Laars MASCOT LX, Service Manual

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65
Mascot LX Service Manual
Cascade Setup
B28
Up to eight Mascot LX units can be set up in a “cas-
cade.” To do this, the boilers must be “daisy-chained”
together using Modbus.
Modbus Wiring -
The Modbus terminals are located on the low-voltage
terminal strip: 17 = A, 18 = B, and 16 = ground. See Fig.
B28-1.
The quality of the wiring is important. The wiring should
be three-wire shielded cable with ground. The ground
wire should be connected to a good chassis ground at
one end of the daisy chain only . Wire terminal A on one
boiler to terminal A on the next, and so on.
Modbus Address Auto Configuration -
To configure the control system, identify which boiler is
going to be the “master” for the cascade. Go to Installer
mode. Go to parameter P06 - “Cascade Address.” Set
the address to “0”, and press and hold the OK/Select
button. When “Auto Cfg” appears on the display, press
OK/Select to start the auto configuration process. The
controller will find all of the boilers connected to the
system and assign Modbus addresses. When the auto
configuration is complete, the display will say “boilr #”,
where “#” is the number of boilers found on the cascade
system.
Modbus Address Manual Configuration -
The Modbus addresses may also be configured manu-
ally. Identify which boiler is going to be the “master” for
the cascade. On that boiler, go to Installer mode. Go to
parameter P06 - “Cascade Address.” Set the address to
“0.” Press OK/Select. (Do not press and hold OK/Select
- that would trigger the auto configuration routine.)
On each of the other boilers, set up the Modbus address.
Go to P06, set the address using a unique number, and
press OK/Select.
Setting Cascade Setpoints -
The setpoints must be set up on each of the boilers. On
each boiler, go to Installer mode. The three parameters
are:
P07
Cascade Setpoint
P08 Cascade Off Hysteresis
P09 Cascade On Hysteresis
Be sure that the value for P09 is always higher than the
value for P08.
Fig. B28-1 - Modbus Connections