Metal Fab Model M Installation And Maintenance Instructions

These symbols on the nameplate
means this product is listed by
Underwriters Laboratories Inc.
Listing No. MH7860

GENERAL:

The Model M Gas Vent has been designed for use with gas
burning Category 1 appliances. A Category 1 appliance
operates with a non-positive vent static pressure and with vent
temperature that avoids excessive condensate production in
the vent.
The vent is interconnected with a slip fit and maintained with
sheet metal screws. The vent is of a double-wall construction,
with the inner flue of aluminum alloy (allowing rapid warm-up
and better draft) and the outer casing of galvanized steel or
galvalume steel.

SAFETY:

CAUTION: UL approval is based on using B-Vent
components supplied by Metal-Fab, Inc. Performance may
be affected and a safety hazard created if parts shown in
these instructions are not used.
1. This gas vent must maintain one-inch
to combustibles for sizes 16-inch
inch . Two-inch
(610mm)
combustibles is required for sizes 26-inch
through 30-inch
(760mm)
other materials around the vent.
2. Use of draft increasers are limited to the exhaust end of
the vent system to maintain negative flue pressure.
3. Vent sizing is defined by tables in NFPA54 (ANSI Z223.1,
2002), or contact your Metal-Fab supplier. Install in
accordance with these instructions and local code
requirements.
4. Metal-Fab Type B Gas Vent and Fittings are to be used to
vent approved gas appliances intended to burn only gas.
Type B Vents are NOT to be used for the following:
A. Unlisted gas appliances
B. Incinerators
C. Recessed heaters
D. Conversion burners
E. Gas/oil burners
F. Any other appliance which may be readily converted
to a solid or liquid fuel.
G. Any other appliance not intended to burn only gas.
In areas where solid or liquid fuels are common, the
vent location should be marked "For use with vented
appliances burning only gas."
5. Locate vent as close as possible to the appliances to
obtain maximum draft and to minimize connector pipe
length.
6. Maintain a pitch or rise from appliance to vent on
horizontal runs. Minimum rise is ¼"
7. A vent cap should be used on all installations to prevent
back drafts and to keep out rain and debris.
clearance
(25.4mm)
through 24-
(406mm)
clearance to
(50.8mm)
(660mm)
. DO NOT pack insulation or
to the foot.
(6.4mm)
INSTALLATION AND MAINTENANCE
INSTRUCTIONS FOR LARGE DIAMETER
MODEL M GAS VENTS (B-VENT)
SIZES 16"
8. Venting into an unlined masonry chimney may cause
condensation. Install Type B Vent inside the chimney to
prevent condensation.
9. Do not install vent outside except where it is absolutely
necessary, and consult venting tables for proper design.
10. A gas vent support plate (MSP or MHS) is required if
vertical height exceeds 30'
between supports.
(9144mm)
11. When running vent through insulated areas, care must be
taken to prevent insulation from coming in contact with
the vent. This may be done by nailing headers between
joists through which vent is run, maintaining proper clearance
to combustibles or by nailing a firestop on top of joists to
prevent insulation from falling into boxed area.
12. Other than in single or two family dwellings, when gas
vent extends through ceilings above the room with
appliance(s), the vent is to be enclosed with materials
having a fire rating equal to or greater than floor, ceiling,
or roof.
13. It is not acceptable to penetrate the flue with screws
except when attaching drafthood to appliance outlet or
vent to single-wall connector.

INSTALLATION:

The Type B Gas Vent sections and associated components are
inserted one into another, then secured by sheet metal screws
(#8 x ½ ) provided with each section (See FIG. 1).
(13mm)
1. Starting at the appliance outlet or top of drafthood, attach
the first section or component. Secure with screws
provided.
NOTE: Some appliances have the draft hood built into the
appliance. For these, the gas vent attaches directly to the
appliance outlet (See FIG. 2). If needed, a draft hood connector
(MDC) is attached to the appliance outlet.
2. Continue upward with the gas vent. If a floor is to be
penetrated, an MSP support plate or firestop is required.
A field fabricated firestop is acceptable. To field fabricate
a firestop, use a 26-gauge galvanized steel plate. Cut a
hole slightly larger than the gas vent O.D. Position the
firestop to maintain correct clearance to combustibles, then
nail in place.
NOTE: A MSP is required for every 30 feet
stack to support the load.
3. When penetrating the roof, cut hole to maintain clearance
to combustibles. The MF flashing and MSC storm collar
are used to cover the hole in the roof. Terminate the vent
using the MC cap. If vent is more than 6 feet above where
it penetrates the roof, additional support is required.
(See FIG. 4.)
NOTE: For Canadian installations, use cUL section, designated
with a suffix G, on vent sections exposed to atmosphere.
THROUGH 30"
(406MM) (760MM)
. Maximum of 30'
(9144mm)
(9144mm)
of vent