Lochinvar FTxl 500 Service Manual page 27

1
Service
(continued)
As the calculated load increases further and both boilers
ramp up to 100%, it lowers the rate of the first two (2)
boilers to 67% and brings the next boiler on at 67%. The
three (3) boilers then modulate together. As the calculated
load decreases, the boilers will reach 20%, at which time the
last boiler (the third in our example) will turn off and the
Cascade will increase the rates of the remaining boilers to
provide the equivalent total output as before ((3 x 20%) / 2
= 30% in our example).
Efficiency optimization is automatically selected when
boilers of different sizes are programmed into the Leader
control (see Boiler Size on page 27).
Minimum On/Off Time
In order to prevent units in a Cascade from short cycling,
this parameter defines the minimum ON and OFF time for
each unit. The installer can adjust this time by accessing
the Minimum On/Off Time parameter. The minimum
setting is 0 seconds and the maximum setting is 10 minutes.
The default is 30 seconds.
Minimum Next On Time
In order to reduce the risk of temperature overshoot with
a Cascade, this parameter defines the minimum time delay
from starting one unit until the next unit may be started.
The installer can adjust this time delay by accessing the
Minimum Next On Time parameter. The minimum setting
is 0 minutes and the maximum setting is 10 minutes. The
default is 60 seconds.
Minimum Number of Pumps On
When the boiler is a Cascade Leader, it can force a
minimum number of boiler pump outputs to be on
continuously, regardless of how many boilers are firing.
This is normally used when the boilers are piped in a
full-flow configuration, and the boiler pump outputs are
controlling isolation valves. The Leader will force the
boiler pump output on the highest priority boiler to turn
on first, then the boiler pump output on the second highest
priority boiler, and so forth, until the minimum number of
pump outputs are turned on. The range of this parameter
is 0 to 8. The default value is 0.
Service Manual
Alternate Leader
This parameter allows the Member 1 boiler to automatically
assume control of the Cascade should it lose communication
with the Leader boiler. When programmed to YES, it is
recommended that the Member 1 boiler have its own set of
external sensors installed (such as the system supply sensor),
to maintain the same level of temperature control as with the
Leader boiler. Voltage signals (such as the 0 - 10V system
pump speed input) can be connected to both boilers.
DO NOT connect the sensors connected to
WARNING
the Leader boiler to the Member 1 boiler.
The actual water temperatures will be higher
than expected, which could lead to property
damage, personal injury, or death.
When communication is re-established with the Leader boiler,
Member 1 will automatically relinquish control of the Cascade
to the Leader boiler.
The default value of this parameter is NO.
Boiler Size
When boilers of different sizes are connected together in a
Cascade, the Leader boiler has to know the size of each boiler
in that Cascade. The Boiler Size parameters allow the installer
to program the size based on the Cascade address. This screen
shows the Cascade address and the size of the boiler with that
address (in kBtu/hr):
1. When the Boiler Size screen is first accessed, Cascade
Address (SELF) is shown.
2. Press the NAVIGATION dial twice to access the
Input setting. Rotate the NAVIGATION dial to increase the
boiler input. Input settings 0 - 400 kBtu/hr can be adjusted
in increments of 5 (5000 Btu/hr).
approximate boiler size is shown, press the RIGHT SELECT
[SAVE] key.
3. Rotate the NAVIGATION dial to select the address of the
next boiler in the Cascade. Repeat Step 2.
4. Once the size of the last boiler in the Cascade has been
entered and saved, press the LEFT SELECT [EXIT] key to
return to the Control Modes menu.
5. If no other parameters are to be adjusted, press the RIGHT
SELECT [HOME] key to save the new settings and return
to the Status screens.
The SMART SYSTEM control automatically uses the Efficiency
Optimization Cascade type when controlling boilers of different
sizes.
If the Leader boiler is controlling larger boilers (e.g., Copper-
fin II), those members will send their sizes to the Leader boiler
automatically. Do not program those sizes into the Leader
boiler.
When the closest
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