40
•
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 status of switch inputs and output
states. An asterisk (*) is displayed next to label when status is
“True” (the description is fulfilled). For example, if water is flowing,
or detected by flow sensor, then an “*” will appear in front of Flow
label (i.e. *Flow). Another example would be the MRHL switch.
If outlet temperature is too high the display will show: *MRHL.
The System monitors the inputs at these times:
• 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 pump is on (no check for off state)
• Blower Prover - Pre and Post purge.
• 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.
• Blocked Flue, Blocked Inlet during heating mode
Control Status Screen:
Displays 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 system waits for a
heat request (determined by Thermostat or controlling probe
inputs). All outputs are off in this state except that if Post-
Circulate time is set to continuous, pump will be on. When heat
request is received, system moves to 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 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 heat request is satisfied, Tstat is opened, or a
fault occurs.
• Soft Fault State: (See “Fault Description” section for list of soft
and Auto Reset faults.)
Pump remains on for selected post-circulate time to cycle hot water
out of boiler. The FCB is commanded to shut down and Alarm
output is turned on. Green LED turns off and red “Service” turns
on. MCB remains in this state until one of 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.
The process waits in this state until the call for heat is satisfied, the
thermostat input is opened, or a fault occurs. When heat is satisfied,
the sequence continues to Post-Purge and then back to Idle. If
three tries for ignition has been selected on the MCB dipswitch and
flame is not detected at the appropriate time, then the sequence
moves to the Inter-Purge state for 15 seconds and the FCB heat
sequence is repeated. If flame is still not detected after the third try
the process declares a fault, jumps out of sequence and goes to
the error state. Other types of faults detected at any time will also
cause a jump to the error state.
Description of FCB control states:
• Idle State:
When any error is declared during idle state-The system will
remain in this state until the MCB request a heating cycle, or a
cold purge.
• Pre-Purge State:
The blower is turned on. After 10 to 34 seconds (34 seconds for
cold purging) the system switches to the Heat Igniter State.
• Heat Igniter State:
Sequence of operation is as follows: “The igniter relay is
energized and heat up period begins. After 18-20 seconds, if
igniter has reached a minimum of 2.8 amps, gas valve safety
circuit is then activated. If in this amount of time, igniter fails to
reach a minimum amp draw of 2.8 amps, unit will re-cycle up to 3
times before locking out on igniter hardware failure. If igniter does
reach minimum required amp draw of 2.8 amps, gas valve circuit
is energized, and system advances to Flame Check status.
• Check for Flame State:
The gas valve is turned on. After 1.5 seconds, the system
checks that the gas valve relay is on. If it is not, the ignition
trial is considered to have failed and the system advances to
the Inter-Purge state, if any ignition trials remain, otherwise an
error is declared.
The flame sensor is checked. If flame is detected, the igniter
is turned off. The state machine then advances to the Heating
State. If after 5 seconds, the flame is still not sensed then the
ignition trial is considered to have failed. The state machine
advances to Inter-Purge if any ignition trials remain, otherwise
an error is declared.
• Heating State:
The system remains in this state until the call for heat is
cancelled or a fault occurs. The system returns to the Idle state
if the call for heat is cancelled, or satisfied and to the appropriate
fault state if a fault occur.
• Inter-Purge State:
The gas valve and the igniter are turned off. The blower is on.
After approximately 15 seconds the system goes back to the
Heating Igniter State.
• Post-Purge State
The gas valve and the igniter are turned off. If this stage
does not have a blower the system returns to the idle
state. If it does have a blower then the blower is left on.
After approximately 25 seconds, the system returns to
the Idle state.
• Error State
The gas valve and the igniter are turned off. The FCB micro tells
the MCB micro which error has occurred. The system waits in
Содержание VB/VW 1500, 2000
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