Daikin DM80SE, Service Instructions Manual

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28
SERVICING
CHECKING GAS VALVE (Redundant)
A combination redundant operator type gas valve which
provides all manual and automatic control functions required
for gas fired heating equipment is used.
The valve provides control of main burner gas flow, pressure
regulation, and 100 percent safety shut-off.
WARNING
D
ISCONNECT
ALL
POWER BEFORE SERVICING
Single stage gas valves should be tested on the furnance
with 24 VAC connected to the gas valve and manometers
reading supply line and manifold pressures.
WARNING
D
ISCONNECT
ALL G
AS AND
E
LECTRICAL
P
OWER
S
UPPLY.
Orifices should be treated with care in order to prevent
damage. 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. This will
change the angle or deflection of the vacuum effect or
entraining of primary air, which will make it difficult to adjust
the flame properly. This same problem can occur if an orifice
spud of a different length is substituted.
WARNING
D
ISCONNECT
ALL G
AS AND
E
LECTRICAL
P
OWER
S
UPPLY.
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.
CAUTION
Gas inlet and manifold pressures should be checked and
adjusted in accordance 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
measured 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.
WARNING
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
compartment 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 pressure
tap or the gas piping drip leg as shown in the following
figures. Refer to Measuring Gas Pressure: Single Stage
Valves figure for single stage valve inlet pressure tap
connections.
NOTE: At either location, a hose fitting must be installed prior
to making the hose connection.
NOTE: Use apapter kit #0151K00000S to measure gas
pressure on White-Rodgers 36J22 gas valves.
Mode
10.0
Measuring Inlet Gas Pressure
(Alternate Method)
3. Turn ON the gas and electrical power supply and operate
the furnace and all other gas consuming appliances on
the same gas supply line.
4. Measure furnace gas supply pressure with burners firing.
Supply pressure must be within the range specified in the
following table.
INLET GAS SUPPLY PRESSURE
Natural Gas Minimum: 4.5" w.c. Maximum: 10.0" w.c.
If supply pressure differs from above, make necessary
adjustments to pressure regulator, gas piping size, etc., and/
or consult with local gas utility.