Sterling QVES - Manual (Page 18)

18
OPERATION
POWER VENTED DUCT FURNACES WITH INTERMITTENT (SPARK) PILOT IGNITION
It is the installer’s responsibility
to check all safety controls! Check and test
the operational functions of all safety devices
supplied with this unit, and ensure that all are
operating effectively. Failure to do so could
result in unsafe conditions and may result in
death, serious injury or property damage.
EXPLANATION OF CONTROLS:
1. The duct furnace is equipped with a dual automatic
gas valve and electric ignition device (separate from
the gas valve on most models) which provide the
following functions:
a. The duct furnace is equipped with a power
vent system consisting of a power venter motor
and blower, pressure switch, and sealed flue
collector in place of the conventional draft
diverter.
Never operate the unit beyond the
specifi ed limits, severe damage to, and/or premature
failure of the unit will result!
b. The power venter motor is energized by the
room thermostat on a call for heat. The pressure
switch measures the flow through the vent
system and energizes the indirect spark ignition
system when the fl ow is correct.
The pressure switch MUST NOT
be bypassed. The unit MUST NOT be fired
unless the power venter is operating. An unsafe
condition could result.
The addition of external draft hoods
or power venters is not permitted. Addition of such
devices may cause serious unit malfunction or
failure or possible personal injury.
c. The intermittent pilot ignition system consists of
an ignition control module, a dual combination
gas valve, and a spark-ignited pilot burner.
When the pressure switch closes, the pilot
valve opens and a spark is generated to light
the pilot burner. When the fl ame sensing circuit
senses that pilot fl ame is established, the main
gas valve is opened to supply gas to the main
burners. When the thermostat is satisfi ed, the
vent system is de-energized and both valves
are closed to stop all fl ow of gas to the unit.
d. Pilot solenoid valve also functions as a main
gas valve to provide redundancy.
e. Pressure regulator provides proper and steady
gas pressure to the main burners.
f. Manual shutoff valve for service and long term
shut-down. (Separate from the automatic valve
on some models.)
2. The high limit switch interrupts the fl ow of electric
current to the main gas valve in case the heater
becomes overheated.
3. The fan switch delays the operation of the fan until
the heater is warmed, then keeps the fan running
after the gas has been turned off until the useful heat
has been removed. The start-up fan delay must
not exceed 90 seconds from a cold start.
4. The wall ther mostat (supplied optionally) is a
temperature sensitive switch which operates the
vent system and ignition system; it turns the main
gas valve ON or OFF to control the temperature of
the space being heated. It must be mounted on a
vibration free, vertical surface away from air currents,
in accordance with the instructions furnished with
the thermostat (also refer to Electrical Section).
START-UP
1. Open the manual valve supplying gas to the unit
heater, and with the union connection loose, purge
air from the gas line. Tighten the union and check
for gas leaks, using a soapy water solution only.
Never use an open flame to
detect gas leaks. Explosive conditions may exist
which would result in personal injury or death.
Before attempting to light or
relight pilot, wait 5 minutes to allow gas which
may have accumulated in the burner compart-
ment to escape. Failure to do so could cause
the accumulated gas to ignite rapidly, leading to
personal injury or death.
2. Open the manual valve on the unit heater.
3. Turn ON electrical power.
4. The unit should be under the control of the
thermostat. Turn the thermostat to the highest point
and determine that the power venter motor starts
and the pilot and main burners ignite. Turn the
thermostat to the lowest point and determine that
the power venter motor shuts off and pilot and main
burners are extinguished.
5. If pilot adjustment is required, remove the pilot
adjustment seal cap and adjust the pilot screw to
obtain proper fl ame. Clockwise rotation decreases
pilot fl ame size. Replace the cap.
6. Turn the thermostat to the desired position.
7. Refer to “Adjustments” section for more specifi-
cations.
SHUT DOWN
1. Turn the valve selector knob to the “OFF” position.
2. Turn off the electricity.
3. To relight, follow the “start-up” instructions.
See Figure 15 for burner component parts/identifi cation.