Checking Main Burners; Servicing; Checking Orifices; Checking Gas Pressure - Goodman GMVM Service Instructions Manual

SERVICING

S-305

CHECKING MAIN BURNERS

The main burners are used to provide complete combustion
of various fuels in a limited space, and transfer this heat of
the burning process to the heat exchanger.
Proper ignition, combustion, and extinction are primarily due
to burner design, orifice sizing, gas pressure, primary and
secondary air, vent and proper seating of burners.
Depending on the size of the furnace, each furnace will
havefrom three to five inshot burners. Burners are precisely
constructed of aluminized steel and designed to provide
proper ignition and flame stability. When converting a modu-
lating furnace to L.P. gas, the factory installed burners must
be replaced by burners that come in the L.P. kit.
D A L L G
IS C ON N E CT A S A N D
In checking main burners, look for signs of rust, oversized
and undersized carry over ports restricted with foreign ma-
terial, etc, refer to Beckett Burner drawing.
Beckett Burner
S-306

CHECKING ORIFICES

A fixed gas orifice is used in all Goodman
brand furnaces. That is an orifice which has a fixed bore
and position as shown in the following drawing.
No resizing should be attempted until all factors are taken
into consideration such as inlet and manifold gas pressure,
alignment, and positioning, specific gravity and BTU con-
tent of the gas being consumed.
Orifices should be treated with care in order to prevent dam-
age. They should be removed and installed with a box-end
wrench in order to prevent distortion. In no instance should
an orifice be peened over and redrilled.
WARNING
E P S
LE C TRIC A L O W E R U PP LY.
®
brand & Amana
The length of Dimension "A" determines the angle of Gas
Stream "B".
A dent or burr will cause a severe deflection of the gas stream.
S-307 CHECKING GAS PRESSURE
Gas Supply Pressure Measurement
T
O PREVENT UNRELIABLE OPERATION OR EQUIPMENT DAMAGE, THE
INLET GAS SUPPLY PRESSURE MUST BE AS SPECIFIED ON THE UNIT
RATING PLATE WITH ALL OTHER HOUSEHOLD GAS FIRED APPLIANCES
OPERATING.
Gas inlet and manifold pressures should be checked in ac-
cordance to the type of fuel being consumed.
The line pressure supplied to the gas valve must be within
the range specified below. The supply pressure can be mea-
sured at the gas valve inlet pressure tap or at a hose fitting
installed in the gas piping drip leg. The supply pressure must
®
be measured with the burners operating. To measure the
gas supply pressure, use the following procedure.
D
ISCONNECT ELECTRICAL POWER AND SHUT OFF GAS SUPPLY.
1. After turning off gas to furnace at the manual gas shutoff
valve external to the furnace, remove burner compart-
ment door to gain access to the gas valve.
2. Connect a calibrated water manometer (or appropriate
gas pressure gauge) at either the gas valve inlet pres-
sure tap or the gas piping drip leg as shown in the follow-
ing figures.
A
GAS
STREAM B
DENT OR
BURR
GAS
STREAM B
CAUTION
WARNING
71