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the temperature is less than the operating setpoint minus the
differential temperature and the thermostat input is closed then
a call for heat is established and the system shifts to the run
mode (green "Running" LED turns on).
5. The heating sequence begins by applying power to the pump.
6. After a few seconds the blower is turned on for 30-second
pre-purge period of combustion chamber.
7. The igniter is turned on.
8. After the igniter has reached a minimum of 2.8 amps, the gas
valve is energized to allow gas flow to burner.
9. After an additional one second, the system checks the status
of the flame through the flame rod (sensor). If the flame is
not verified within 4 seconds, the gas valve is immediately
shut off followed by 15-second inter-purge period, then the
system returns to step 7, if the "Trial for Ignition" dipswitch is
set for three (3) tries. If the dipswitch is set for one (1) trial,
the system will declare an error and boiler will require
resetting the control.
10. The boiler will remain running until the set point is satisfied.
Once satisfied, the blower will continue for 15-second post
purge period.
11. Once set point has have been satisfied, the boiler pump will
continue to run for the programmed post-circulate cycle.
12. The control now enters the idle state as displayed by the
"Standby" LED. The control will continue to monitor heat
demand and state of other system devices. Upon a drop of
water temperature below the set parameters, the control will
return to step 5 and repeat the entire operating cycle. Note:
Any fault detection, during standby or running modes, will
halt the heating sequence and shift the system to the service
mode where the detected fault will be displayed.
NOTE: In standby and running modes the system constantly
monitors the signals and the internal operation for faults. Any
detected fault will halt the heating sequence and shift the system
to the service mode, where the detected fault will be displayed.
TEMPERA TURE SETPOINTS (SYSTEM CONTROL ALGORITHM)
The boiler has a hysteresis type control, which means that it will
begin heating the water when the temperature sensed by the
control probe (inlet or tank) falls below the operating setpoint
minus the differential setpoint. It will stop heating the water when
the temperature rises to the operating setpoint.
UIM OPERATING PROCEDURES
UIM, USER INTERFACE MODULE
The UIM receives commands from the user and displays
operational information to the user via an LCD (liquid crystal
display) up to eleven LED's, and five touch switches. The LCD
provides information to the user by the use of 10 menu-activated
screens. Within each of the screens, helpful information can be
displayed by pressing the "Help" button. The LED's visually inform
the user about the mode the system is in. The touch switches
allow the user to control the operation of the system. The operation
of these parts is described in the following section:
UIM Screens:
On all screens a double vertical bar appears on the right side of
the display each time a key is touched to indicate that a key has
been activated. On several screens an indicator ">" appears on
the left side of the display to indicate the active line. The "Up/
Down" keys are used to move the indicator to the desired line and
the "Select" key is pressed to select the line. Also, on most of the
screens, up/down arrows appear on the right side of the screen to
indicate that there is additional lines either above or below the
displayed four lines.
• Menu Screen:
Displayed when the user presses the "Menu" key. This screen
is the selection point for the other 9 screens.
• Temperature Screen:
Displays the sensed temperatures of the Outlet, Inlet, and Tank
probes. Also displayed is the calculated Delta T (Outlet minus
Inlet) for the system. Shorted ("Short") and disconnected
("----") probes are also displayed.
• System Status Screen:
This screen is used to view the status of switch inputs and output
states. An asterisk (*) is displayed next to the label when the
status is "True" (the description is fulfilled). For example, if
water is flowing, or detected by the flow sensor, then an "*" will
appear in front of the Flow label (i.e. *Flow). Another example
would be the ECO switch. If the outlet temperature is too high
the display will show: *ECO.
The System monitors the inputs at these times:
• ECO, Blocked Flue, Low Gas, Hi Limit, and Hi Gas - at all times
for a fault condition.
• Tstat - at all times for open/closed conditions.
• Flow-for an on condition when the pump is on (no check for
off state)
• Blower Prover - when the Blower is on.
• Igniter Current - for an on condition approximately 18 seconds
after the Igniter is turned on until the igniter is turned off and an
off condition at all other times.
• Flame - for an on condition approximately 5 seconds after the
gas valve is turned on until the valve is turned off and at all
other times for an off condition.
Control Status Screen:
Displays the status that the MCB micros are in. The MCB has 5
possible states and the FCB have 9. The normal MCB states
sequence is to move from Idle to Pre-Circulate when a call for heat
is initiated. Once heat has been satisfied or the Thermostat is opened,
the sequence moves to Post-Circulate and then back to Idle. If a
fault occurs at any time, the process jumps out of sequence and
goes directly to the appropriate Hard or Soft Fault state.
Description of MCB control states:
• Idle:
The yellow "Standby" LED is turned on and the system