AERCO BMS II BOILER - Manual (Page 45)

OPERATION
3-13
DERIVATIVE GAIN
Derivative Gain is a function of time. It senses and responds to the rate of change of the setpoint error.
A slow rate of change will yield a small amount of derivative gain. Conversely, a fast rate of change will
yield a large derivative gain. Too high a derivative gain setting will produce a large output for a short time.
This can result in overshoot of the setpoint. Too low a derivative gain setting will have the opposite effect,
producing a small output for a longer period, and may result in slow system response or the system
undershooting the setpoint.
HDR TEMP DEADBND
This is the temperature deviation allowed from setpoint within which the Percent Level output will remain
constant. The default value is 5°F.
3.11 RELAY MENU
As the name implies, the RELAY MENU contains the options necessary to select the actions performed
by the System Start (SYS START), Fault Alarm (FLT ALARM) and Auxiliary (AUX) Relays in the BMS II.
SYS START TEMP
If an Outdoor Air Sensor is installed, this menu option is used to select the Outdoor Temperature below
which the System Start Relay is allowed to activate (close), provided that the SYS START OPTION
conditions specified below are satisfied. The percent level will always remain at 0% until the System Start
Relay is activated The System Start Relay will open if the Outdoor temperature is above the value set for
this option.
SYS START OPTION
The SYS START OPTION can be set to TEMP ONLY or TEMP AND LOAD. Selecting TEMP ONLY
means the System Start Relay will be active whenever the Outdoor Temperature falls below the System
Start Temperature (SYS START TEMP).
Selecting TEMP AND LOAD will cause the System Start Relay to activate if the Outdoor Temperature
falls below the System Start Temperature and the Percent of Load (Operating Menu) is at or above the
LOAD START PCT (Calibration Menu). It will deactivate (open) the System Start Relay when the Percent
of Load goes below the LOAD START PCT.
SYS START INTLK
The SYS START INTLK selects the Interlock associated with the System Start Relay activation when
SYS INTLK CONFIG is set for START ENABLED. Available settings include, INTERLOCK 1 (default),
INTERLOCK 2, or INTERLOCK 1&2.
AUX RELAY OPEN
The AUX RELAY OPEN setting is the Percent Level output below which the AUX Relay will open if it was
closed due to the conditions described by the AUX RELAY CLOSE setting.
AUX RELAY CLOSE
This determines the condition for which the AUX relay will close. If 100% FIRE RATE is selected, the
AUX relay will close when all available boilers are firing at 100%. If 100% AND OFF (default) is selected,
it will close when all available boilers are firing at 100% as well as when no boilers are available and the
boiler plant is below setpoint. This relay can trigger emergency heat in the latter case.