25
P/N 42-9452 8/08 Copyright Hydrotherm
KN USER’S CONTROL MANUAL
Control menus and adjustments
(continued)
4
Menu item
Under . . .
Explanation
HEAT BAND
BOILERS
The heat band is the height of the modulating
band. When the water temperature is between ½
the heat band above or below the setpoint
temperature, boiler fi ring rate modulates. Boilers
are at minimum input at the upper end of the band
and maximum input at the lower end of the band.
Boilers come on only if the water temperature is
below the band. Boilers stage off when the water
temperature is above the band.
LOC SETPT
SETPOINTS
Setpoint temperature controlled by the KN control.
NOTE: If the control is operated by a Master control or by a remote control (building management
system, 4-20ma control, etc.), this setpoint temperature only comes into play when the KN-2
control is in override mode (such as by closing its Heat Demand or DHW Demand terminals).
SOURCE
SETPOINTS
Specifi es where the space heating setpoint temperature comes from:
AUTO means the KN control determines the setpoint (using local setpoint, outdoor reset or
header temperature setpoint).
The option is “4-20ma.” If 4-20 ma is selected, the KN control determines setpoint based on the
signal it receives at the 4-20ma terminals on the connection board. The setpoint temperature
(°F) equals the signal current (ma) divided by 0.09; example, a signal of 10ma will cause a
setpoint of 10/0.09 = 110°F.
DHW SETPT
SETPOINTS
This is the setpoint temperature for the boiler outlet water (or header water temperature) when
the DHW Demand terminals see a closed contact (DHW tank temperature control calls for heat,
for example).
OP LIMIT
SETPOINTS
This is the temperature at the boiler outlet (or header sensor) that will cause the control to shut
down on high temperature limit. It must be high enough above the upper end of the heat band
to avoid nuisance cycling.
The maximum setting is 205°F.
Example: If the boiler setpoint is 180°F, and the heat band is 30°F, the upper end of the heat
band is 180 + 30/2 = 195°F. The limit band (see below) must be set at 10°F so the OP LIMIT
setting can be: 195 + 10 = 205°F (maximum allowable setting).
The operating limit setting (OP LIMIT) always limits boiler outlet water temperature, regardless
of how the boiler is controlled (HeatNet member, 4-20ma control or stand-alone). The limit
band (see below) determines when the boiler begins to be forced to reduce input as the outlet
temperature rises toward the limit setting.
LIMIT BAND
SETPOINTS
If the boiler outlet water temperature rises toward
the limit setting (OP LIMIT, above), the KN control
will begin to reduce the boiler’s fi ring rate when
the temperature gets within the LIMIT BAND
degrees F below the operating limit setting. At
the lower end of the limit band, the boiler can fi re
up to maximum input (100%). By the time the
temperature reaches the upper end of the band
(the OP LIMIT setting), the boiler is limited to
minimum input (20%).
The limit band reduces the likelihood of short cycling on boilers controlled by a master control
or a remote control by reducing boiler maximum allowable fi ring rate as the temperature rises
toward the limit setting. Make sure the lower end of the limit band is above the upper end of the
heat band.
Table 8
Setup menus — parameter explanations
