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Honeywell L7224A Installation Instructions Manual page 6

Oil and electric boiler
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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
bT
Boiler Temperature
HL
1
High Limit
HdF
High Limit Differential
LL
Low Limit (L7224 only)
Low Limit Differential (L7224 only)
Ldf
tt
Local Thermostat Status
EnviraCOM Thermostat Status
ttE
B1 (Burner) output (ON or OFF)
brn
Cir
C1 (Circulator) output (ON or OFF)
ZC (Zone Control) output (ON or OFF)
ZC
Zr
ZR (Zone Request) Call for HEAT (ON or OFF)
ELL
External Low Limit Enabled (L7248L only)
ZR Configured as Domestic Hot Water
duu
Request (L7224, L7248L only)
Anti Short-Cycle Timeout
ASC
bSP
2
Boiler Set-Point
dhc
DHW Module Connected
ot
Outdoor Temperature
otL
Outdoor Temperature Low
otH
Outdoor Temperature High
btL
Boiler Temperature Low
bP
2
Boost Period
bS
2
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 setting and
68-0281EFS—07
Display

















3
(YES or NO)

2

2

2

2



2
®
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 Differential) and
has not gone above the Low Limit setting; or, ZR
input is powered with 120 Vac (only L7248L with
ELL set On).
4. Error: The controller has detected an error condition
(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
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.
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 expired, the
circulator will be allowed to run, but the burner will be held
off until the time has elapsed. The range of the Anti Short-
Cycle time is from OFF to five minutes.
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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