OPTIONAL FEATURES
HeatNet Control V3
Page 61
System Pump connections
The summer pump jog is a special feature that can be selected
when the system is in summer shutdown (OUTDOOR
RESET). The jog allows the system circulator pump(s) and
the local pump to run for the system pump purge time once a
week. It can be set to any day of the week and will occur at
12:01 AM. If (2) system pumps are present, and after the first
pump finishes its post purge, the second one will start and the
first one will stop.
The system flow proving switch is implemented using
SPARE 3/System Water Flow on J11A. If a flow switch is
connected to the WTR FLW interlock, the HeatNet control
will wait up to 10 seconds to prove flow. 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.
When (2) system pumps are present and flow is not
established or is lost (2) things will occur to try and keep heat
in the system.
1.
When first starting a system:
If after a 10 second
wait to establish flow has failed, the first pump will
change to the second pump. The second pump will now
try to establish flow for 10 more seconds. If the second
pump fails to establish flow, the HeatNet control waits
10 minutes
. After the 10 minutes has expired, the
control now starts with the second pump and attempts
to prove flow for 10 more seconds. If flow does not
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 PUMP HOURS the
PUMP ROTATION will be temporarily set to
SYSTEM HOURS. This is to prevent re-starting the
failed pump due to its runtime hours. Setting the
PUMP ROTATION to SYSTEM HOURS 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.
System
Pump 1
System
Pump 2
K4
K13
System Flow
Prove Switch
