OPTIONAL FEATURES
HeatNet Control REV 1.38-1
Page 25
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 HeatNet Control 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 0-10VDC control signal on J4 pins 7+ and
4- to the modulation rate. (2) wires need to be run from J4.7+
and J4.4- to the VFD’s input connection
Auxiliary Functions
Relay K5 and the terminal J13 is used to control a combustion
air damper. The input J12B is 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
SETUP:AUX FUNCTIONS
menu.
The Master boiler controls the 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).
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
member 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 7on the 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.
See Figure 35,
Common System Damper Wiring
, Page 42.
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
Maste,r 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
SETUP:AUX FUNCTIONS:COMBUST 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/boiler system down when the outside
temperature rises above it.
Figure 23
Outdoor Reset Curve, Typical
The above chart shows how the water temperature setpoint
changes with the Outside air temperature. The four values of
180, 10 and 140, 70 are the default values:
WATER TEMP
LOW OA TEMP
180°F
10°F
Water temp @
outside air temp
WATER TEMP
HIGH OA TEMP
140°F
70°F
Water temp @
outside air temp
WWS Setpoint
72°F
Outside air temperature
where Warm Weather
Shutdown occurs
WARM WEATHER SD=ON
If set to ON here
The chart depicts what the water temperature setpoint will
equal with a corresponding outside air temperature. At an
outside temperature of 10F and below, the water temperature
setpoint will be limited to 180F. With an outdoor temperature
of 70F and above, the water temperature will be limited to
140F. The water temperature setpoint will track along the
charts plotted line with corresponding outside temperatures.
The OR OVR (Outdoor Reset Override) input on J12A can be
used to override this Outside Air Setpoint and maintain the
water setpoint at the LOCAL or SYSTEM SETPOINT value
