Boiler Parameter Worksheet
Appendix
37
If the header temperature exceeds the “HDR SETPOINT” plus “HYST STOP BLR”, the master boiler starts the
“WAIT BLR SWITCH OFF” timer. If at the end of the timer, the header temperature still exceeds the “HDR
SETPOINT” plus “HYST STOP BLR”, the last active boiler will be disabled. When the timer reaches 0:00 and a
boiler is disabled, the timer immediately resets and resumes counting down. This timer pauses when the header
temperature is between the “HYST START BLR” and “HYST STOP BLR”. If at any time the header temperature
exceeds the “HDR SETPOINT” plus “HYST STOP BLR”, the timer resumes its countdown from the last paused
time and will not reset until it eventually reaches 0:00.
This process can continue until only the lead boiler remains online. If just the lead boiler is online and the header
temperature still exceeds the “HDR SETPOINT” plus “HYST STOP BLR”, the lead boiler will return to standby.
If “WAIT RESET TIME” is ON then the timer resets to 0 every time a reduction in heat load occurs. If “WAIT
RESET TIME” is OFF then the timer pauses time for sequence every time a reduction in heat load occurs. Once
it reaches 0, then it resets.
1.8.5.1.2 Lead Rotation
The lead boiler will rotate position based on the “START ROTATION” parameter. After the lead boiler has operated
for the defined number of accumulated time, the lead position will rotate to another boiler. The time setting value can
be set from 1 to 255 hours with ver. 8C51 and prior; or 1 to 255 days using version 1043 or 9820. This function can be
disabled by changing “START ROTATION” to off, in which the master boiler will always operate as the lead boiler.
1.8.5.1.3 Quick Start and Quick Stop
If the system experiences rapid changes in temperature, it may be necessary to start or stop boilers at an accelerated
pace. If the header temperature drops below the “HDR SETPOINT” minus the “HYS QUIC START”, the master boiler
will begin the “QUIC START TIME” timer, which will bypass the “WAIT BLR SW ON” timer.
Once
“QUIC START TIME” timer expires and the temperature condition is still true, a boiler will be requested for
cascade operation. This quick start process can continue until all the boilers are online if the low temperature
condition remains.
Similarly, if the header temperature exceeds the “HDR SETPOINT” plus the “HYS QUIC STOP”, the master boiler will
begin the “QUIC STOP TIME” timer, which will bypass the “WAIT BLR SW OFF” timer. Once this timer expires, if the
temperature condition is still true, a boiler will be removed from cascade operation. This quick stop process can
continue until all the boilers are offline if the high temperature condition remains.
1.8.5.1.4 Hybrid systems setup
In a hybrid system that contains both condensing and non-condensing boilers, cascade settings help prevent the non-
condensing boilers from operating in a condensing mode. The CSC MIN RET T is the minimum return temperature
setting. The factory default CSC MIN RET T setting for P-K MODU-FIRE
®
FD boilers is 122°F. Each member boiler
checks that the return water temperature is greater than the CSC MIN RET T plus the HYST MIN RET T. If the return
temperature is too low, the non-condensing boiler signals the Master ENVI
®
control to skip this boiler.
If a condensing boiler cannot be found, the Master ENVI
®
control goes into NO BLR ON WAIT. When the NO BLR
ON WAIT time period expires, the first available boiler will start and burn at high fire until the boiler inlet temperature is
greater than RET T MAX PWR. If the return water temperature remains below CSC MIN RET T, the NO BLR ON
WAIT sequence repeats. When the return temperature exceeds RET T MIN PWR, the boilers release to modulate
according to the master controller. Other boilers in the member network may be enabled and modulated to meet the
load.
NOTICE! The Master ENVI
®
control will not override individual boiler protective parameters. For example, MOD
BACK DIFF will still prevent the member boiler from exceeding the temperature differential setting.
