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The stainless steel direct vent cap must be furnished
by the boiler manufacturer in accordance with its list-
ing (sales order option D-15).
Use only double-wall vent pipe and the special gas
vent pipes listed for use with category II or IV gas burn-
ing boilers, such as the stainless steel Saf-T vent by
Heat Fab Inc. (800-772-0739), Protech Systems Inc.
(800-766-3473), or Z-Flex (800-654-5600). Pipe joints
must be positively sealed. Follow the vent manufactur-
er’s installation instructions carefully.
Direct Vent - Horizontal Through-
the-Wall
Installation
These installations utilize the boiler-mounted blower to
draw combustion air from outdoors and vent combus-
tion products to the outdoors.
The total length of the direct vent through-the-wall
exhaust vent cannot exceed 40 ft in length for the flue
outlet. Each elbow used is equal to 10 ft of straight
pipe. This will allow installation in one of the three fol-
lowing combinations:
• 40’ of straight flue pipe
• 30’ of straight flue pipe and one elbow
• 20’ of straight flue pipe and two elbows
The total length air supply duct cannot exceed the dis-
tances listed. Each elbow used is equal to 10 ft of
straight pipe. This will allow installation in one of the
three following combinations:
• 40’ of straight combustion air pipe
• 30’ of straight combustion air pipe and one elbow
• 20’ of straight combustion air pipe and two elbows
The flue exhaust direct vent cap is not considered in
the overall length of the venting system.
Care must be taken during assembly that all joints are
sealed properly and are airtight.
The vent must be installed to prevent the potential ac-
cumulation of condensate in the vent pipes. It is rec-
ommended that:
1. The vent must be installed with a slight downward
slope of not more than 1/4 inch per foot of hori-
zontal run to the vent terminal.
2. The vent must be insulated through the length of
the horizontal run.
For installations in extremely cold climate, it is rec-
ommended that:
1. The vent must be installed with a slight upward
slope of not more than 1/4 inch per foot of hori-
zontal run to the vent terminal. In this case, an ap-
proved condensate trap must be installed per ap-
plicable codes.
2. The intake vent must be insulated through the
length of the horizontal run.
Common Venting System
Common venting of Category IV systems is not al-
lowed.
The stainless steel flue exhaust direct vent cap must
be furnished by the boiler manufacturer in accordance
with its listing (sales order option D-15).
Use only double-wall vent pipe and the special gas
vent pipes listed for use with category II or IV gas burn-
ing boilers, such as the stainless steel Saf-T vent by
Heat Fab Inc. (800-772-0739), Protech Systems Inc.
(800-766-3473), or Z-Flex (800-654-5600). Pipe joints
must be positively sealed. Follow the vent manufactur-
er’s installation instructions carefully.
Fig. 42: Direct Vent - Horizontal Through-the-Wall
WARNING: No substitutions of flue pipe or vent
cap material are allowed. Such substitutions would
jeopardize the safety and health of inhabitants.