User Guide

16
1 Service
Anti-Cycling
Anti-Cycling Time
Once a DHW demand has been satisfied, a set amount of time
must elapse before the control will respond to a new DHW
demand. The control will block the new heat demand and anti-
cycling will be shown in the display until the time has elapsed
or the water temperature drops below the Anti-Cycling Override
Differential parameter. This parameter can be changed by the
installer by accessing the Anti-Cycling Time parameter. The time
range for this parameter is 1 minute to 10 minutes. The default
value is 1 minute.
Anti-Cycling Override Differential
The control will bypass the anti-cycling time if the inlet water
temperature drops too much. The control will use the inlet water
temperature at the time it shut off as the starting point. If the
inlet temperature drops below the temperature parameter the
control will abort anti-cycling and allow the water heater to fire.
This parameter can be changed by the installer by accessing the
Anti-Cycling Override Differential parameter. The temperature
range of this parameter is 0°F (0°C) to 54°F (30°C). The default
value is 10°F (6°C).
Control modes
BMS Thermostat Input
When controlling the water heater through the 0 - 10V BMS
input or through ModBus, the water heater can be enabled one
of two ways. With the BMS Thermostat Input parameter set to
ACTIVE, the water heater will be enabled by closing the tank
thermostat input. When set to INACTIVE, the water heater will
be enabled by the voltage level on the 0 - 10V input (in the case of
0 - 10V BMS control), or the 0 - 10V input value received through
ModBus. The default value is INACTIVE.
BMS
The set point or modulation of the water heater may be controlled
through the 0 - 10V BMS input or through ModBus. When the
BMS parameter is set to INACTIVE, the 0 - 10V input will be
ignored. When set to ACTIVE, the set point or modulation will
be controlled by the voltage on the 0 - 10V input (in the case of
0 - 10V BMS control), or the 0 - 10V input value received through
ModBus. The default value is INACTIVE.
ModBus
When BMS is set to ACTIVE (see BMS) and the water heater
is being controlled through ModBus, set ModBus parameter to
ACTIVE. Otherwise, set the ModBus parameter to INACTIVE.
Note that the water heater can still be monitored by ModBus
with this parameter set to INACTIVE. The default value is
INACTIVE.
ModBus T/O
This parameter determines the amount of time the unit controls
will wait to receive a communication string from the BMS
controller before reverting back to its own internal readings.
This parameter is adjustable by the installer by accessing
the ModBus T/O parameter. The adjustment range of this
parameter is 5 seconds to 2 minutes. The default value is
10 seconds.
Cascade Address
The water heater designated as the Leader needs to be
programmed with address 0. All the Member water
heaters 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
tank sensor must be connected to the Leader water heater.
The default address is 1.
Cascade Type
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 water heaters. This method will modulate the last two
(2) water heaters. This provides for smooth transitions
when a water heater turns on or off. When the last
water heater reaches 100% and the calculated load is still
increasing, it will start the next water heater at 20% and
reduce the previous water heater to 80%, thus eliminating
the sudden jump in total output of the Cascade. When the
calculated load is decreasing and the last water heater gets
down to 20% fire, it will hold it there and start lowering
the firing rate on the next-to-last water heater. When the
next-to-last water heater reaches 20%, it will turn the last
water heater off and raise the rate of the next-to-last water
heater 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 water
heater reaches a certain rate (default = 90%), it lowers its
rate to 45% and turns on the next water heater at 45%.
The two (2) water heaters then modulate at the same rate.
As the calculated load increases further and both water
heaters ramp up to 90%, it lowers the rate of the first two
(2) water heaters to 60% and brings the next water heater
on at 60%. The three (3) water heaters then modulate
together. As the calculated load decreases, the water
heaters will reach a lower threshold (default = 30%), at
which time the last water heater (the third in our example)
will turn off and the Cascade will increase the rates of the
remaining water heaters to provide the equivalent total
output as before ((3 x 30%) / 2 = 45% in our example).
Efficiency optimization is automatically selected when
heaters of different sizes are programmed into the Leader
water heataer (see Boiler Size on page 17).
Service Manual