I&O Manual - ECCS Control System - Categories On Thermal ...

2.3.3. When a boiler becomes available again (fault
cleared, switch from local to remote, etc.) the system
will put it back in the sequence. If the desired lead
becomes available it will start immediately and may
shut down the last boiler running in the sequence
depending on how many boilers are required.( EX: In a
3 boiler system, if 2 boilers are running and only 2 are
required when the lead comes back in service it will
shut down the last lag boiler. If 2 are running and 3 are
required it will not shut down the last lag boiler.)
2.4 AUTO ROTATE
When this function is selected by pressing the Auto
Rotate button (refer to Figure 5.5) the sequence will
automatically rotate based on how long the lead boiler
runs. The rotation time will be set by the operator.
After rotation time is reached, the Lead boiler will move
to the end of the sequence and the second boiler will
become the lead.
When the rotation time is reached, the next boiler in the
sequence will start. After the unit is running for a few
minutes the sequence will rotate, dropping out the old
lead boiler. This will insure the same amount of boilers
are running before and after rotation occurs.
If the sequence is changed manually, the rotation timer
will start from the beginning.
2.5 OUTDOOR RESET
The outdoor reset function (refer to Figure 5.6)
generates a setpoint based on a curve programmed on
the screen and the outdoor air temperature. Two points
are entered and a linear curve is generated.
An RTD temperature sensor will send a signal to the
RTD module for the PLC.
If outdoor reset is enabled through a switch on the
screen, the setpoint will be generated by the curve for
outdoor reset programmed on the screen.
2.6 WARM WEATHER SHUTDOWN/ENABLE
DISABLE
The Warm Weather Shutdown (WWSD) (refer to
Figure 5.10) function will shutdown either the boilers,
the system pumps or both depending on the selections
on the WWSD screen. When the outdoor air
temperature goes above the temperature set in the high
outdoor air temperature box on the outdoor reset
screen, shutdown will occur.
The outputs for energizing a relay for controlling the
system pumps, O:0.0 and O:0.1 (Refer to figure 3.5) will
energize when the system goes into a WWSD
condition. This is a fail-safe condition. If power is lost
to the ECCS panel the pumps will still operate.
7
Once the OAT>HAT setting, a 60 sec timer starts. If the
condition is still true at the end of the 60 seconds the
WWSD function will energize. If both the boilers and
the pumps are selected to shut down, the boilers will
shut down first and 30 seconds later the system pumps
will shut down. This is done to minimize cycling around
the HAT, which triggers the WWSD function.
The WWSD function (or can be used as an Enable/
Disable signal for all boilers) can also be activated with
an external contact closure between terminals L+ and
I:0.1 (Refer to figure 3.5). Ensure that the WWSD
function is not enabled on the ECCS panel. This will
function only when the boilers are in the remote mode
and being controlled by the ECCS panel. If the boilers
are in the local mode they will not be shut down
by this function. There will be a 1 minute delay before
shutdown once the contact is closed.
2.7 MODBUS COMMUNICATION
The ECCS Panel uses the Modbus protocol to
communicate with all the boilers in the system. The
Flame Safeguard and the temperature controller both
have Modbus communication capability. Information
such as faults, alarms, flame signal, cycles, hours,
setpoint, and on/off points can all be communicated to
the touch screen.
2.8 TRENDING
System water temperature and outdoor air temperature
are trended for total of 8 hrs (refer to Figure 5.13). The
standard screen shows one hour of time and that trend
can be zoomed in or out from 7.5 minutes to 8 hours.
Points on trend are recorded every 30 seconds.
2.9 LOCAL/REMOTE OPERATION
A Local/Remote switch is located on the Boiler
Parameter screen on the touch screen (refer to Figure
5.7). Some boilers may have an optional physical
selector switch on the front of the boiler.
The Local/Remote selector switch enables the boilers
to be controlled from either the temperature sensor on
the individual boiler (Local) or controlled from the
System water temperature sensor (Remote). If the boiler
is in the remote mode, the display on the individual
boiler temperature control will flash Re F (Remote Firing
Rate) and the remote setpoint. If in the local mode, the
display will show the local setpoint without flashing.
*Fail-safe Operation*
If power is lost to the ECCS panel, the boilers will
automatically revert back to the local mode.