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P/N HN-IOM-1 82-0331 Copyright 2009 Mestek, Inc.
Finned copper tube gas boilers & water heaters – Control manual
RBI
Futera
III
/XLF/FUSION
-Series boilers — HeatNet
TM
control
Control overview
The HeatNet control monitors boiler temperature and limit circuit inputs, modulating boiler firing rate
to meet demand. The control uses microprocessor electronics, watching time-average response from the
system to anticipate how much heat the system needs. Coupled with the five-to-one turndown of the boil-
er, this results in maximum operating efficiency. The boiler will provide unmatched seasonal efficiency.
The HeatNet platform
HeatNet controls are designed to provide an integrated boiler management system on every boiler. The
platform provides multiple levels of selectivity. HeatNet electronics can be operated as a simple single-
boiler control, while still providing intelligent regulation of boiler firing rate to match system demand.
With a few key strokes on the key pad, the HeatNet control can operate as a sophisticated multiple-boil-
er controller, using simple RJ45 cable interfacing between units. The control can even accept external
control commands from building managements systems (Modbus standard, with optional bridge for
BACnet or LonWorks) or 20-milliamp analog input from an external controller.
The control method used by the HeatNet control is based on digital communications, which eliminates
the need for analog control signals. Analog signal inputs are supported, but a higher level of control preci-
sion, repeatability and feedback is gained with digital communications.
The HeatNet control can be versatile, providing for operation in multiple ways:
As a stand-alone boiler, either modulating, two-stage or ON/OFF.
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As a boiler in a boiler network, using the on-board HeatNet protocol.
•
As a member boiler in a boiler management system (either directly managed by BMS or managed by
•
a MASTER HeatNet boiler that communicates with the BMS).
As a member of a remotely-controlled boiler network (4 – 20-milliamp regulation).
•
Setpoint can be determined by the HeatNet control or by a 4 – 20-milliamp input signal.
•
Network boilers can be operated by override commands for increased versatility.
•
This manual is arranged so the instructions for each of the methods above is self-contained. See the Table
of contents for selection and location.
PID response
The HeatNet control uses proportional-integral-derivative calculations to determine the response to
boiler water temperature changes. This means it not only looks at how far away the water temperature is
from the setpoint temperature, but how fast the temperature is changing and how it has responded over
time. This ensures the boiler won’t make sudden unnecessary changes in firing rate.
External limit monitoring & annunciation
In addition to controlling the boiler, the HeatNet control monitors external limits wired into the limit cir-
cuit connections. The control shuts down the boiler if a limit opens, and the digital display shows which
limit failed. Monitored limits include high limit aquastat, low water cutoff, flow, ignition control fault, gas
valve alarm and other optional or user-selectable limits.
Multiple boiler operation
The HeatNet control easily interfaces with other HeatNet controls. Multiple boiler operation using Heat-
Net protocol only requires RJ45 cables daisy-chained from boiler to boiler and a few key strokes setting
up control behavior. The master boiler is automatically selected by connecting a sensor lead to its SYS-
TEM HEADER sensor terminals. The HeatNet control recognizes the sensor and configures the boiler
as the master. Other boilers only need to have an address assigned.
Among the advanced design features of the HeatNet control is the MOD-MAX setting. This limits the
firing rate of all boilers to a pre-set maximum (70% by default). This means all of the boilers will be run
at a very efficient level until all boilers are on. Only then can firing rate increase above this setting. Boiler
rotation can be first-on/first-off, first-on/last-off, or true rotation (the HeatNet control monitors the total
on time of all boilers, and rotates their usage so the total on time is the same for all).
Futera
HeatNet
Electrical enclosure
