speed. Do not operate summer exhaust fan. Close
replace dampers.
4. Place in operation the appliances being inspected.
Follow the manufacturer’s instructions for lighting
each appliance. Adjust thermostat so appliance
will operate continuously.
5. Check the pressure at a pressure tap located 12
in. above the bottom joint of the rst vertical vent
pipe. Pressure should be anywhere between -0.01
and -0.08 in. WC.
6. After it has been determined that each appliance
remaining connected to the common venting sys-
tem properly vents when tested as outlined above,
return doors, windows, exhaust fans, replace
dampers and other gas burning appliances to their
previous conditions of use.
7. Any improper operation of the common venting
system should be corrected so that the installation
conforms with the NFGC (U.S.) or B149 (Canada).
When re-sizing any portion of the common venting
system, the common venting system should be
re-sized to approach the minimum size as deter-
mined using the appropriate tables in the NFGC
(U.S.) or B149 (Canada).
*
CAT III CERTIFIED
INSULATED
EXHAUST VENTING
Fig. 26: Horizontal Through-the-Wall Venting (Category III)
*Requires optional vent tee.
The total length of the horizontal through-the-wall ue
system should not exceed 70 equivalent ft in length.
If horizontal run exceeds 70 equivalent ft, an appro-
pri-ately sized extractor must be used. Each elbow
used is equal to 10 ft of straight pipe. This will allow
installa-tion in one of the four following arrangements:
• 70’ of straight ue pipe
• 60’ of straight ue pipe and one elbow
• 50’ of straight ue pipe and two elbows
• 40’ of straight pipe and three elbows
The vent cap is not considered in the overall length of
the venting system.
The vent must be installed to prevent ue gas leakage.
Horizontal Through-the-Wall Venting
(Category III)
Installation
These installations utilize the heater-mounted blow-
er to vent the combustion products to the outdoors.
Combustion air is taken from inside the room and the
vent is installed horizontally through the wall to the out-
doors. Adequate combustion and ventilation air must
be supplied to the equipment room in accordance with
the NFGC (U.S.) or B149 (Canada).
30
APPROVED
UNCONTROLLED DOCUMENT IF PRINTED
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