Specifications

IM 685-2 9
5. Check voltage. With burner switch S3 at AUTO, measure
voltage across burner control box terminals 2 and NB. If
it is not between 114 and 126 volts, check the voltage and
tapping connections to the supplying transformer at the
unit main control panel.
6. Purge the gas lines. Turn off electrical power. Remove
the 1/8 inch pipe plug from the inlet pressure tap of the
first electric gas valve in the line, open the gas line cocks
upstream from there and bleed the gas line of all air.
Replace the 1/8 inch pipe plug.
7. Leak check. Using a rich soap-water mixture and a brush,
check the gas lines for leaks. Correct all leaks before
starting burner. After the burner is operating and all the
downstream valves are open, leak check that portion of
the gas train.
8. Connect a manometer to measure gas manifold pressure.
There is a 1/8 inch pipe size plugged tapping in the gas
line just before it enters the burner housing.
Preliminary “Dry” Run
1. Close the gas line cock, Remove the burner front cover
and open the control panel door. Switches LS1 and LS2
in the lower right hand corner of the control box should
be in view and the modulating actuator VM1 should be at
the minimum rate position. Verify that the right hand
switch LS1 is being held in the “made” position by the
collar on the control rod and that the switch lever is not
bottomed out against the plastic switch housing.
2. Position the burner switch S3 to AUTO. The flame safe-
guard will go through a 10 second “Initiate” period, after
which the burner motor will start. The modulating gas
valve actuator VM1 will drive the air valve and gas valve
to the maximum rate position. Observe the linkage for
any binding, loose fasteners, or other problems that could
have resulted from shipping.
3. When the actuator reaches the maximum rate position,
verify that the left hand switch LS2 is held in the “made”
position by the collar on the control rod and that the
switch lever is not bottomed out against the plastic switch
housing.
4. Position the burner switch S3 to OFF. Close the control
panel door and reinstall the burner front cover. Prepare to
measure the burner air box pressure by holding a rubber
manometer tube tightly over port (4) in Figure 16b. The
tube must surround the hole and seal tightly against the
burner housing to measure the static pressure through the
hole.
5. Position the burner switch S3 to AUTO and with the
burner actuator VM1 at the maximum rate position mea-
sure the burner air box pressure at port (4) in Figure 16b.
The actuator will remain at this position for the first 20
seconds of the prepurge period. Typical static pressure
readings are listed in Table 7, Column 6. Any appreciable
deviation from these values would indicate a burner air
problem that should be found before attempting to fire
the burner. These problems could include linkages dis-
turbed during shipment, etc.
Flame Start-Up
1. Open the gas line cocks and position switch S3 to AUTO.
The flame safeguard will go through the 10 second “Ini-
tiate” period, after which the burner motor will start. The
modulating air and gas valve actuator VM1 will drive the
air valve to the full open position. At full open the 60 sec-
ond prepurge period will begin. After 20 seconds at maxi-
mum open, the actuator will begin a 30 second stroke to
reposition the air valve back to the minimum position.
Upon completion of the 60 second prepurge cycle, gas
valve GV1 will open (as indicated when the LED marked
PILOT comes on), the ignition transformer is powered
and the flame should come on at minimum rate.
2. Observe the gas manifold pressure manometer during this
sequence. The manifold pressure should be close to zero
(it will indicate a slight heat exchanger pressure caused
by the burner combustion air fan). When gas valve GV1
opens it should indicate a manifold pressure approximate
to the values listed in Table 7, Column 10. Approxi-
mately 3 seconds after GV1 is powered the flame will
come on and the flame signal will read 1.5 to 5.0 volts
DC. The LED marked FLAME will come on when flame
is detected and the LED marked MAIN will come on if
flame is being detected at the end of the 10 second trail
for ignition period. When the LED marked MAIN comes
on gas valves GV4-GV8 (when included) will also open
and the firing rate will be determined by the control sys-
tem. On the initial start-up if the flame does not light and
the flame safeguard locks out, reset it and make several
attempts to light before assuming there are problems
other than more air in the gas lines. If initial flame opera-
tion is erratic wait until after a period of main flame oper-
ation has further purged the gas lines before trying to
“adjust out” something that may actually be caused by air
in the lines.
Modulate Firing Rates
Set the temperature control system so the burner actuator
VM1 will modulate to increase the firing rate. Observe the
flame signal and the manifold pressure manometer as this is
occurring. The flame signal should remain between 1.5 to
5.0 volts DC through the entire range of the burner, and the
manifold pressure should be between the values indicated by
Table 7, Column 9 and 10. If the manifold pressure shoots
above these values and then slowly returns to normal as the
burner is modulating down to a lower firing rate, isolate
which combination gas control is causing this. Check that
valves pressure regulator adjustment per “Gas Valve Pres-
sure Regulator Adjustment” section. If this condition cannot
be adjusted out, replace the valve. If combustion appears
normal, proceed with the combustion test.