To Turn Off Gas to Unit
1 − Set thermostat to lowest level.
2 − Turn off all electrical power to unit if service is to
be performed.
3 − Honeywell VR8215 series gas valve, push the
ON-OFF switch to OFF. Do not force. For White
Rodgers 36 series gas valve, move lever to OFF
Heating Sequence of Operation
1 − When the thermostat calls for heat, the
combustion air inducer starts immediately.
2 − Combustion air pressure switch proves inducer
operation before allowing power to the ignition
controller. This switch is factory-set and no
adjustment is necessary.
3 − After prepurge of approximately 30 seconds, the
spark ignition is energized and the solenoid
valves open in the gas valve. HED models 200,
250 and 300 are equipped with a step opening
valve. During ignition phase of start-up a pressure
of approximately 25% of full rate allows even
ignition of all burners for several seconds before
full rate pressure is established.
4 − The spark then ignites the gas, the ignition sensor
proves the flame, and the combustion process
continues.
5 − In the event that the flame is not detected after
the first 10−second trial for ignition, the controller
will repeat steps 3 and 4 an additional two times
before locking out the gas valve. Ignition control
will then automatically repeat steps 3, 4, and 5
after 60 minutes.
NOTE
: To interrupt the 60−minute lockout period, move
thermostat from Heat" to OFF" then back to Heat."
Heating sequence then restarts at step 1.
6 − The burners must light without noticeable crossover
delay. There must be no flame lifting from the burner
heads, flashback or burning within the burner. The
flames should be predominantly blue in color and
should be approximately centered in the tubes with
no apparent impingement taking place.
7 − The ignition control will energize the ACC
terminals approximately 45 seconds after ignition
is established.
8 − After the thermostat demand is satisfied, the gas
valve is closed. Five seconds after the demand is
satisfied, the combustion air inducer is shut off.
9 − The ignition control will de-energize the ACC
terminals approximately 150 seconds after the
gas valve is de-energized.
Ignition Control LED
The ignition control contains a green LED which
indicates the following:
TABLE 6
IGNITION CONTROL LED
LED
UNIT OPERATION
Slow
Normal Operation − No call for heat
Flash*
Fast
Normal Operation − Call for heat
Flash
2
System lockout − failed to detect or sustain
Flashes
flame
3
Pressure switch failed closed before CAI is en-
Flashes
ergized or failed open after CAI is energized
4
High limit or rollout switch open
Flashes
5
Flame sensed and gas valve not energized
Flashes
Steady
Loss of power
Off
Steady
Ignition control failure
On
*When thermostat is placed in continuous fan mode, LED will
slowly flash.
High Altitude Adjustment
In Canada, certification for installation at altitudes over
4500 feet (1372m) above sea level is the jurisdiction of
the local authorities.
Unit may be fired at full input up to 2000 feet (610m)
above sea level. At altitudes of 2000-4500 feet
(610−1372m) units have a fixed derate. See markings
on unit for correct input. No additional adjustment is
necessary. If unit is installed at an altitude greater than
4500 ft. (1372m), unit must be derated by 4 percent for
each additional 1000 ft. (305m) above sea level or as
permitted by the requirements of the local authorities.
NOTE
− A natural to LP/propane gas changeover kit is
required to convert the unit in the field. Refer to the
installation instructions supplied with the changeover kit
for conversion procedure.
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