15
SECTION III
OPERATION AND TROUBLESHOOTING
SEQUENCE OF OPERATION – EHG POWER GAS BURNER UTILIZING HONEYWELL S89F GAS
PRIMARY W/BUILT IN 30 SECOND PREPURGE
On a call for heat, voltage (24VAC) is applied to the motor start relay and air switch. Once the fan motor
reaches operating rpm, the available combustion air will close the air-proving switch contacts, energizing the
gas primary control.
The S89F gas primary control has an internal 30-second pre-purge timer. After the initial 30 second pre-purge,
an internal 8-second safe start check of the S89F will commence. Once this is successfully completed, the
S89F simultaneously energizes the gas valves and ignition transformer. Gas flows and the transformer
produces an approximate 15,000 volt spark end point grounded at the burner head establishing main burner
flame.
At the start of each heat cycle, there is a trial for ignition period of four (4) seconds duration. Normally, burner
flame will be established before the end of this period. Once the flame is established, sparking will cease and
the flame rod will provide flame monitoring to the S89F gas control primary for the remainder of the heat cycle.
If the flame should be extinguished during the heat cycle, the S89F gas control primary will go into the 30
second pre-purge and 8 second safe start check, then re-energize the gas valve and ignition transformer in an
attempt to establish the main burner flame. If this does not occur within the 4-second trial for ignition period,
the S89F gas primary control will go into lockout de-energizing the gas valves and ignition transformer.
To restart the system, the main power or thermostat must be de-energized momentarily, then re-energized. If
at any time during the heat cycle, there is a failure of the combustion air supply to the burner, the air switch will
open, putting the system into lockout, closing the gas valves.
EHG POWER GAS BURNER
WITH HONEYWELL S89F GAS PRIMARY
AND GAS VALVE/REGULATOR COMBINATION
Figure 10
To Next Page
Loading...
