Goodman GMVM Service Instructions Manual page 15

PRODUCT DESIGN
Furnace Components
Heat Exchanger Assembly
The primary heat exchanger is a tubular type constructed of
high quality steel (stainless steel for Amana Brand, alumi-
nized for Goodman) the heat exchanger assembly consists
of primary and secondary sections crimped together on a
back transition plate. The secondary heat exchanger is a
single pass coil consisting of stainless steel tubes and alu-
minum fins. These stainless steel tubes are expanded on to
the aluminum fins to enhance heat transfer. Each tube in the
secondary heat exchanger contains an internal turbulator to
effectively scrub heat from the flue gases. Flue gas conden-
sation takes place in the secondary heat exchanger as la-
tent heat is transferred from the flue gases to heat the condi-
tioned space.
Burners
Depending on the size of the furnace, each furnace will have
from three to five inshot burners. Burners are precisely con-
structed of aluminized steel and designed to provide proper
ignition and flame stability. When converting the modulating
furnace to L.P. gas, the factory installed burners must be
replaced by burners that come in the L.P. kit.
Gas Manifold Assembly
Each gas manifold is fitted with the appropriate number of
#45 natural gas orifices. At 100% of gas input, each burner
will provide approximately 20,000 BTUH. The A/
GMVM951155DX models uses #43 gas orifices at 22,500
per hour. If converting to LP gas, the factory installed mani-
fold assembly must be replaced by the manifold assembly
provided in the LP kit.
ECM Motor
An Emerson® UltraTech® four wire indoor fan motor provides
supply air to the conditioned space. This is the same motor
used on Goodman & Amana previous generation communi-
cating furnaces.
Induced Draft Blower (IDB)
All modulating furnace models use a three phase induced
draft blower to draw flue gases through the heat exchanger.
The inducer uses ball bearings and is permanently lubricated.
This motor is driven at varying speeds by the VFD (variable
frequency drive) section of the IFC. The IFC takes typical
single phase power supplied to the furnace and converts it to
a three phase supply to operate the draft inducer at the de-
sired speed. The windings of the induced draft motor will have
equal resistance +/- 5%. Normal resistance readings at room
temperature will range from 14-17 ohms. The voltage sup-
plied by the IFC to drive the induced draft blower will vary
from 15-110 volts A/C between any two windings. This would
be read between any two of the three power wires between
the IFC and the induced draft blower. This voltage to the IBD
will vary between furnace models and is dependant on what
percentage of maximum fire is being called for. The power
wires are colored red, white, and black. A green colored ground
wire is also present.
Hot Surface Igniter
Modulating furnaces use a 115 volt silicon nitride hot surface
igniter. This is the familiar and reliable 0131F00008S igniter
with 17 second warm up time. At room temperature the ig-
niter has a resistance range of 37 - 68 ohms. The H.S.I. is
connected electrically to the IFC by a 3/16" push-on connec-
tion.
Gas Valve
Modulating furnaces use a 24 VAC pneumatically operated
gas valve by Honeywell. The valve is energized by the inte-
grated furnace control on a call for heat, wired in series through
the front-cover pressure switch. The firing rate percentage is
determined by the negative pressure created by the opera-
tion of the draft inducer. The gas valve is factory set and non-
adjustable in the field. Do not remove the seal covering the
regulator screws or attempt to adjust either of the regulator
screws.
Inductor Coil
Wired in series with ¾ and 1 HP ECM motors; the inductor
coil conditions the power supply to the motor, smoothing out
spikes and electrical noise. With voltage applied to one side
of the inductor coil, the output voltage to the motor should be
the same as incoming voltage.
Integrated Furnace Control (IFC)
The IFC is the main control center for the furnace. It has
many functions including;
• Receiving commands from the thermostat for heating,
and cooling, continuous fan operation.
• Receiving commands for dehumidification and humidi-
fication.
• Communicating with the ECM motor for proper air de-
livery to the conditioned space.
• Assuring safe ignition by checking the state of pres-
sure switches and limit switches before and after igni-
tion.
• Assuring safe operation by continuously monitoring the
presence of flame, the state of the pressure switches
and limit and roll out switches.
• Displays information on the dual seven segment dis-
plays regarding thermostat call, air flow delivery and
fault status
• Controlling the speed of the induced draft blower by
variable voltage & frequency.
Features of the IFC:
Aux Terminals Located next to the low voltage connector,
there are two terminals labeled aux in & aux out. A factory
jumper is installed between these two terminals. As an op-
tion; the jumper may be removed and the terminals wired up
to a normally closed float switch. The switch must be closed
for normal operation. If the switch is sensed open, the IFC
will:
• Terminate a call for gas heat.
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