MFC Series Boiler Vent and Combustion Air Guide
TAG-0080_OG
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GF-148-V
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3/29/2023
Technical Support
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(800) 526-0288
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If the vent system is to be connected to an existing stack, the stack must be UL listed for Category
II and IV appliances (capable of 350
F, positive pressure and condensing flue gas operation).
Masonry stacks must be lined, and the vent penetration must terminate flush with, and be sealed
to, this liner. Vents may enter the stack through the bottom or side. All side connections must
enter at a 45-degree connection in the direction of flow and must enter at different elevations, with
the smallest vent connection at the highest elevation. MFC vents must not be connected to other
manufacture
r’s equipment.
The exhaust vent must be pitched upward toward the termination by a minimum of ¼ inch per
foot of length. Condensate must flow back to the MFC unit freely, without accumulating in the
vent.
4.
Combustion Air Supply
The MFC boilers require the following combustion air volumes when operated at full capacity.
TABLE 2: Required Combustion Air
Volumes (at Full Capacity)
UNIT
VOLUME
MFC 3000
700 SCFM
MFC 4000
935 SCFM
MFC 5000
1170 SCFM
MFC 6000
1400 SCFM
MFC 8000
1870 SCFM
MFC 10000
2335 SCFM
These flows MUST be accommodated. Air supply is a direct requirement of NFPA, CSA B149.1-
10 (Canada) and local codes that should be consulted for correct design implementation.
In equipment rooms containing other air-
consuming equipment ― including air compressors and
other combustion equipment ― the combustion air supply system must be designed to
accommodate all such equipment when all are operating simultaneously at maximum capacity.
Combustion air intakes must be located in areas that will not induce excessive (>0.10" water
column (W.C.)) intake air pressure fluctuations. Designs should take into account equipment
blowers and exhausts when using room air for combustion.
Intakes should be located to prevent infiltration of chlorides, halogens or any other chemicals that
would be detrimental to the operation of combustion equipment. Common sources of these
compounds are swimming pools, degreasing compounds, salts, plastic processing and
refrigerants. When the environment contains these types of chemicals, the air MUST
be supplied
from the outdoors using direct-vent/ducted-combustion ductwork.
Air intakes must not be located in the proximity of garages, industrial and medical hood venting,
loading docks or refrigerant vent lines. Boilers should not be installed in the proximity of activities
that generate dust if that dust can enter the boiler intake. Boilers should be located to prevent
moisture and precipitation from entering combustion air inlets.
When a boiler is used, temporarily, to provide heat during ongoing building construction or
renovation, accumulated drywall dust, sawdust and similar particles can:
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Accumulate in the unit’s combustion air intake and block combustion air flow.
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Accumulate over the burner surface and restrict flow of air/fuel mixture.
