OPTIONAL FEATURES
HeatNet Control V3 2.x
Page 31
prove, the control changes to the first pump and
attempts to prove flow. This cycle will continue
indefinitely until flow is established.
If flow is lost
while running:
this process is also used in an attempt
to re-establish flow.
2.
If PUMP ROTATION is set to PMP HRS the PUMP
ROTATION will be temporarily set to SYS HRS. This
is to prevent re-starting the failed pump due to its
runtime hours. Setting the PUMP ROTATION to SYS
HRS will allow a retry of the failed pump after the
rotation hours has expired. Power cycling of the boiler
or using the PUMP ROTATION menu will revert back
to PUMP ROTATION = PMP HRS if this was the
original setting.
For
system pump modulation
a 0-10Vdc control signal
output is provided at J4.3 (signal) and J4.7 (ground). This
signal is output by the Master boiler as a percent function of
the number of boilers running and can be used to set the speed
of a System Pump using a Variable Frequency Drive. Two
wires are required and need to be inserted into the J4.3 and
J4.7 positions to access this signal.
Note:
This signal has a step response and is not linear to the
system or boiler‘s input firing rate.
The output signal is proportionally mapped to % using the
equation:
%VFD = (boilers running/total boilers)
The %VFD represents the stepped percentage of boilers
running where:
0Vdc = 0% (to) 10Vdc = 100%
If there are (6) boilers in a system and (2) are running, the
control signal = 33% or 3.3Vdc. This signal could then be
applied to a system pump‘s VFD to control the speed of the
pump relative to how many boilers are firing. The VFD would
need to be set appropriately to allow the correct flow through
each boiler.
In low volume systems sudden temperature changes may
occur when the flow is stepped up or down by a large
percentage. In these situations the ADAPTIVE MOD may
need to be disabled and the ORIGINAL KN method used.
Other adjustments may also be required.
Currently, no failsafe mode is available in the event the
Master boiler‘s control fails. If this method is employed, a
failsafe boiler could be used to override the control signal and
enable the system pump‘s VFD using some external wiring
and an external relay, or have the VFD default to a safe speed
on loss of the control signal.
If (2) pumps are available, pump rotation is available. The
rotation of the (2) pumps can be controlled using two
methods.
3.
Pumps are switched based on the system run time
4.
Pumps are switched by the difference between each
pump‘s runtime. The HeatNet control keeps a
running record of each pump‘s runtime in hours. If
a pump is taken offline or replaced. The runtimes
can then be adjusted until they become equal.
These features may be selected in the menu, SETUP:PUMP
OPTIONS:SYSTEM PUMP:PUMP ROTATION
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 visible to H-
NET, the pump(s) on these boilers are presumed ON. In this
situation, the master
will not
enable its circulator pump/valve
unless it is running.
Another feature of the PUMP/VALVE OPTION is to control
a local (primary) pump using a Variable Frequency Drive.
This feature may be required when a secondary system pump
is also variable speed. To enable this feature
: SETUP:PUMP
OPTIONS:LOCAL PUMP PUMP/VALVE
OPTION:LOCAL PUMP VFD: ON
. Setting this Option to
ON will map the control signal on J4 pins 1+ and 5- to the
modulation rate. (2) wires need to be run from J4.1+ and J4.5-
to the VFD‘s input connection. Ensure that the JS1 shunt
