Operating Modes - Navien NCB-24LDWE Installation & Operation Manual

2.6 Operating Modes

2.6.1 Operating in Space Heating Mode
To operate the Space heating mode, press the Space heating
button on the front panel and select a heating temperature
setpoint higher than current heating temperature.
1. When the boiler detects a request for heating production
(from the installation's room thermostat, for example), the
3-way valve goes to heating position and the circulating
pump starts up.
2. If the boiler water temperature is lower than the desired
temperature setpoint, the boiler ignites and heats up the
heating installation until the selected boiler temperature
is reached. The boiler's electronic control modulates
the burner output to adapt to the installation's heat
requirements at all times and so that the installation's water
temperature remains constant. This prevents the installation
from overheating and reduces heat loss as much as possible.
3. When there is no further heating demand (e.g. when
the desired ambient temperature selected on the room
thermostat is reached), the burner is extinguished (if it was
ignited) and the circulation pump continues to run during
the post-circulation time (minimum 3 minutes), to protect
the boiler from overheating due to thermal inertia in the
installation.
Blow Fan
Three
-way
Valve
Gas
Valve
Gas
Inlet
Flow
Out
16 About the Boiler
Exhaust
Gas
Air In Air In
Ignitor
Heat
Exchanger
Circulation
Pump
DHW Heat
Exchanger
CH
Return
2.6.2 Operating According to Outdoor
Temperature Conditions
The Outdoor Reset Control feature may be used to enhance
energy efficiency while maintaining optimal heating
performance. With the Outdoor Reset Control, the space heating
temperature setting automatically changes according to the
outdoor temperature and the current space heating system
application (system load).
You can configure the Outdoor Reset Control settings on the
front panel by entering the Special Parameter Setting mode.
Refer to "10.5 Setting the Parameters" on page 43.
The Outdoor Reset Control feature requires
Note
installation of an outdoor temperature sensor, and it
only works when the boiler is running in the normal
operation mode. It does not work when the boiler is
running in either the Minimum (MIN) or Maximum
(MAX) mode, or when the boiler's front panel displays
a fault.
Outdoor
High MIN
Absolute
MAX
Absolute
MIN
°F 113 104 95 86 77 68 59 50 41
°C 45 40 35 30 25 20 15 10 5
Space Heating Temperature Setting for the
Outdoor Reset Control Feature
The following tables list the default space heating temperature
range by system heat load and the applicable outdoor
temperature ranges.
To connect the outdoor temperature sensor to the
Note
boiler, carefully follow the connection instructions
provided in the "12.5 Outdoor Temperature Sensor
(Optional)" on page 66.
Outdoor
Low MIN
°F °C
194 90
185 85
176 80
167 75
High Mass Radiant
158 70
Low Mass Radiant
149 65
140 60 Cast Iron Baseboard
131 55
Custom
122 50
Radiator
113 45
104 40
Finned Tube Baseboard
95 35
Fan Coil
86 30
77 25
68 20
59 15
50 10
32 23 14 5 -4 -13
0 -5 -10 -15 -20 -25