Install Instructions

11
6-580.5
START-UP PROCEDURE
3. Move the field installed manual gas shut-off valve to the “ON”
position.
4. Create a high fire call for heat from the thermostat.
5. Determine the correct high fire manifold pressure. For natural
gas 3.5” W.C., for propane gas 10” W.C. Adjust the main
gas pressure regulator spring to achieve the proper manifold
pressure (for location, see the combination gas control
literature supplied with unit).
6. After adjustment, move the field installed manual shut-off
valve to the “OFF” position and replace the 1/8" pipe plug.
7. After the plug is in place, move the field installed manual
shut-off valve to the “ON” position and recheck pipe plugs for
gas leaks with soap solution.
Burner Flame Adjustment
Proper operation provides a soft blue flame with a well-defined
inner core. A lack of primary air will reveal soft yellow-tipped
flames. Excess primary air produces short, well-defined
flames with a tendency to lift off the burner ports. For both
natural and propane gas, the flame may be adjusted by sliding
the manifold. Also, for propane gas, the air shutters can be
adjusted to control the burner flame height. The air shutters
can be accessed by lowering the bottom pan of the unit heater.
Natural Gas Flame Control
Control of burner flames on unit heaters utilizing natural gas is
achieved by resetting the manifold position to either increase
or decrease primary combustion air. Prior to flame adjustment,
operate unit heater for about fifteen minutes. The main burner
flame can be viewed after loosening and pushing aside the gas
designation disc on the back of the unit.
To increase primary air, loosen the manifold mounting screws
and move the manifold away from the burner until the yellow-
tipped flames disappear (see Figure 11.2). To decrease primary
air, move manifold closer to the burner until flames no longer lift
from burner ports, but being careful not to cause yellow tipping.
Retighten manifold mounting screws after adjustment.
Propane Gas Flame Control
An optimum flame will show a slight yellow tip. Prior to flame
adjustment, operate furnace for at least fifteen minutes. Loosen
air shutter set screws and move the air shutters away from the
manifold to reduce the primary air until the yellow flame tips
appear (see Figure 11.3). Then increase the primary air until
yellow tips diminish and a clean blue flame with a well defined
inner cone appears.
It may also be necessary to adjust the manifold position in
addition to adjusting air shutters to obtain proper flame. Follow
the instructions under "Natural Gas Flame Control" for adjusting
the manifold.
Figure 11.1 - Typical Combination Gas Control
GAS CONTROL KNOB
INLET
PRESSURE
TAP
PRESSURE REGULATOR
ADJUSTMENT SCREW
(UNDER CAP SCREW)
OUTLET
PRESSURE
TAP
OUTLET
PILOT TUBING
CONNECTION
PILOT ADJUSTMENT
SCREW
RESET BUTTON
INLET
Figure 11.2 - Manifold Adjustment, Natural Gas
MANIFOLD
MIXER
TUBES
BURNER
RETAINING PIN
MAIN
BURNER
ORIFICES
MANIFOLD MOUNTING
SCREW AND PIN
Figure 11.3 - Air Shutter Adjustment, Propane Gas
MANIFOLD
MIXER
TUBES
MAIN
BURNER
ORIFICES
AIR
SHUTTER
Control Operating Sequence
All units are supplied with intermittent pilot systems with
continuous retry control as standard. For intermittent pilot
systems, both the main burner and pilot are turned off 100%
when the thermostat is satisfied. For all units, the system
will attempt to light the pilot for 70 seconds. If the pilot is not
sensed, the ignition control will wait approximately 6 minutes
with the combination gas control closed and no spark. After 6
minutes, the cycle will begin again. After 3 cycles, some ignition
controllers lockout for approximately 1 hour before the cycle
begins again. This will continue indefinitely until the pilot flame
is sensed or power is interrupted to the system. Refer to Table
12.1 for control code descriptions. Specific descriptions of the
control sequence for different control codes are shown below.
1. The thermostat calls for heat.
2. The power exhauster relay is energized starting the power
exhauster motor. Once the motor has reached full speed, the
differential pressure switch closes.
3. The pilot valve opens and the ignitor sparks for 70 seconds
in an attempt to light the pilot.
4. Once the pilot is lit, the flame sensor proves the pilot and
stops the ignitor from sparking.
5. On single stage units, the main gas valve is opened and the
main burner is lit to 100% full fire. On two stage units, the
gas valve may open at either 50% or 100%, depending on
what the two stage thermostat is calling for.
6. The air mover starts after 30 to 90 seconds to allow the heat
exchanger to warm up.
7. The unit continues to operate until the thermostat is satisfied, at
which time both the main and pilot valves close 100%.
8. The air mover stops after 30 to 90 seconds to remove
residual heat from the heat exchanger.