LAARS NeoTherm NTV600 - Install and Operating Manual - Manual (Page 42)

LAARS Heating Systems
Page 40
SECTION 9.
Modes of Operation
The NeoTherm control allows the boiler to operate
in many different modes of operation. The mode must
be selected based upon the requirements of the
installation. The following sections describe the basic
operation of the NeoTherm in each of the different
modes. Familiarize yourself with each mode and how
the operation of the boiler varies, depending upon the
installation and inputs the control is monitoring.
9.1 Hydronic Heating Demand
When using the NeoTherm for hydronic heating a
call for heat must be supplied to the "T-T or Interlock"
terminal. Once the call is supplied the control starts the
boiler and system pumps and begins the ignition
process. The ignition process consists of a prepurge,
trial for ignition, and run period. The prepurge period
starts on a call for heat once the fan RPM reaches a
preset level. The trial for ignition period follows once
the start-up RPM of the fan is reached. The trial for
ignition period lasts 4 seconds during which the direct
spark ignition system and gas valve are energized. At
the end of the trial for ignition period the flame signal is
compared with the preset flame threshold value. If the
flame signal is higher than the flame threshold the
NeoTherm enters "run". If the flame signal is below the
threshold the NeoTherm returns to prepurge and starts
the ignition process over. In "run" the NeoTherm
monitors the flame signal, call for heat, safeties, and
water temperatures and modulates as needed between
100% and 20% of rate to satisfy the call for heat.
9.2 Hydronic Heating with Outdoor Reset
Outdoor reset varies the control point setpoint
based on the actual outdoor temperature. The reset
function works as shown in
Figure 32 . When the
outdoor air temperature reaches the "high outdoor
temperature setpoint (HOD), the control point setting is
adjusted to the low boiler temperature setpoint (LBT).
When the outdoor air temperature reaches the low
outdoor temperature setpoint (LOD), the control
setpoint is adjusted to the CH/Outlet water setpoint
temperature. HOD, LOD and LBT can be adjusted by
accessing SETUP mode. CH setpoint is adjustable from
the USER menu structure.
9.3 Hydronic Heating with Domestic Hot
Water (DHW) Priority
When using the NeoTherm for hydronic heating
with domestic hot water priority a call for heat must be
supplied to the "T-T or Interlock" terminal. Once the
call is supplied the control starts the boiler and system
pumps and begins the ignition process. The ignition
process consists of a prepurge, trial for ignition, and run
period. The pre-purge period starts on a call for heat
once the fan RPM reaches a preset level. The trial for
ignition period follows once the start-up RPM of the fan
is reached. The trial for ignition period lasts 4 seconds
during which, the direct spark ignition system and gas
valve are energized. At the end of the trial for ignition
period the flame signal is compared with the preset
flame threshold value. If the flame signal is higher than
the flame threshold the NeoTherm enters "run". If the
flame signal is below the threshold the NeoTherm
returns to pre-purge and starts the ignition process over.
In "run" the NeoTherm monitors the flame signal, call
for heat, safeties, and water temperatures modulating as
needed between 100% and 20% of rate to satisfy the call
for heat. When a DHW demand is applied during a
hydronic call for heat the priority feature forces the
boiler to switch to the DHW demand for the priority
time. The DHW priority demand forces the control to
operate to the DHW setpoint, de-energizes the system
pump and energizes the DHW pump.
9.4 Hydronic Heating Using External
Modulation Control
When using the NeoTherm for hydronic heating
with external modulation control a call for heat must be
supplied to the "T-T or Interlock" terminal. Once the
call is supplied the control starts the boiler and system
pumps and begins the ignition process. The ignition
process consists of a prepurge, trial for ignition, and run
period. The prepurge period starts on a call for heat
once the fan RPM reaches a preset level. The trial for
ignition period follows once the start-up RPM of the fan
is reached. The trial for ignition period lasts 4 seconds
during which the direct spark ignition system and gas
valve are energized. At the end of the trial for ignition
period the flame signal is compared with the preset
flame threshold value. If the flame signal is higher than
the flame threshold the NeoTherm enters "run". If the
flame signal is below the threshold the NeoTherm
returns to prepurge and starts the ignition process over.
In "run" the NeoTherm monitors the flame signal, call
for heat, safeties, and water temperatures. The boiler
Figure 32. Outdoor Reset Setpoint Temperatures.