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L7224A,C; L7248A,C,L OIL AND ELECTRIC BOILER ELECTRONIC AQUASTAT
Table 4. Display readout definitions.
Text
Description
Error Code (if one is present)
Err
Boiler Temperature
bT
1
HL
High Limit
High Limit Differential
HdF
Low Limit (L7224 only)
LL
Low Limit Differential (L7224 only)
Ldf
Local Thermostat Status
tt
EnviraCOM Thermostat Status
ttE
B1 (Burner) output (ON or OFF)
brn
C1 (Circulator) output (ON or OFF)
Cir
ZC (Zone Control) output (ON or OFF)
ZC
ZR (Zone Request) Call for HEAT (ON or OFF)
Zr
External Low Limit Enabled (L7248L only)
ELL
ZR Configured as Domestic Hot Water
duu
Request (L7224, L7248L only)
Anti Short-Cycle Timeout
ASC
2
bSP
Boiler Set-Point
dhc
DHW Module Connected
ot
Outdoor Temperature
otL
Outdoor Temperature Low
otH
Outdoor Temperature High
btL
Boiler Temperature Low
2
bP
Boost Period
2
bS
Boost Step
UUS
Warm Weather Shutdown Temperature
1
Display shows local setting; not the setting as modified by an
external enviracom control.
2
Settings are viewable only if the outdoor reset module and out-
door temperature sensor are installed and functioning properly.
3
Settings are viewable only if the domestic hot water module
and sensor are installed and functioning properly.
Operation
The L7224 and L7248 models can be in any of four
operational states: Normal, High Limit, Low Limit and
Error. The controller moves back and forth from
High Limit to Normal to Low Limit state as part of
normal operation. Only devices having High Limit
settings are restricted to the High Limit and Normal
states. However, the controller will enter the Error state
when there is an abnormal condition. The operating
states are:
1. Normal: Boiler temperature went below the High
Limit setting (minus the Differential) and has
not exceeded the High Limit setting; or, the
boiler temperature went above the Low Limit
68-0281EFS—09
Display
3
(YES or NO)
2
2
2
2
2
®
setting and has not gone below the Low Limit
setting (minus the Differential); or, ZR input is
not powered with 120 Vac (only L7248L with
ELL set On).
2. High Limit: Boiler temperature went above the
High Limit setting and has not dropped below
the High Limit setting (minus the Differential).
3. Low Limit: Boiler temperature went below the
Low Limit setting (minus the Low Limit Differen-
tial) and has not gone above the Low Limit set-
ting; or, ZR input is powered with 120 Vac (only
L7248L with ELL set On).
4. Error: The controller has detected an error condi-
tion (e.g., open sensor) and has shut down the
burner output. The ZC output is energized. The
controller continues to monitor the system and
automatically restarts if the error condition
clears. Refer toTable 4.
The operating sequence for the L7224/L7248 is
shown in
Table 6–9.
High Limit Controller
The High Limit opens and turns off the burner when
the water temperature reaches the setpoint. The High
Limit automatically resets after the water temperature
drops past the setpoint and through the Differential.
The L7248 models have High Limit Differential
presets of 15 °F (8 °C). The L7224 models have High
Limit Differential presets of 10 °F (6 °C).
Low Limit and Circulator
Controller
On a temperature rise, with the adjustable Differential
at the default setting of 10 °F (6 °C), the burner circuit
breaks and the circulator circuit makes (assuming no
call for heat is present) at the Low Limit setpoint. On a
temperature drop of 10 °F (6 °C) below the Low Limit
setpoint, the burner circuit makes and the circulator
circuit breaks. See Fig. 7.
HIGH LIMIT
SETTING
L7224: 10°F (6°C)
DIFFERENCE
L7248: 15°F (8°C)
DIFFERENCE
LOW LIMIT
SETTING
10ºF (6ºC)
DIFFERENCE
WHEN WATER REACHES LOW LIMIT SETTING, THE BURNER SHUTS
1
OFF OR THE CIRCULATOR PUMP STARTS (WHEN CALLING FOR HEAT).
Fig. 7. Setpoints and differentials.
Anti Short-Cycle Feature
The Anti Short-Cycle feature allows for field selection
of a delay time between burner cycles. Should a call
for heat occur following the end of the previous heat
cycle and before the Anti Short-Cycle delay time is
6
CONTROLLERS
SWITCH BREAKS ON
TEMPERATURE RISE.
BURNER TURNS OFF.
CIRCULATOR OPERATES
ON A CALL FOR HEAT.
SWITCH MAKES ON
TEMPERATURE FALL.
BURNER OPERATES ON A
CALL FOR HEAT.
WITH NO HEATING
DEMAND, SWITCH BREAKS
ON TEMPERATURE RISE.
SWITCH MAKES ON
TEMPERATURE FALL,
BURNER IS ON TO
MAINTAIN MINIMUM
WATER TEMPERATURE.
CIRCULATOR IS OFF.
1
M23364
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