36
Installation Manual
Common Vent System Information (Optional)
About the Common Vent System
Common Vent System allows multiple VST water heaters to share
the same vent system, which means fewer wall or roof cuts, less
labor, and longer vent lengths than with single-unit water heater
venting.
• VRP - 199
• VRS – 199
Danger
• Category IV appliances require a special venting system. The
vent system will operate with a positive pressure in the pipe.
• Exhaust gases must be piped directly outdoors using the
vent materials and rules outlined in these instructions. Do
not connect vent connectors serving appliances vented
by natural draft into any portion of mechanical draft
systems operating under positive pressure. Follow the
venting instructions carefully. Failure to do so will result
in substantial property damage, severe personal injury or
death.
Warning
• Improper venting of the water heater units can result in
excessive levels of carbon monoxide, which can lead to
severe personal injury or death. The water heaters units
must be vented in accordance be vented in accordance with
the "Venting of Equipment" section of the latest edition of
the ANSI Z223.1/NFPA 54 Natural Fuel Gas Code in the USA,
as well as all applicable local building codes and regulations.
Follow all instructions and guidelines when venting the
water heater units.
Venting should be performed only by a licensed
professional.
• Venting system must be sealed gastight to prevent flue gas
spillage and carbon monoxide emissions, which will result in
severe personal injury or death.
• The building owner is responsible for keeping the exhaust
and intake terminations free of snow, ice, or other potential
blockages, as well as scheduling routing maintenance.
Blocked or obstructed vent piping terminations could result
in property damage, severe personal injury, or death.
Guideline for a Common Vent
System
Caution
• To ensure the correct operation of the common vent system,
- A cascade communication cable must be installed
between all units in the common vent system by the
installer.
- Backflow dampers must be installed in the exhaust duct of
each water heater unit.
• This manual covers the installaion of a common vent system
for VR water heaters only.
To ensure the safe and correct installation of the common vent
system, carefully follow the instructions and guidelines.
• A maximum of 8 VR water heaters may be connected to one
common vent system. In a system that has more than 8 VR water
heaters, use 2 common vent systems or consult VST.
• Position the water heaters units as close as possible to the vent
termination.
• Do not use cellular core PVC (ASTM F891),cellular core CPVC,
Radel® (polyphenolsulfone), ABS, or galvanized material for the
exhaust vent.
• Support horizontal vent runs a minimum of every four feet and
all vertical vent runs a minimum of every six feet..
• Venting should be as direct as possible with a minimum number
of pipe fittings.
• Vent connections must be attached together so that they form
an air tight seal.
• If the water heater units will be installed in areas where snow
is known to accumulate, protect the vent termination from
blockage. Provide a minimum of 1 foot (30 cm) clearance from
the bottom of the exhaust of the expected snow accumulation
level. Snow removal may be necessary to maintain clearance.
• Set the temperature setting on all water heaters being common
vented to the same temperature.
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