HTP EL-399NVWH - Manual (Page 55)

55
LP- 346 REV. 3.20.14
recheck the bus every few seconds as long as it is powered up to update the status of the connected heaters. The control in the master
heater processes all heat demands and dictates which of the follower heaters should light and what firing rate the followers should try to
achieve.
When the master heater receives a demand for heat, it determines which heater is first in the firing sequence and sends that heater a
command to begin a demand sequence. That heater will then begin a demand sequence as described above. Once the heater ignites,
the master heater control will increase the firing rate command to that heater until the system sensor temperature is at the tank set point
temperature plus the supply offset temperature (installer #4), or that heater is at high firing rate. If the command from the master heater
control gets to the high firing rate of the follower heater, but the system sensor is below the required temperature, the master heater
control will then tell the next heater in the firing sequence to begin its demand sequence. The master heater control will then begin to
ramp up the firing rate command of that heater. This process will continue while there is a demand until all heaters 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 installer #4 before all heaters are at high fire, the master control will modulate the cascade command signal to maintain the
system sensor at tank set point and installer #4 until the demand is complete. When the tank temperature is equal to the set point
temperature, the demand is complete, and the master heater control will extinguish all heaters that may be lit. If the demand decreases,
the firing rate command and amount of heaters lit will decrease exactly opposite as described above.
Whenever the master heater control needs to fire a follower heater, it sends a firing rate command to that heater. The follower heater
will respond to the command until its supply sensor temperature gets to be 5
o
F above the tank set point temperature plus the supply
offset temperature (installer #4), at which point the individual heater 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 heaters firing at less than their maximum firing rate.
G. LOCKOUT CONDITION
If any heaters, including the master heater in the cascade system, are in a lockout condition, the master control will recognize the
lockout condition and skip over the heater in the firing sequence. Each heater in the cascade system is responsible for its own safety
functions. So, if any individual heater control senses an unsafe condition, it will extinguish the burner and, if necessary, go to a lockout
condition. In this way, every heater in the system has its individual safety controls intact and operational, even if the firing of the heater
is under control of the master heater.
In the event that the system sensor fails, all heaters in the system will ignite simultaneously when there is a demand, and each heater
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 heater. If this should happen, the master heater will display an E03 fault code, indicating that the supply sensor
has failed.
H. CASCADE SYSTEM PROGRAMMING
1. If the heater is used alone, skip this section.
2. Programming the Master Heater:
a. Make sure there is no demand for heat being supplied to the heater.
b. Apply power to the heater.
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 heater address 0. NOTE: The Master Heater
MUST be addressed as 0.
e. Change Cascade Mode function 23 to 926 Boilrs. This makes it the master heater.
f. Exit the installer menu.
NOTE: The temperature set point of the master must match the follower heater set point in order for the system to operate properly.
3. Programming Follower Heaters:
NOTE: READ THE NOTES BELOW BEFORE PROGRAMMING FOLLOWER HEATERS

The heater addressed as 1 will share its alarm output with the master heater.

It is recommended but not necessary to address heaters in the order that they are wired.

No two heaters can have the same address.

It is not required to use all consecutive address numbers.
a. Make sure there is no demand for heat being supplied to the master heater
b. Apply power to the follower heater 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 heater you are
programming based on the above notes.
e.
Change “CASCADE MODE” parameter to “926 BOILRS”. This makes the heater a follower heater and enables all data to be
transferred between heaters as needed for the system to function to full capability.