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from the combustion chamber. In addition, the pump will run for a
pump post purge interval. The control will then be in standby, waiting
to process the next demand for heat.
During this process, the control will extinguish the burner if it senses
a dangerous or unsafe condition. If the control determines that a
dangerous or unsafe condition has occurred, the control may lock out
the boiler and prevent it from igniting until a maintenance person
diagnoses the problem, repairs it, and resets the control. In the event
that the control goes into lockout, it will show a diagnostic code on
the display, illuminate the LED fault indicator, and close the alarm relay
contacts to aid in recognition of the condition, diagnosis, and repair.
J. Setting Up a Cascaded System
If the boiler is part of a cascaded system the operation is somewhat
different. The control of each boiler in a cascaded system completes its
own power up system check. One of the boilers in the cascade system
is designated as the master boiler. After the master boiler completes
its power up sequence, it checks the communication bus to see if
any other boilers are present. If other boilers are present, the master
control determines these follower boiler addresses. The master boiler
control will recheck the bus every few seconds as long as it is powered
up to update the status of the connected boilers. The control in the
master boiler processes all heat demands and dictates which of the
follower boilers should light and what firing rate the followers should
try to achieve.
When the master boiler receives a demand for heat, it determines which
boiler is first in the firing sequence and sends that boiler a command
to begin a demand sequence. That boiler will then begin a demand
sequence as described above. Once the boiler ignites, the master
boiler control will increase the firing rate command to that boiler until
the system sensor temperature is at the set point temperature plus the
differential, or that boiler is at high firing rate. If the command from the
master boiler control gets to the high firing rate of the follower boiler,
but the system sensor is below the required temperature, the master
boiler control will then tell the next boiler in the firing sequence to
begin its demand sequence. The master boiler control will then begin
to ramp up the firing rate command of that boiler. This process will
continue while there is a demand until all boilers in the cascade
system are at high fire or the desired temperature of the system sensor
is reached. If the system sensor temperature reaches tank set point
and differential before all boilers are at high fire, the master control
will modulate the cascade command signal to maintain the system
sensor at set point and differential until the demand is complete.
When the system sensor is equal to the set point temperature, demand
is complete, and the master boiler control will extinguish all boilers
that may be lit. If the demand decreases, the firing rate command and
amount of boilers lit will decrease exactly opposite as described above.
Whenever the master boiler control needs to fire a follower boiler, it
sends a firing rate command to that boiler. The follower boiler will
respond to the command until its supply sensor temperature gets
o
to be 5
F above the set point temperature plus the differential, at
which point the individual boiler will modulate on its own so as not
to overheat. As a result, it is not uncommon to see the cascade output
at maximum but individual boilers firing at less than their maximum
firing rate.
K. Lockout Condition
If any boilers, including the master boiler in the cascade system, are
in a lockout condition, the master control will recognize the lockout
condition and skip over the boiler in the firing sequence. Each boiler
in the cascade system is responsible for its own safety functions.
So, if any individual boiler control senses an unsafe condition, it will
extinguish the burner and, if necessary, go to a lockout condition. In
this way, every boiler in the system has its individual safety controls
intact and operational, even if the firing of the boiler is under control
of the master boiler.
In the event that the system sensor fails, all boilers in the system will
ignite simultaneously when there is a demand, and each boiler will
individually regulate firing rates to maintain the master set point
temperature (tank set point + installer #4) at the individual supply
sensors built into the boiler. If this should happen, the master boiler
will display an E03 fault code, indicating that the supply sensor has
failed.
L. Cascade System Programming
1. If the boiler is used alone, skip this section.
2. Programming the Master Boiler:
a. Make sure there is no demand for heat being supplied to the
boiler.
b. Apply power to the boiler.
c. Enter the system setting program navigation following
instructions in Part 10 of this manual.
d. Verify that cascade address function 15 is set to 0. This makes
the master boiler address 0. NOTE: The Master Boiler MUST be
addressed as 0.
e. Change Cascade Mode function 23 to ALL 926 if cascade
system IS NOT common vented. If cascade system IS common
vented, set Function 23 to the total number of boilers in the
system (4 BOILERS for a four boiler system, 6 BOILERS for a six
boiler system, etc.)
f. Exit the installer menu.
3. Programming Follower Boilers:
NOTE: READ THE NOTES BELOW BEFORE PROGRAMMING
FOLLOWER BOILERS
•
The boiler addressed as 1 will share its alarm output with the
master boiler.
•
If one of the follower boilers has an indirect fired water
heater connected to it, the address of this boiler must be 2
or greater.
•
It is recommended but not necessary to address boilers in
the order that they are wired.
•
No two boilers can have the same address.
•
It is not required to use all consecutive address numbers.
Example: In a 2 boiler system with an indirect connected to
the follower, the follower address would be 2 (address 1 is
not used).
•
Maximum amount of boilers in a cascaded system is eight
(8).
a. Make sure there is no demand for heat being supplied to the
master boiler.
b. Apply power to the follower boiler you are working on.
c. Enter system settings following instructions in Part 10 of this
manual.
d. Set cascade address parameter 15 to 1 for the first follower,
2 for the second follower, etc. depending on which boiler you
are programming based on the above notes. This establishes
the boiler as a follower in a cascaded system and enables data
to be transferred as needed for the system to function at full
capability.
NOTE: ONLY select number 8 IF you are using a Vision 3 panel for
cascade operations instead of a master boiler.
e. Change "CASCADE MODE" Function 23 to parameter to "ALL
926" if the cascade system is not to be common vented. If the
cascade system IS to be common vented, set Function 23 to
"COMMON FLUE".
f. Exit the installer menu.
whl-445 Rev. 000 Rel. 014 Date 7.21.20
41
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