Laars Mascot II, Инструкция по установке и эксплуатации

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LAARS Heating Systems
Page 30
SECTION 9.
Modes of Operation
The Mascot II 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 Mascot II 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 Mascot II 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, shifts the 3-way valve
position 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 Mascot II enters "run". If the
flame signal is below the threshold the Mascot II returns
to prepurge and starts the ignition process over. In "run"
the Mascot II 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 24 . 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 Using External
Modulation Control
When using the Mascot II for hydronic heating
with external modulation control a call for heat must be
supplied to the "T-T" terminal. Once the call is supplied
the control starts the boiler and system pumps and
begins the ignition process. In "run" the Mascot II
NAME FUNCTION DEFAULT VALUE
CH on Burner demand begins when the 5°F
differential outlet water temperature reaches
"Outlet water temperature setpoint"
minus "CH on differential"
CH off Burner demand ends when the 5°F
differential outlet water temperature reaches
"Outlet water temperature setpoint"
plus "CH off differential"
DHW on Burner demand begins when the 2°F
differential outlet water temperature reaches
"Outlet water temperature setpoint"
minus "DHW on differential"
DHW off Burner demand ends when the 7°F
differential outlet water temperature reaches
"Outlet water temperature setpoint"
plus "DHW off differential"
Pump Operates the pump for the overrun 1
overrun time after the burner demand minute
has ended
High Locks the boiler out when the high 200°F
limit limit temperature is reached
(requires manual reset)
Flame Flame signals lower than the flame 0.8Vdc
threshold threshold interrupt burner operation
Table 12. Default Control Settings.