MFC Series Boiler Vent and Combustion Air Guide
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GF-148-V
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3/29/2023
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The condensate trap assembly is located directly below the exhaust manifold. Plastic hose should
be connected to the trap assembly and run to drain. Care should be taken to avoid hose kinks
and to avoid raising the hose above the trap assembly. Condensate should flow freely to drain.
The condensate-to-drain run must not be hard-piped so the trap can be removed periodically for
maintenance purposes.
If the condensate must be lifted above the trap assembly to a drain, it should be drained into a
sump. From there, a pump can lift the condensate away.
Each unit will produce the following approximate condensate quantities in the full condensing
mode:
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MFC 3000 = 20 gallons per hour
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MFC 4000 = 27 gallons per hour
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MFC 5000 = 34 gallons per hour
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MFC 6000 = 40 gallons per hour
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MFC 8000 = 54 gallons per hour
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MFC 10000 = 68 gallons per hour
Condensate drain systems must be sized for full condensing mode.
In multiple boiler applications, it is common to manifold these drains together in a plastic pipe
manifold to a floor drain. Condensate manifolds must be large enough to handle the anticipated
flow and must be properly secured and protected. Manifolds are generally located behind the
boilers so that short runs of plastic tubing into the manifold can be used for the condensate drain.
A base drain must be installed at the bottom of vertical common flue piping.
The pH level of the condensate, produced by MFC Series boilers, ranges between 3.0 and 3.2.
The installation should be designed in accordance with local codes that specify acceptable pH
limits. If required, any type of commercially available neutralizer may be used.
16.
Individually Vented Systems
Systems with individual vents may be used with any of the combustion air systems described
previously and illustrated in Section 4. The maximum combined pressure drop of the vent and
combustion air system must not exceed 140 equivalent feet of length.
To calculate the pressure drop:
1) Calculate the exhaust vent pressure drop.
2) Calculate the combustion duct pressure drop.
3) Divide the vent pressure drop by the altitude correction factor (CF) listed in Table 7 to
correct for installations above sea level.
4) Determine the natural draft, if any, from Table 6 and multiply it by the altitude CF.
5) Add
the altitude corrected vent pressure drop (positive) and the draft (negative) to get the
total vent pressure drop.
6) Add the total vent pressure drop to the altitude corrected combustion air duct pressure
drop.
The total system pressure drop must not exceed 140 equivalent feet.
16.1 MFC Series Pressure Drop Calculation Example
Calculate the maximum pressure drop for a single boiler installation at 500 feet above sea level
having a winter design temperature of 20°F. The duct system of an MFC 3000 consists of:
1) An 10-inch diameter exhaust vent with two (2) 90° elbows, one (1) 45° elbows, 75 feet of
