SETUP & OPERATION HeatNet Control V3
Page 13
Flow” timer (adjustable 10–240 sec.). The flow switch
contact is checked on terminals J11B, 5 &6.
5. With all the interlocks closed, the boiler start relay K1
is enabled and energizes terminal 6 on the ignition
control. This signal is present on J5 Boiler Start
Operator. The control now displays “Waiting for Start
Sequence”
6. The ignition control begins its cycle and provides an
output signal from terminal 4 to the H-Net control J5
Blower. The H-Net control responds and provides an
output signal to the VFD which sets the blower to the
programmed pre-purge speed. If an Ametek blower is
used, a soft start speed is applied before the pre-purge
speed.
7. After air-flow is established the ignition control waits
for the air switch to close. When the air switch closes it
provides an input to terminal 7 and pre-purge timing
commences. The H-Net display indicates “Pre-Purge”.
8. When purge is complete the ignition control energizes
the pilot gas valve from terminal 8, and the spark
generator from terminal 10, beginning a 10-second Pilot
Flame Establishing Period (PFEP). The H-Net control
responds to J5 Pilot Valve and provides an output
signal to the VFD which sets the blower to the
programmed ignition speed. The H-Net display
indicates “Pilot”.
9. At the end of the PFEP the spark generator is de-
energized. If the pilot flame is detected, by the UV
scanner, the ignition control energizes the main gas
valve from terminal 9 to J5 Main Valve. The H-Net
display indicates “Running 0%” (0% indicates PID
modulation signal is not being calculated yet).
10. If main-flame is detected the H-Net control holds the
burner at the low-fire rate for the MODULATION
DELAY time period. After this timer expires, the PID
allows the boiler to modulate and places the boiler into
the running state.
As boilers are added to the system settings in the
SETTINGS: ADAPTIVE MODULATION MOD: DROP
DOWN menu determines when the modulation rate drops
down to compensate for the newly added BTUs. For the
drop down to be active, one boiler needs to be running when
a new boiler is added (see: Introduction: The FLEXCORE
CK-SERIES H-Net Control: Master).
If all boilers are firing, the modulation rate is released to go
to 100%. If all boilers are not firing, the modulation is
limited to the MOD-MAX clamp value. The MOD-MAX
clamp is used to keep the boilers running as efficiently as
possible. The following Mixed Boiler System Operation:
Selecting Mixed Boilers section outlines this with examples.
NOTE: If the boiler is running as a stand-alone boiler or
is direct modulated (including the AA input),
the MOD-MAX clamp will also be in effect for
the ADD BOILER DELAY time. This is to
minimize thermal shock to the boiler.
Once the header water temperature is in the heating band,
only the modulation rate is used to achieve the target
setpoint. The system will maintain the setpoint until the load
demand increases or decreases.
As the load decreases, the header water temperature will
start approaching the top of the band. The PID now lowers
the modulation rate to the boilers, attempting to keep the
temperature within the heating band. If the system is
delivering too many BTUs, the water temperature will cross
the top of the heating band.
When the header water temperature first exceeds the top of
the heating band, the boilers are again checked for the one
with the most runtime. The selected boiler will turn off
immediately and a shed boiler delay timer will be loaded
with the delay time. This time will need to expire before the
next boiler will be stopped, but only if the header water
temperature remains above the heating band. This timer is
used to allow the header water temperature to return back
into the band when a boiler is stopped. When a boiler is
stopped there is a fixed rate of BTUs (Min Fire) that will be
removed (PID discontinuity to modulate from Min Fire to 0
BTUs on a boiler). The timer allows for this loss of BTUs.
This cycle will continue until the call for heat is satisfied or
the Warm Weather Shutdown feature is enabled.
Mixed Boiler Types Using
Priority Sets
Using the Basic Multi Boiler System Operation, a MIXED
boiler Priority method may be added to control condensing,
non-condensing, base load, or other boiler SETs in a system
together. These sets compose a system which provides for
optimal performance and economy. Having dedicated sets
of boilers gives the system engineer a tool to create many
different boiler systems.
A boiler set can be constructed by simply setting the firing
Priority on each boiler (to be in a set) at the same priority.
Setting all (example) condensing boilers to the highest
Priority of 1, and then setting all (example) non-condensing
boilers to a Priority of 2, will create (2) sets of boilers, one
condensing and the other non-condensing. Once this is
done, the Priority 1 set of condensing boilers will have a
firing order that has a higher Priority and is independent of
the other non-condensing set with the lower priority. The
boiler set with the highest Priority can then be fired based
on a conditional settings menu. The lower Priority set will
follow.
To Next Page
Loading...
Need help?
General