CleaverBrooks CFC-500 Operation, Service And Parts Manual page 147

CH ENABLE
DHW ENABLE
LL SLAVE ENABLE
PRIORITY: CH <>DWH LL<>DHW
DHW PRIORITY OVERRIDE TIME
CH FROST PROTECTION ENABLE
DHW FROST PROTECTION ENABLE
CH BURNER DEMAND
DHW BURNER DEMAND
LL SLAVE DEMAND
FROST BURNER DEMAND
OFF (NO DEMAND) = 0
CH RATE
DHW RATE
LL SLAVE RATE
FROST PROTECTION RATE
OFF (NO DEMAND) = 0%
INLET
OUTLET
The demand priority control block shown in Fig. 5 determines
which source of demand has control of the burner, according to
parameters and the logic described below.
IF "DHW pump demand" is true
Set DHW_storage_timer to DHW storage time
ELSE
Decrement DHW_storage_timer (count down to zero, then stop)
IF "DHW pump demand" is false
Set DHW_priority_timer to DHW priority override time
ELSE
Decrement DHW_priority_timer (count down to zero, then stop)
DEMAND
PRIORITY
CONTROL
RELOAD
DHW
demand
priority
timer
CH
DHW
BURNER DEMAND
LL
FP
RATE LIMITS
OFF
pRATE TO mRATE
CONVERSION
CH
DHW
REDUCE:
LL
DELTA-T ...
FP
STACK LIMIT ...
OFF
SLOW START ...
FORCED RATE...
STACK
BOOST:
MIN. MOD. RATE
ANTI-CONDENS...
ANTI-CONDENSATION
PRIORITY
Fig. 5. Demand and rate selection diagram.
Fig. 6. DHW priority timer logic.
SLAVE COMMAND EXISTS
CH PUMP DEMAND
DHW PUMP DEMAND
CH FROST PROTECT BURNER DEMAND
DHW FROST PROTECT BURNER DEMAND
PUMP
CONTROL
MANUAL RATE ENABLE
- AUTO
- MANUAL IN RUN
- MANUAL IN RUN AND STANDBY
MANUAL
RATE
RATE OVERRIDE
OVERRIDE
LIMITS
0 = BC HAS COMMANDED FAN TO BE OFF & NOT BELOW; OR BC DISABLED/FAULT.
MIN. MOD. RATE = MANUAL RATE WHEN FIRING IS LESS THAN MINIMUM MODULATION,
OR ABNORMAL BC REQUEST (MANUAL MODES IGNORED).
MAX. MOD. RATE = MANUAL RATE WHEN FIRING IS GREATER THAN MAX MODULATION.
= ABNORMAL BC REQUEST OR MANUAL IN STANDBY IS LESS THAN ABS. MIN.
ABS. MIN. RATE
ABS. MAX. RATE = ABNORMAL BC REQUEST OR MANUAL IN STANDBY IS LESS THAN ABS. MIN.
TOP: FIRING & BC HAS NO COMMANDED RATE & ONE OF THE MANUAL MODES IS ENABLED.
OR
NOT FIRING & BC IS IN STANDBY & "MANUAL IN RUN & STANDBY" IS ENABLED.
MIDDLE: NOT ABOVE AND BC HAS A COMMANDED RATE (E.G. IN STANDBY, PURGE, IDNITION, ETC.)
BOTTOM: FIRING & BC HAS NO COMMANDED RATE & AUTO MODE SELECTED (NORMAL MODULATION)
The DHW priority timer within this block operates according to
the logic:
23
SENSOR
TERMINALS
INPUT OUTPUT
PARAMETER
"pRATE" = 0 TO 99.99% OF CAPACITY
"mRATE" = ANALOG% OR RPM
BURNER DEMAND
BURNER STATUS BURNER
CONTROL
COMMANDED RATE
MODULATION
4-20mA
OUTPUT
ANALOG PERCENTAGE
OUTPUT
SELECT
0-10V
MIN/MAX FAN
SPEED LIMIT
TACH
MIN PWM
LIMIT
FAN SPEED
PWM
RAMP
FIRING RATE
CB FALCON
750-265