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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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Mon-Fri, 8 am - 5 pm EST Page 9 of
33
4.4 One Permanent Opening Method
One permanent opening shall be provided, commencing within 12 inches (300 mm) of the top of
the enclosure. The appliance shall have clearances of at least 1 inches (25 mm) from the sides
and back of the appliance, and a clearance of 6 inches (150 mm) from the front. The opening
shall communicate with the outdoors directly or through a vertical or horizontal duct to the
outdoors or spaces that freely communicate with the outdoors (as shown in Figure 6) and shall
have a minimum free area as follows:
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1 inch
2
per 3,000 BTU/hr (700 mm
2
/kW) of the total input rating of all appliances located
in the space.
Figure 6: All Combustion Air from Outdoors through Single Combustion Air
Opening
4.5 Opening a Louver Through the MFC Series Boiler
A louver can be opened using the auxiliary relay contacts, part of the MFC burner controls. These
contacts are provided by a single pole double throw (SPDT) relay that is energized when there is
a demand for heat and is de-energized after that demand is satisfied. The relay contacts are rated
for 120 VAC at 5 amps, resistive.
NOTE:
Do NOT power the louver directly using the Auxiliary Relay. An external relay (supplied by
others) must be employed for this purpose. The boiler power cannot support external
accessories.