OPTIONAL FEATURES
HeatNet Control V3 2.x
The BTU load value may also be accessed through Modbus
read registers 30242 (upper 16 bit word) & 30243 (lower 16
bit word). These two words will need to be combined in order
to get the BTU load value.
When using the BMS GPM register the BTU values are only
calculated to a whole GPM since the BMS GPM register
currently does not support floating point numbers.
The Building Management System (BMS) also has the ability
to limit the # of HeatNet boilers allowed to fire. When a
system has a fixed amount of boilers that HeatNet reports are
available, the BMS can limit the # of boilers that can fire. The
BMS can write the GPM value it has for flow, or directly
write a register with how many boilers HeatNet can control. If
the BMS GPM flow feature is active, the direct control
becomes inactive.
Note: using these features can limit HeatNet‟s ability to
maintain setpoint.
1.
Flow Limited Control
: This method helps HeatNet to
limit the # of boilers firing based on the System Flow in
GPM. In variable flow systems, this will limit HeatNet‟s
ability to add new boilers when insufficient flow is
available. The # of boilers allowed to fire is determined
by:
# of HeatNet boilers that can fire = BMS GPM Set Rate/
LOWEST FLOW
To activate this flow limited feature for use with a BMS:
b.
Set SETTINGS: FLOW METER: ENSBLED? YES
c.
Set ADVANCED SETTINGS: FLOW METER:
GLYCOL MIX ? % , Currently, any mix over 10%
de-rates the flow by 30% (rule of thumb method).
Example: if the LOWEST FLOW = 50 GPM, HeatNet
will calculate a New Lowest Flow required to be 65
GPM. The LOWEST FLOW does not need to be
changed, but is calculated to 65 GPM and that value is
used by HeatNet.
d.
Set SETTINGS: FLOW METER: INPUT TYPE to
BMS.
e.
Set SETTINGS: FLOW METER: LOWEST FLOW
(The automatic value loaded will equal the lowest
flow required for this boiler (it is adjustable). It should
be = to the lowest flow of the largest boiler in the
system).The HIGHEST FLOW & FLOW FACTOR
are currently not used with this release. Once flow
meter manufacturers have been determined, new
firmware will become available.
f.
Write to address BMS GPM register 40019 with a
valid flow (0 -1500 GPM).
g.
If a new GPM value is not written within 10
minutes, this feature will be deactivated until a
new flow value is written. Ensure periodic updates
of the flow register are done within 10 minute
intervals.
h.
To check if HeatNet is in a flow limited state, read the
boiler status 4 register starting at address 30160 for
the Master Boiler; if Status 4 bit (12) is set, it
indicates that the HeatNet control is running with
limited boilers due to insufficient flow derived from
the GPM value.
2.
Boilers Limited Control
: This feature allows the BMS
to directly change the amount of boilers that HeatNet can
control.
To Activate the Boiler limited feature:
a.
Read Modbus address 30241 to see how many
boilers HeatNet has available to fire. MODBUS
AVAILABLE BOILERS register.
b.
Determine how many boilers the BMS system will
require.
c.
Write to address BMS LIMIT BOILERS register
40020 with the # of boilers HeatNet is allowed to
control (0 - 16).
d.
If a new boiler # value is not written within 10
minutes, this feature will be deactivated until a
new boiler # is written. Ensure periodic updates
of the flow register are done within 10 minute
intervals.
e.
To check if HeatNet is in a BMS limited state, read
the boiler status 4 register starting at address 30160
for the Master Boiler; if Status 4 bit (13) is set, it
indicates that the HeatNet control is running with
limited boilers due to the BMS system specifying
BMS LIMIT BOILERS being less than the available
boilers.
3.
Flow Meter
: Used to control the # of HeatNet boilers
allowed to fire. HeatNet will look at the # of boilers it has
available, and the amount of system flow to determine how
many of boilers it can fire.
As an Example:
An Onicon F-
1210 Flow Meter provides simultaneous 0-10V and 4-
20mA outputs, so if the BMS system is using (1) output, the
other may be used by HeatNet.
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Summary of Contents for KN-10
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