OPTIONAL FEATURES
HeatNet Control V3 3.x
Page 66
The amount of flow required for a boiler during the
pump post purge period is reduced to the minimum flow
rating of the boiler. This is meant to address the flow
faults the Member boiler was triggering when the
Master opened its valve during the Member’s pump post
purge time, reducing the flow. The system will need to
maintain a little more the twice the minimum flow of the
boilers to still be able to prove flow in post purge with 2
valves open.
We can also use the Local Delay time setting, located in
the DHW settings menu page 2, to require the boiler to
prove the required flow for a certain time period before
trying to fire. This value defaults to 5s but can be
increased up to 600s. The boiler will not prove flow,
and try to fire, until it sees the required flow present for
the delay time set in the Local Delay setting. Ideally
this value should be set to the stroke time of the valves
to assure all the valves are in their final position before
attempting to fire.
Figure 47
Local & DHW Pump connections
Local Pump/Valve
Normally Closed &
Normally Open Contacts
DHW
Normally Closed &
Normally Open Contacts
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
SETTINGS:
LOCAL PUMP: 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 jumper on the control board is in position 0-10 or 4-
20mA as required.
Combustion Air Damper
Relay K5 and the terminal J13 DAMPER is used to control a
combustion air damper. J12B.7 & .8 are used to detect the dry
contact proof switch from the damper. A proof time of up to 4
minutes can be set before the boiler can start or an alarm
condition will occur. The Combustion Damper can be setup in
the
SETTINGS: COMBUSTION AIR DAMPER
menu.
Using the LINKED/COMMON setting, the MASTER boiler
controls a system damper, so in the event this damper fails to
open, the system will not start. If the MASTER boiler’s
system damper fails, then no call for heat will be made to the
MEMBER boiler(s).
Using the INDEPENDENT setting, each MEMBER boiler
can control its own damper and is independent of the
MASTER boiler when a call for heat is made to the
MEMBER. This allows for separate dampers for each boiler.
They can be wired to J12B terminals 7 and 8.
If a common system damper is used (controlled by the
MASTER boiler), each individual boiler must prove that the
combustion air damper is open when it is placed in LOCAL.
This may be done using J12B terminal 7 on all boilers wired
to the damper’s prove switch. Terminal 7 is the sense input
and terminal 8 is 24 VAC. Connecting a wire to terminal 8 is
not recommended.
A separate/independent 24 VAC source is
recommended to be used for the damper prove
switch when a common system damper is used.
If you use terminal 8 to supply power from the
MASTER and the MASTER is powered OFF,
no boiler will be allowed to fire due to the loss
of power through the prove switch. A backup
boiler will also need to have the damper relay
contacts wired in parallel with the MASTER
for when the MASTER is powered OFF.
A second wire on the MASTER J12B terminal 7 is then
connected. The other end of this wire is then run to the first
MEMBER boiler J12B terminal 7. If another MEMBER
boiler is present, a second wire can be connected to the first
MEMBER boiler J12B terminal 7 and the other end
connected to the other boiler J12 terminal 7. This method can
be continued if additional boilers are present. This input must
be selected in the
SETTINGS: COMBUSTION AIR
DAMPER
menu.
Outdoor Reset
The Outdoor reset feature allows the water setpoint
temperature to change dynamically with the outside air
temperature. It also provides an adjustable temperature that
shuts the boiler (or boiler system) down when the outside
temperature rises above it.