Optal 4 Glass 2 burners, Installation & Operation Manual

Page: 61 / 166

61
Vertical Elbows
The example that follow reference the table for the burner 30/ Series 40 models on page 63 for
scenarios A, B, C and D on page 62.
A. When you have vertical elbows of 45 degrees, no additional length for the (H) calculation
for the restrictor plate size is needed.
Example: Total height of duct work = 6 feet (V)
Length between the center of the two 45-degree elbow = (B) = 3ft.
The (H) calculation is (H) = (B) so the restrictor plate size is 1.97” per the table.
B. If there are two 90-degree elbows in the vent system, an additional 6 feet must be added
to the (H) calculation for the restrictor plate size.
Example: Total height of duct work = 18 feet (V)
Length between the center of two 90-degree elbows = (B) = 21 feet.
The (H) calculation to be used in the restrictor table is (H) = (B) +6 feet, therefore (H) length is 27
feet.
Per the table the restrictor plate is 0. No restrictor is required.
C. The first 90-degree elbow is not taken into calculation of the (H) length for the restrictor
plate size.
Example: Total height of duct work = 15 feet (V)
Length between the center of 90-degree elbow and wall termination cap = (B) = 11ft.
The (H) calculation is (H) = (B) = 11, therefore restrictor plate size is 1.18” per the table.
“11” does not appear on the x scale of the table. The choices are then 9 and 12. Always choose the
next higher value, which is also the smaller restrictor if there is a difference between the values
provided.
D.
There are no 90-degree elbows or 45 degree angles. The venting is a straight vertical run.
Example: Total height of duct work = 24 feet (V)
The (H) calculation is = 0. Therefore, restrictor plate size is 1.97”.
NOTE:
1. Only two 90-degree elbows are allowed per installation. More than two 90-degree
elbows require manufacturer’s approval.
2. Each 90 degree bend can be calculated as 2 x 45 degree bends.
- For example, a given installation can have:

2 x 45 degree bends and one 90, or

4 x 45 degree bends and no 90