AERCO BMS II BOILER - Manual (Page 43)

OPERATION
3-11
Sequential
When SEQUENTIAL MODE is selected it provides a greater turn-down ratio than the PARALLEL MODE.
This is due to the fact that the turn-down ratio in the Sequential Mode is equal to the number of Boilers
multiplied by the 20 for KC1000 Series and Benchmark Series units.
In Sequential Mode, each boiler is started one at a time based on the load and start/stop levels
programmed in the BMS. The BMS will start a single Modulex boiler when there is a load demand or a
Benchmark or KC1000 boiler when the boiler start level is reached. Once the first boiler reaches twicethe
start level, a second boiler will be started and the load will be distributed evenly between the two boilers.
For instance, if a start level of 25% is chosen, when the first boiler reaches 50% a second boiler will start
(after a 30 second delay), and the BMS will distribute the load 25% for each boiler. If the firing rate of both
boilers reach a combined value equal to 3 times the start level, a third boiler is started by the BMS (after a
30 second delay), and the load will be distributed across all three boilers. This sequence will continue
based on load demand and the number of boilers connected to the BMS.
SYS INTLK CONFIG
This option selects when the System Start Interlock takes effect. The available choices are START
ENABLED (default) and ALWAYS ENABLED. If START ENABLED is selected, the BMS II will wait 30
seconds after the System Start Relay is activated before looking for a closure across the System Start
Interlock selected. (See SYS START INTLK in the RELAY MENU). If no closure is seen after 30
seconds, the BMS II will stop the boilers and display a fault message and activate the fault relay.
ALWAYS ENABLED will cause a fault whenever the interlocks are opened.
NOTE:
The BLR START LEVEL and BLR STOP LEVEL must be
programmed in the BMS II by the user. Refer to Appendix I for
additional information on START/STOP LEVELS.
BLR START LEVEL
The Boiler Start Level (BLR START LEVEL) sets the percentage level at which the Boilers connected to
the BMS II will start. The allowable entry range is from 1% to 100% (default = 20%).
BLR STOP LEVEL
The Boiler Stop Level (BLR STOP LEVEL) menu option set the percentage level below which the Boilers
connected to the BMS II will stop. The allowable entry range is from 1% to 40% (default = 16%).
MAX POWER INPUT
The Maximum Power Input (MAX POWER INPUT) sets the maximum Percent Level that the BMS II can
ramp up the boilers to. This may be useful in an over-sized boiler plant. The allowable entry range is
from 50 % to 100% (default = 100%).
FAIL SAFE MODE
Selects the desired operating mode of the BMS II if it loses its Outdoor Air Sensor when operating in the
Outdoor Reset mode, or loses its Remote Signal when operating in the Remote Setpoint mode. If
CONSTANT SETPT is selected as the FAIL SAFE MODE, the BMS II will operate the boilers to achieve a
Header Setpt equal to the programmed Internal Setpt. If SHUTDOWN is selected, it will shut down all the
boilers.
NOTE:
If the Header Sensor is lost, the BMS II will shut down all the boilers.