Lochinvar FTxl 500 Service Manual page 26

1
Service
Ramp Settings
Please note that the brackets ([]) denote
NOTICE
screen status.
The SMART SYSTEM control can be programmed to limit
the firing rate for a fixed period of time at the start of a space
heating or BMS set point demand. There are six (6) possible
limits, each with their own time delay. The first limit applies
as soon as the burner starts. Once its time delay expires, the
second limit is applied and its timer begins. The control steps
through these limits until the 6th (sixth) limit expires. Note,
however, that the 6th limit will also limit the rate for the rest of
that heat demand. The installer can adjust the firing limits and
time delays by accessing the Ramp Settings parameter. Once this
parameter is selected, the screen will show the step number, the
time delay for that step and the limit value corresponding with
that step. If the installer wishes to adjust one of the values in
that step, he can press the NAVIGATION dial until the value
he wishes to change is flashing. The installer can then rotate
the NAVIGATION dial to adjust that value. If the installer
presses the RIGHT SELECT [SAVE] key while the limit value
is flashing, the step value will flash again. The installer can
then select the next step and adjust the delay and limit values
corresponding with that step.
When finished, the installer can press the RIGHT SELECT
[SAVE] key to store the new settings, or the LEFT SELECT
[EXIT] key to return to the Anti-Cycling parameter list
without saving the changes. The delay value can be set between
0 minutes and 40 minutes. The limit value can be set between
0% and 100%.
Control modes
Controlling Sensor
The SH controlling sensor parameter selects the sensor the
control will use to regulate the boiler firing rate. This parameter
is adjustable by the installer by accessing the Controlling Sensor
parameter. The sensor selections are as follows: The outlet
sensor regulates the firing rate based on the outlet water
temperature of the boiler and the inlet sensor regulates the
firing rate based on the inlet water temperature of the boiler.
If the outlet sensor is selected, and the optional system supply
sensor is connected, the control will regulate the firing rate
based on the system supply sensor temperature. The default
sensor is the Outlet Sensor.
Cascade Address
The boiler designated as the Leader needs to be programmed
with address 0. All the Member boilers require addresses from
1 to 7, and the addresses must be different for each Member.
The addresses can be in any order, regardless of the order in
which the units are wired together. This parameter is adjustable
by the installer by accessing the Cascade Address parameter.
The outdoor air (if used) and system supply sensor must be
connected to the Leader boiler. The default address is 1.
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Service Manual
Maximum Cascade Set Point
This parameter determines the set point used by the individual
boilers in a Cascade when a system sensor is connected to the
Leader boiler. When a boiler is commanded to fire by the Leader
boiler, it will attempt to achieve this temperature at its outlet.
The Leader boiler will limit the modulation of the boiler(s) in
order to hold the temperature at the system supply sensor to
the user set point. If any of the boiler outlet temperatures reach
the maximum cascade set point, that boiler will then modulate
down on its own in order to keep its outlet temperature within
the maximum cascade set point. Therefore, this parameter can
be used to limit the outlet temperatures of all the boilers in a
Cascade. Note that this parameter does not apply when the
boiler is heating an indirect DHW tank programmed as normal.
This parameter is adjustable by the installer by accessing the
Maximum Cascade Set Point parameter. The temperature range
of this parameter is 32°F (0°C) to 190°F (88°C). The default
maximum cascade set point is 185°F (85°C).
Cascade Offset
This parameter determines how much the temperature must
go above set point before the lead boiler will turn off. This
parameter can be adjusted by the installer by accessing the
Cascade Offset parameter.
parameter is 0° to 20°F (11°C) The default value is 10°F (6°C).
Cascade Differential
This parameter determines how much the temperature must
go below the turn off temperature (Set point + Offset) before
the lead boiler turns on. This parameter can be adjusted by the
installer by accessing the Cascade Differential parameter. The
temperature range of this parameter is 0°F to 60°F (33°C) The
default value is 20°F (11°C).
Cascade Type (L/L / EFF)
There are two (2) options for the way a Cascade divides the
load between its heaters. The first is Lead/Lag, designated as
L/L in the menu. This method is used when it is desired to
have the least amount of total flow through the boilers. This
method will modulate the last two (2) boilers that are firing.
This provides for smooth transitions when a boiler turns on or
off. When the last boiler reaches 100% and the calculated load
is still increasing, it will start the next boiler at 20% and reduce
the previous boiler to 80%, thus eliminating the sudden jump
in total output of the Cascade. When the calculated load is
decreasing and the last boiler gets down to 20% fire, it will hold
it there and start lowering the firing rate on the next-to-last
boiler. When the next-to-last boiler reaches 20%, it will turn
the last boiler off and raise the rate of the next-to-last boiler to
40%, thus eliminating the sudden drop in total output of the
Cascade.
The other Cascade divider method is Efficiency Optimization,
designated as EFF in the menu. This method is used, as the
name implies, when it is desired to have the most efficient
system. When the first boiler reaches 100% rate, it lowers its
rate to 50% and turns on the next boiler at 50%. The two (2)
boilers then modulate at the same rate.
The temperature range of this