Lochinvar Knight 151, Руководство по обслуживанию, Страница: 16 / 40

16
1
Service
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
The ModBus T/O is 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
parameters. 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).
Outdoor Armor Water Heater Service Manual