Water; Uim Operating Procedures - A.O. Smith VB-500, VB-750 Instruction Manual

UIM OPERATING PROCEDURES

FIGURE 20. 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 of these times:
• MRHL, Blocked Inlet, 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 waits
for a heat request (determined by the Thermostat or controlling
probe inputs). All outputs are off in this state except that if the
Post-Circulate time is set to continuous, the pump will be on.
When the heat request is received, the system moves to the
Pre-Circulate state.
• Pre-Circulate:
The yellow LED is turned off and the green "Running" LED is
turned on. The green LED will remain on for all other states
except the fault states. Cold purging clears out any combustion
gas that may be in the combustion chamber. When purging is
complete the system moves to the Heat State.
• Heat Stage
The system will command the FCB micros to start their heat
sequence. will be activated in order based on an algorithm that
determines how much heat is needed. The system will remain in
this state until the heat request is satisfied, the Tstat is opened,
or a fault occurs.
• Soft Fault State: (See "Fault Description" section for list of soft
and Auto Reset faults.)
The pump remains on for the selected post-circulate time to
cycle the hot water out of the boiler. The FCB is commanded
to shut down and the Alarm output is turned on. The green LED
turns off and the red "Service" turns on. The MCB remains in
this state until one of the following occurs:
• One hour passes (automatic restart after one hour)
• If Communications error system will automatically
restart if communications re-establishes.
• If user presses Select key while current error screen is
displayed (Hard reset).
• If high-limit error - the outlet temperature drops below the
high limit trip point minus the high limit differential. (outlet
water temperature drops to safe level). The fault is logged
in the error history when the fault state is exited.
• Hard Fault State: (See "Fault Description" section for list of
soft and Auto Reset faults.) The pump remains on for the
selected post-circulate time to cycle the hot water out of the
boiler. The FCB is commanded to shut down and the Alarm
output is turned on. The green LED turns off and the red
"Service" turns on and off (flashes). The only way to exit
this state is for the user to press the Select key while the
current error screen is displayed. The fault is logged in the
error history when the fault state is exited.
While the MCB is in the Heating mode the FCB moves from Idle, to
Pre-Purge, to Heat Igniter, to Check for Flame, and then to Heating.
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