Knight WH 399, Service Manual

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1
Service
24
Service Manual
BMS Thermostat Input
When controlling the boiler through the 0 - 10V BMS input
or through ModBus, the boiler can be enabled one of two
ways. With the
BMS Thermostat Input parameter set to
ACTIVE, the boiler will be enabled by closing the Heat/Loop
Demand 1 input. When set to INACTIVE, the boiler 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 boiler 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 Active / Inactive)
and the boiler is being controlled through ModBus, set the
ModBus parameter to ACTIVE. Otherwise, set the ModBus
parameter to INACTIVE. Note that the boiler can still be
monitored by ModBus with this parameter set to INACTIVE.
The default value is INACTIVE.
ModBus T/O
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 boiler designated as the Leader of the Cascade 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
boiler designated as the Leader. 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 boilers.
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 equal the demand, 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.
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 20 minutes. The limit value can be
set between 0% and 100%.
Ramp Settings
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 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.
Please note that the brackets ([]) denote
screen status.
NOTICE
Control modes
The United States Energy Policy and Conservation Act
requires residential heating boilers with inputs less than
300,000 Btu/hr be equipped with a control that automatically
adjusts boiler water temperature in relation to heat demand.
An external control may be connected to control the firing
rate or the set point of the boiler provided that either an
external energy management system is installed that reduces
the boiler water temperature as the heating load decreases,
the boiler is not used for any space heating, or the boiler is
part of a modular or multiple boiler system having a total
input of 300,000 Btu/hr or greater.
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. The inlet temperature control is only available
with a stand-alone 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.