Crown Boiler BWF Series, Supplement Manual

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12
F-C
(Temperature Units ) - Determines whether temperature units on the S9361A are displayed in F or C. Note that this selection
only applies to the temperature displayed on the LED shown in Figure 10b.0. Temperature units must be selected independently
on the displays of any control options plugged into Option Plugs 1 or 2.
bAc
(Return to Status mode) - Exits adjustment mode. Any changes made to the parameters described above are saved, and
become effective, as soon as they are made; bAc only exits adjustment mode.
D. Sequence of Operation
(Refer to Figures 9.2 or 9.3 for Connection and Ladder diagrams)
A call for heat from the thermostat connected to the themostat leads energizes the Heating Circulator (connected to red and 1)
white leads in J-box).
Depending on the boiler water temperature at the time of the call for heat, the control will do one of two things: 2)
If the water temperature is below the thermal purge start temperature ( •
St
), the control will continue the ignition se -
quence.
If the boiler water temperature is above the thermal purge start temperature, the boiler will wait until either of the follow - •
ing conditions are met before continuing the ignition sequence:
The boiler water temperature falls below the thermal purge start temperature ( a)
St
) Factory default is 140F.
The thermal purge time elapses ( b)
PP
). Factory default is 2 minutes.
If the flame roll-out switch, and LWCO contacts are made, the control will verify that the air pressure switch (APS) is open 3)
before starting the fan.
The control enegrgizes the fan and waits for the air pressure switch to close. 4)
Once the air pressure switch closes, the control waits for a 30s “prepurge period” to pass before attempting to light the pilot. 5)
The control starts an ignition spark at the pilot and applies 24 volts across the pilot valve (terminals PV and MV/PV on the 6)
gas valve).
Once the pilot is established, the pilot flame will act as a diode, converting the AC current at the electrode to a half wave DC 7)
current at the pilot’s ground strap. This DC current flows through the boiler to the ground connection on the S9361A. For
the ignition module to recognize that a pilot flame is present, the DC current flowing into this terminal must be in excess of
approximately 1.0 uA .
If the pilot is not proven within 60 seconds of the beginning of the trial for ignition, the pilot valve will close and wait 5 min - 8)
utes before the ignition sequence is retried.
Once the ignition module detects the presence of a pilot flame, voltage is applied across the main valve (terminals MV and 9)
MV/PV on the valve), opening the valve and establishing main flame.
If the water temperature climbs above the high limit setting during the call for heat, the burner and blower will shut down 10)
TABLE 10b .7: SUMMARY OF CIRCULATOR BEHAVIOR
Thermostat Inputs
Use of
“DHW”
Zone
Parameters Circulator Outputs
T-T “DHW”
2nd Zone
(
dh
)
DHW
Priority
(
Pt
)
Heating
(Red Circ. Lead)
“DHW”
(Blue Circ. Lead)
ON OFF DHW dh=
dh ON
ON OFF
OFF ON DHW
dh=
dh ON
OFF ON
ON ON DHW dh=
dh ON
OFF ON
ON ON DHW dh=
dh OFF
ON ON
ON OFF DHW dh=
dh OFF
ON OFF
OFF ON DHW dh=
dh OFF
OFF ON
ON OFF Heat dh=
tt2 ON
or
OFF
ON OFF
OFF ON Heat dh=
tt2 ON
or
OFF
OFF ON
ON ON Heat dh=
tt2 ON
or
OFF
ON ON