AERCO BMS 168 - Manual (Page 9)

Section 2 ______________________________
Features of
the BMS____
A
PPLICATION
F
LEXIBILITY
Three different system or control options
can be selected at setup to match the needs
of any closed-loop system - Indoor/Outdoor
Reset, 4-to-20 mA Remote Setpoint, and
Constant Setpoint.
C
ONTINUOUS
C
OMMUNICATIONS
The BMS continually sends information to
the boilers and receives information from
them, providing total control of boiler plant
dynamics.
E
XCEPTIONAL
A
CCURACY
The BMS control system uses a PID
(Proportional Integral Derivative) control
algorithm to respond dynamically to system
changes. Water temperatures are precisely
controlled by modulating energy in put. A
supply water temperature of ±2°F is
assured.
B
UILDING
I
NDOOR
A
IR
T
EMPERATURE
I
NPUTS
The BMS accepts building indoor air
temperatures directly from a thermistor
sensor or from a 4-to-20 mA signal.
Adjustments can be made to the header
setpoint temperature to compensate for
varying building temperatures and
conditions.
S
EQUENTIAL
O
R
P
ARALLEL
O
PERATION
Modules can be either sequenced on, or run
in parallel, by selection from the front panel.
In sequential mode, boilers are brought on
one at a time, so turn-down ratio is 14
multiplied by the number of KC Series
boilers, or 20 multiplied by the number of
Benchmark boilers. This provides higher
energy savings and seasonal efficiency. In
parallel mode, all of the boilers are
modulated together at the same firing rate.
The turn-down ratio of the system is fixed at
14:1 for the KC Series boilers and 20:1 for
the Benchmark boilers.
B
UMPLESS
T
RANSFER
When in sequential mode, the BMS stages
boilers on and off, one at a time, at
selectable percentages of firing rate. The
result is a seamless transition and
undetectable room temperature changes.
Sequential mode has several other unique
features:
Run-Time Equalization : The BMS se-
quences boilers on a first on-first off basis,
which automatically equalizes the run time
of all boilers in the plant.
Automatic Load Distribution : The BMS
continuously monitors the number of
modules that are available for operation. In
the event of a boiler malfunction or when
service is performed, the BMS automatically
compensates for a lack of response from
any unit and brings on the next available
boiler to satisfy demand. This feature
operates in both parallel and sequential
modes.
2-1