Install Instructions

70
11 Operating information
DHW Priority (Boiler)
The Smart System control allows the connection of a DHW
thermostat or tank sensor to the low voltage board. When
a tank sensor is connected, the DHW thermostat input is
ignored. The control will attempt to satisfy a DHW call
before a concurrent space heating call; however, the unit will
switch between SH and DHW calls according to the settings
SH/DHW SW Time and DHW/SH SW Time.
Anti-cycling
After the burner turns off, the control will delay the next
burner cycle for a set time period. The time delay will be
bypassed if the inlet water temperature drops too far during
the delay. On Combi only models, the anti-cycling delay does
not apply to DHW calls for heat.
Modulation
The Noble Fire Tube is capable of modulating its firing
rate from a minimum of 10% to a maximum of 100%. The
firing rate is dictated by the call for heat (i.e., space heating
or domestic hot water), the heating load, and various other
temperature limitations.
Boiler outlet temperature sensor
The Noble Fire Tube is factory equipped with a boiler outlet
temperature sensor which is also used as the limit sensor
for the heater. During a space heat call for heat, the outlet
temperature sensor is used to control modulation of the
boiler unless a system supply sensor is field installed.
System supply temperature sensor
A factory supplied, but field installed system supply
temperature sensor may be used with the Noble Fire Tube.
When installed, this sensor is used to control modulation of
the boiler during a space heat call for heating.
Boiler inlet temperature sensor
The Noble Fire Tube is factory equipped with a boiler inlet
temperature sensor.
Combi DHW outlet temperature sensor (Combi
Only)
The Noble Fire Tube is factory equipped with a combi DHW
outlet temperature sensor. This sensor is used to control
modulation of the boiler during a DHW call for heat. When
this sensor is missing, limited operation in DHW Mode is
possible by controlling the boiler outlet temperature to the
DHW set point.
DHW flow switch (Combi Only)
The Noble Fire Tube is factory equipped with a DHW flow
switch connected to the control that detects the presence of
DHW water flow rates greater than 0.32 gpm. This input tells
the boiler to provide heat for DHW heating.
Combi diverter valve (Combi Only)
The Noble Fire Tube is factory equipped with a diverter valve
used to route boiler water to the heating system when in the
Space Heating Mode or through the brazed plate heat exchanger
when in DHW Mode. This diverter valve is normally in the
DHW position, thus isolating the boiler from flow in the
heating system.
Boiler pump control (Combi Only)
The Noble Fire Tube is factory shipped with an internal boiler
pump used to generate flow for both space heating and DHW
operation. The boiler pump will run whenever the burner is
firing. The boiler pump will also run during Combi Pre-Heat
Mode. The boiler pump will continue to run for a short time
after the burner turns off, or the Combi Pre-Heat Mode ends.
System pump control (Combi Only)
The Noble Fire Tube is capable of controlling a field supplied
and installed space heating system pump. The system pump
will run whenever there is a space heating call for heat. The
system pump will continue to run for a short time after the end
of the heat demand.
Boiler and system pump control (Boiler Only)
The boiler pump will run whenever the burner is firing, unless
the DHW is programmed for Normal Mode and the boiler is
heating the DHW tank. It will continue to run for a short time
after the burner turns off.
The system pump will run whenever there is a space heating
call for heat demand. It may be programmed to run during a
DHW call for heat when the DHW is programmed for Zone
Mode. It will continue to run for a short time after the end of
the heat demand. The system pump can be programmed to run
continuously if desired, except during outdoor shutdown and/
or a DHW call for heat.
A boiler pump is NOT supplied on boiler only models. On
boiler only models the boiler pump generates flow only for
space heating.
Gradient limiting
If during operation of the boiler the outlet water temperature is
rising too quickly, the control will reduce the firing rate to its
lowest setting.
SH rate limiting
The Noble Fire Tube includes an SH Rate Limiting feature that
limits the maximum modulation during a space heating call.
Installation & Service Manual
FIRE TUBE
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