28
Table K: Venting Category Requirements
Support of Vent Stack
The weight of the vent stack or chimney must not rest
on the heater vent connection. Support must be pro-
vided in compliance with applicable codes. The vent
should also be installed to maintain proper clearances
from combustible materials. Use insulated vent pipe
spacers where the vent passes through combustible
roofs and walls.
Vent Terminal Location
1. Condensate can freeze on the vent cap. Frozen
condensate on the vent cap can result in a blocked
flue condition.
2. Give special attention to the location of the vent
termination to avoid possibility of property dam-
age or personal injury.
3. Gases may form a white vapor plume in winter.
The plume could obstruct a window view if the ter-
mination is installed near windows.
4. Prevailing winds, in combination with below-freez-
ing temperatures, can cause freezing of
condensate and water/ice build-up on buildings,
plants or roofs.
5. The bottom of the vent terminal and the air intake
shall be located at least 12 in. above grade, includ-
ing normal snow line.
NOTE:
During winter months check the vent cap
and make sure no blockage occurs from build-up of
snow or ice.
NOTE:
For additional information on appliance
categorization, see appropriate ANSI Z21 Standard
and the NFGC (U.S.), or B149 (Canada), or
applicable provisions of local building codes.
WARNING:
Contact the manufacturer of the vent
material if there is any question about the appliance
categorization and suitability of a vent material for
application on a Category I or III vent system. Using
improper venting materials can result in personal
injury, death or property damage.
CAUTION:
Condensate drains for the vent piping
are required for installations of the MVB. Follow vent
manufacturer instructions for installation and location
of condensate drains in the vent. Condensate drain
must be primed with water to prevent gas flue leak
and must be routed to an appropriate container for
neutralization before disposal, as required by local
codes.
NOTE:
Ensure that clearances are maintained per
Tables C and D.
CAUTION:
Vent piping is hot. Raypak recom-
mends the use of double wall or insulated wall pipe
to prevent personal injury.
Combustion
Air Supply
Exhaust
Configuration
Heater Venting
Category
Certified
Materials
Combustion Air
Inlet Material
From Inside Building
(Non-Direct Venting)
Vertical
Venting
I
B-Vent
Equivalent
Horizontal Through-
the-Wall Venting
III
Stainless Steel
From Outside Building
(Direct Venting)
Vertical
Venting
I
B-Vent
Equivalent
Galvanized Steel
PVC
ABS
CPVC
Horizontal Through-
the-Wall Venting
III
Stainless Steel
Extractors, Draft Inducers, and Motorized
Flue Dampers
When extractors or inducers are used in the venting
system, they must be interlocked with each connected
appliance, to ensure proper operation. If individual
motorized dampers are used, they must be interlocked
to their respective appliance. See Field Wiring
Connection section of this manual for proper wiring
instructions, using Fan/Damper dry contacts and
external interlock.
Summary of Contents for MVB 504A
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