Types Of Gas Venting Systems - Weil-McLain 4 Series Manual

sTeam series
94

Types of Gas Venting Systems

Category III venting: positive pressure and not
likely to condense in the vent .
Boiler, breeching and vent operate at positive
pressure The entire engineered vent system must
be rated for Category III venting Ensure 0 1" positive
pressure at test opening The minimum vent height is
3 feet above roof or snow line, and in accordance to
local codes that have jurisdiction See Figure 35
Category I venting: negative pressure and not
likely to condense in the vent .
Boiler operates with positive pressure overfire.
Chimney may provide excess draft, which may
require the installation of a draft control device to
minimize draft in accordance to local codes that have
jurisdiction The control must be set to maintain 0 1"
positive pressure at the flue collar. The minimum
vent height is 3 feet above roof or snow line, and in
accordance to local codes that have jurisdiction See
Figure 36 and Figure 37
Figure 36 Category I venting, single boiler (typical shown)
230045
550-100-157/0523
boiler manual
4
Figure 35 Category III venting, single boiler (typical shown)
230044
Figure 37 Category I venting, multiple boilers (typical
shown)
insTallaTion
15 feet
typical
230046
45
1
2
3
4
5
6
7
8