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L7224U OIL AND ELECTRIC BOILER ELECTRONIC AQUASTAT
After approximately 60 seconds without any key
presses, the display will enter a dim display mode. To
return to the bright display mode, simply press and
release any key.
Table 3. 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 set-point (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
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 L7224U 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.
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
69-1720EFS—11
Displa
3
(YES or NO)
2
2
2
2
2
®
CONTROLLER
boiler temperature went above the Low Limit
setting and has not gone below the Low Limit
setting (minus the Differential).
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-
y
ting.
4. Error: The controller has detected an error
condition (e.g., open sensor) and has shut down
the burner output. The Zone Control (ZC) output
is energized. The controller continues to monitor
the system and automatically restarts if the error
condition clears. Refer to Table 6–8.
The operating sequence for the L7224U is shown in
Table 5.
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 adjustable
Differential.
Low Limit and Circulator Controller
On a temperature rise, 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 (with the adjustable Differential at the
minimum setting of 10 °F
(6 °C)), the burner circuit makes and the circulator
circuit breaks. Refer to Fig. 7.
HIGH LIMIT
SETTING
LOW LIMIT
SETTING
1
WHEN WATER REACHES LOW LIMIT SETTING, THE BURNER SHUTS
OFF OR THE CIRCULATOR PUMP STARTS (WHEN CALLING FOR HEAT).
Fig. 7. Setpoints and differentials.
NOTE: Setting the Low Limit above the High Limit
less the High Limit Differential is not allowed
as improper circulator and Zone Control
functions could result.
6
SWITCH BREAKS ON
TEMPERATURE RISE.
BURNER TURNS OFF.
CIRCULATOR OPERATES
ON A CALL FOR HEAT.
10ºF (6ºC)
SWITCH MAKES ON
DIFFERENCE
TEMPERATURE FALL.
BURNER OPERATES ON A
CALL FOR HEAT.
WITH NO HEATING
DEMAND, SWITCH BREAKS
10ºF (6ºC)
ON TEMPERATURE RISE.
DIFFERENCE
SWITCH MAKES ON
TEMPERATURE FALL,
BURNER IS ON TO
MAINTAIN MINIMUM
WATER TEMPERATURE.
CIRCULATOR IS OFF.
1
M23365
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