MGD Gas Furnace
Service Manual
Fundamentals of the Gas Furnace
All gas furnaces consist of four main components: a burner, a heat exchanger, a blower and a
vent pipe or flue.
The burner is where the gas is delivered and burned. The gas furnace uses an electronic ignition
system and hot surface igniter instead of a constantly burning pilot light to ignite the gas.
Whenever the thermostat calls for heat, the ignition device instantly lights the burners. The hot
surface igniter is only energized when the thermostat first calls for heat and is de-energized after
ignition. By not using any gas between ignition cycles, these components conserve the fuel
previously used by a standing pilot light while providing added safety as well.
The heat exchanger transfers the heat produced from the burning gas to the home's conditioned
air distribution system and is engineered to provide maximum heat transfer to the conditioned air.
The circulation blower moves the conditioned air through ducts to the location in the home where
it is needed. This is a squirrel cage type blower powered by an electric motor, both of which have
been sized for their specific application.
The flue exhausts the gaseous byproducts of combustion to the outdoors. Venting is also
provided through the chimney. The MGD furnaces use sealed combustion systems tested and
listed for use
only
with
RJ – Series Roof Jack Venting System
.
The MGD furnaces are set up to burn natural gas and can be converted to burn LP or propane.
ELECTRICAL SUPPLY
The unit cannot be expected to operate correctly unless it is properly connected (wired) to an
adequately sized single branch circuit. Check the Technical Data Section of this manual to
determine if the circuit is adequately sized.
WARNING
Electrical Shock hazard
Turn OFF electric power at fuse box or service panel before making any electrical
connections and ensure a proper ground connection is made before connecting
line voltage.
Failure to do so can result in property damage, personal injury and/or death.
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