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

SETTING THE TRIGGERS AND THE START /STOP TIME DELAYS FOR THE LEAD LAG SYSTEM
The value entered in this box will be subtracted from the setpoint to create
the boiler On point. This On point has two separate functions–
1)If the system has ON/OFF boilers, it will use the ON POINT as a trigger
to turn on the next boiler.
2)If the system is using modulating boilers only the lead boiler will use
the on point to turn on.
0% of firing rate =
low fire
100% of firing rate
= high fire
Input box. Firing rate of
the running boiler
which when reached
will start the timer to
start the next boiler in
sequence. The limits of
this value are between
50 and 100.
Input box. Firing
rate of the running
boiler which when
reached will start
the timer to stop the
last boiler in the
sequence. The
limits of this value
are 0 - 50.
Adjustable start time
delay which delays
the starting of the next
boiler in the sequence
once the start trigger
is made. The limits of
this value are 90-900.
Adjustable stop time
delay which delays
the stopping of the last
running boiler in the
sequence once the stop
trigger is made. The
limits of this value are
0-1200.
Figure 5.4: Lead Lag Trigger Setup Screen
The value entered in this
box will be added to the
setpoint to create the
boiler Off point. This
Offpoint has two separate
functions–
1)If the system has
ON/OFF boilers, it
will use the Off point
as a trigger to turn
off the last running
boiler.
2)If the system is using
modulating boilers
only the lead boiler
will use the the Off
point to turn off.
Example, using the values above (Modulating boilers) :
Boiler 1 is on and reaches 90% of firing rate. The firing rate
will have to stay above 90% for 120 sec for the next boiler
in the sequence to start. If it drops below 90% before the 120
second time delay is complete, the timer will reset.
Example (On/Off boilers) : Assume a setpoint of 180 °F.
The On and Off points are programmed on the screen at 5
and 5. Therefore the boilers will turn on a 175 °F and off at
185 °F. The boilers have a differential of 10°F.
Boiler 1 is on and the temp at the system water temperature
sensor drops below 175 °F for 120 sec., the next boiler in the
sequence will start. If the system water temperature rises to
175 °F before the time is complete, the timer will reset.
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