Specifications

22
5.1 Design Guidelines for Mechanical Venting of
Gas and Manually Fired Appliances
There are two ways to determine the chimney fan
type and size for the specic application.
One alternative is to calculate the ue gas volume
and the ow resistance and then select the chimney
fan that meets the calculated requirements. This is
normally referred to as an “approved engineered
method”. For directions on how to do a manual
calculation please refer to Appendix A.
Please note that the size and selection charts are
based on elevation of up to 2,000 feet above sea
level. For elevations greater than this please contact
your supplier or call ENERVEX 800.255.2923 for
assistance.
The sizings and the selection charts in the following
are based on these assumptions:
5.1.1 Fireplaces – wood or gas
Most applications are relatively simple, and following
these four steps makes it easy to size a proper
chimney fan for an application.
Use the following charts to determine the opening of
the appliance:
5. Mechanical System Design
Fireplace
Type
Formula to determine opening size
One-sided A x H
Two-sided
(See-through)
2 x A x H
Corner (A x B) x H
Three-sided (A+B+C) x H
Free-standing (A+B) x H x 2
Free-standing
round
A x H x 3.14
Height of chimney: 18-25 feet
Flue gas temperature:
Wood 300°F
Gas 200°F
Frontal inlet velocity:
Fireplace (wood-red) 48 fpm
Fireplace (gas-red) 36 fpm
Stoves (wood-red) 84 fpm
Step 1 - Determine the size of the appliance opening
A
H
H
A
H
BA
A
H
C
B
H
B
A
H
A