pre-determined thermocouple locations.
d. Identify the thermocouple temperatures that
are less than the dew point temperature of the
standard dew point temperature of 5.0 C (41 F) (if
that is the dew point temperature assigned as the
standard).
e. Calculate the percentage of area that has
surface temperatures less than the dew point
temperature and subtract that from the total
percentage of area (100%).
f. That number would reflect the amount of
interior window area that would exhibit condensation
at the prescribed conditions. This number would be
the Condensation Index (CI).
For products that cannot be simulated, the following
procedures shall be used to determine the
Condensation Index:
Use the current wiring diagrams and temperature
measurement locations as specified in the NFRC Test
Procedure. These are pre-specified locations for
temperature measurement on the interior surfaces of
the glass and frame members. The surface
temperatures shall be area-weighted in the same
manner as for U-factor calculation purposes. The
window product should not have a Condensation Index
less than 85, meaning that 14% or less of the
product will exhibit condensation on the interior
area-wetted exposed surfaces. Of the 14% area
permitted to exhibit condensation, no greater than
5% of the interior surfaces of the frame members
shall have condensation in any form. The window
product Condensation Index must meet the criteria
prescribed in the following table:
Minimum Recommended Condensation Index Ratings
Relative
20%
25%
30%
35%
40%
45%
50%
Humidity
Dew Point -3.3C 0.6C 2.8C 5.0C 7.2C 9.4C 10.0C
@ 21.1 C (26F) (33F) (37F) (41F) (45F) (49F) (50F)
(70.0 F)
Outside Design Temperature
-34
C
(-30 F)
85
85
85
85
90
95
95
-29
C
(-20 F)
85
85
85
85
90
95
95
-23
C
(-10 F)
85
85
85
85
85
90
95
-18
C
(0 F)
85
85
85
85
85
90
95
-12
C
(+10 F)
85
85
85
85
85
90
95
SECTION 08520A
Page 9
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