Thermador RDDS30V, Installation Instructions Manual

Page: 15 / 20

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A. Duct Fitting Equivalent
Quantity Fitting Equivalent
Description Length
1 6" Dia to 3-1/4" x 10" 1 Ft.
2 3-1/4" x 10" 90
°
elbows
(2 @ 10 feet) 20 Ft.
1 3-1/4 x 10" Wall cap
(Model# 12551)
2 Ft.
Total "A" Duct Fitting Equipment 23 Ft.
B. Straight Duct Length
1 15 Ft.of 3-1/4 x 10"
rectangular duct
15 Ft.
1 1 Ft. of 3-1/4" x 10"
rectangular duct
1 Ft.
1 6 Ft. of 3-1/4 x 10"
rectangular duct
6 Ft.
Total "B" Straight Duct Length 22 Ft.
C. Total Equivalent Straight =23+22=45 Ft.
Once you've determined the value of C, refer to Chart 1
for internal blower (Page 16) to find the minimum C.F.M.
for 3-1/4" x 10" rectangular duct. Note that the chart
legend furnishes different lines for different ducting sizes
and shapes. By using the correct line, you can see that 45
feet of rectangular duct equates to approximately 420
C.F.M.
BLOWER DUCT SIZING
Based on the blower position, determine the
required straight duct length and size, and the
number and types of elbows or transitions.
Calculate the total equivalent length using this
equation: A+B = C
A = Duct fitting equivalent straight length (use Table 1,
Page 17).
B = Straight duct length of smallest duct used.
C = Total equivalent straight length of the smallest size
ducting used.
Use the value of C from Chart 1, Page 16 (Internal
Blower) or Chart 2 (Remote Blower) to determine the
C.F.M.
NOTE: We recommend a minimum of 350 cubic
feet per minute (C.F.M.) Flow for the range
downdraft system.
FOR EXAMPLE: An internal ventilation system, using
model VTN30RQ, would have a total equivalent length of
45 feet when using fittings noted on Page 17.
Figure 23B - Top View of 3-1/4" x 10" Adapter
in two positions
➛
Model # RD310
3-3/8"
➛
10-3/4"
➛
➛
CALCULATING CUBIC FEET PER MINUTE (C.F.M.)
Gasket
Plenum
Adapter
Studs Located on Bottom of
Exhaust Plenum
➝
Adapter Mounting
Bracket
Figure 24
CL