OPTIONAL FEATURES
HeatNet Control REV 1.38-1
Page 24
in this example 4.00mA. This hysteresis value is not
adjustable.
When using the 4-20mA setpoint control, a band may be set at
which the 4-20mA signal will operate over. The lower
setpoint is defined as 4mA SETPOINT and the upper setpoint
is defined as 20mA SETPOINT. The 4mA SETPOINT is
linked to the BOILER START x.xxmA where this starting
current is the lower setpoint. So if the 4mA SETPOINT is set
to 130F and the 20mA SETPOINT is set at 180F the band will
be established. Once a starting control current of BOILER
START 4.1mA is applied, and the 4-20 REMOTE ENABLE
INPUT is closed, the boiler will start and the setpoint will be
set to 130F. If a control current of 10mA is applied, the boiler
will track on a linear slope towards the 20mA SETPOINT
settling at a SETPOINT of ~149F. As the current increases to
20mA, the SETPOINT will indicate 180F. The Default setting
is 4mA SETPOINT: 50F, and 20ma SETPOINT 220F.
Anytime a new firmware version is uploaded to
the control, these values return to these
defaults.
If using the direct modulation mode by applying a 4-20mA
current, only the BOILER START x.xx setting applies.
The 4-20 mA input can also be set to HIGH PRIORITY. This
can be set in menu:
ADVANCED SETUP:4-20mA INPUT
.
This allows a member boiler to be taken offline and directly
modulated by an external control. If the Master is using it for
heating and the 4-20mA is set to HIGH PRIORITY, an
external control can now output a 4-20mA signal which will
take over the boiler’s fire rate. This is typically used for DHW
control.
Circulator Pump Options
The control has provisions for a system pump and a local
pump/valve. This is to allow for primary/secondary loop
configurations. The system circulator pump is implemented
using the K4 relay and normally open contacts at J13
marked SYSTEM PUMP.
The pumps require motor contactors to isolate
the on-board relay contacts. The on-board
relays should never be used to energize pumps
directly.
Figure 22
Pump Connections
Operator
System Pump
Combustion Air Damper
Local Pump/Valve
Alarm
DHW Pump/Valve
The
System Circulator Pump
is supported by (2) modes and
a special feature.
1.
The first mode will allow the circulator pump to remain
on, unless the control’s outside high air temperature
setting has been met when using OUTDOOR AIR
RESET.
2.
The second mode will allow the circulator pump to be
turned on whenever there is a call for heat (any control
input). This mode will stop the circulator pump when the
call for heat is lost and the pump post purge time has
been satisfied.
The summer pump jog is a special feature that can be
selected when the system is in Warm Weather Shutdown
(OUTDOOR RESET). The jog allows the system circulator
pump to run for the pump purge time once a week. It can be
set to any day of the week and will occur at 12:01 AM.
The system flow proving switch is implemented using
System Water Flow on J5B. If a local flow switch is
connected to the WTR FLW LOCAL interlock, the HeatNet
control will wait up to 240 seconds to prove flow. This time
is adjustable under
SETUP:PUMP OPTIONS
. The default
flow proving time is 10 seconds. It can be increased to allow
slower valves to open before flow is established. If flow is
interrupted after it has been established, an error will be
displayed and the boiler will cycle OFF. As long as there is
a call for heat, every 10 minutes the circulator pump will try
to re-establish flow and start the boiler again.
The
Local Circulator Pump
is supported by (3) modes and
(2) features.
1. The first mode allows the circulator pump to remain
on, unless the control’s outside high air temperature
setting has been met when using Warm Weather
Shutdown.
2. The second mode will allow the circulator pump to be
turned on whenever there is a call for heat (any control
input). This mode will stop the circulator pump when
the call for heat is lost and the pump post purge time
has been satisfied.
3.
The third mode works much the same as mode 2, but it
allows the inlet sensor (RETURN) to be used with the
outlet sensor (SUPPLY) to keep the pump on until a
delta (difference) temperature is met. A return
temperature sensor is required for this mode, because
the delta temperature (SUPPLY – RETURN) measured
is across the boiler. In this mode, the post purge time is
also used. After the delta temp has been met, the post
purge time needs to expire before the pump is turned
off. This mode works much the same as mode 2.
PUMP/VALVE OPTION
: This is a special feature of the
local circulator pump to prevent deadheading water flow
when all boilers are off. When this feature is enabled, the
master boiler will enable its local circulator pump/valve
when
NO
boilers are running. If boilers are running in
LOCAL override and not controlled by H-NET, but are
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