Owner's Manual

Rev. 03-03-2016 Copyright (C) 2016, Heat Outdoor Living Page 9
increased static pressure and decrease performance.
IMPORTANT: Even though the intake side of the roof cap or wall cap may be properly sized, roof caps or wall caps need to have the
actual open area of the final air path that is equal to or greater than the discharge port of the hood. Any undersized portion of a roof
cap or wall cap will cause excessive static pressure that may result in rattling, vibration and air buffeting noises, as well as inadequate
ventilation.
Do Not use “goose-neck style” caps as they significantly restrict natural, heated air-flow. Do Not use caps with dampers for BBQ
Hoods.
Fig. 1 Fig. 2
The air exit opening on the roof cap used needs to be at or above 78.5 square inches. See illustrations above. Never use a roof cap like
the one shown in Figure 1. Instead use a style similar to the one shown in Figure 2.
7. Attaching Duct to House Framework
The ventilation system should be attached to the framework in such a manner that the weight of the duct and fittings is supported
with no stress on the duct joints, fittings or on the ventilator. All ducting should be attached so as to avoid any possible duct vibration
from being transferred to the house’s framework.
8. Duct Sizing Chart and Area Calculations
Ventilator Discharge Port
Types & Sizes
Duct Type Required
Minimum Duct Size
(in Square Inches)
Minimum Discharge Size of Roofcap
or Wallcap Outside Opening
10” Diameter, Round
(Area is 78.5 Square Inches)
10” Round Metal Duct or
78.5”
78.5”
8” x 10” Rectangular Duct
80”
80”
Formulas for Calculating Square Inches of Various Duct Sizes & Types
ROUND DUCT
RECTANGULAR DUCT
Radius
x
Radius
x
3.1416
=
Area (Sq. Inches)
Width
x
Depth
=
Area (Sq. Inches)
x
x
=
x
=
The “radius” is one-half the diameter of a round duct, e.g., ½ of a
10” round duct is 5”. 3.1416 is “Pi”, the “constant” used when
calculating the area of a circle.