HTP EL-80 - Setting up a Cascaded System; Lockout Condition; Cascade System Programming

LP-293 Rev. 9.24.15
45
J. Setting Up a Cascaded System
If the boiler is part of a cascaded system the operation is
somewhat dierent. 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
ring rate the followers should try to achieve.
When the master boiler receives a demand for heat, it
determines which boiler is rst in the ring 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 ring rate command to that boiler until the system
sensor temperature is at the set point temperature plus the
dierential, or that boiler is at high ring rate. If the command
from the master boiler control gets to the high ring 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 ring sequence to begin its demand sequence.
The master boiler control will then begin to ramp up the ring
rate command of that boiler. This process will continue while
there is a demand until all boilers in the cascade system are
at high re or the desired temperature of the system sensor
is reached. If the system sensor temperature reaches tank
set point and dierential before all boilers are at high re, the
master control will modulate the cascade command signal to
maintain the system sensor at set point and dierential 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 ring rate command and amount
of boilers lit will decrease exactly opposite as described above.
Whenever the master boiler control needs to re a follower
boiler, it sends a ring rate command to that boiler. The follower
boiler will respond to the command until its supply sensor
temperature gets to be 5
o
F above the set point temperature
plus the dierential, 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 ring at less than their maximum ring 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 ring 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 ring of the boiler is under
control of the master boiler.
In the event that the system sensor fails, all boilers in the
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 926 Boilrs. This
makes it the master boiler.
f. Exit the installer menu.
NOTE: The temperature set point of the master must match
the follower boiler set point in order for the system to operate
properly.
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 red 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).
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 rst follower,
2 for the second follower, etc. depending on which boiler you
are programming based on the above notes.
e. Change “CASCADE MODE” parameter to “926 BOILRS”.
This makes the boiler a follower boiler and enables all data
to be transferred between boilers as needed for the system
to function to full capability.
f. Exit the installer menu.
NOTE: The temperature set point of the follower must match
the master boiler set point in order for the system to operate
properly.
system will ignite simultaneously when there is a demand, and
each boiler will individually regulate ring rates to maintain the
master set point temperature (supply temperature set point +
dierential) 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.