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L7224U OIL AND ELECTRIC BOILER ELECTRONIC AQUASTAT
Table 3. 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 set-point (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)
duu
ZR Configured as Domestic Hot Water
Request (L7224, L7248L only)
ASC
Anti Short-Cycle Timeout
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 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 boiler tem-
perature 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).
69-1720EFS—13
Display
3
(YES or NO)
2
2
2
2
2
®
CONTROLLER
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.
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
10ºF (6ºC)
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.
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.
Anti Short-Cycle Feature
The Anti Short-Cycle feature allows for field selection of
a minimum 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.
NOTE:
The Anti Short-Cycle feature is blocked if DHW
demand occurs. DHW demands are serviced
immediately, without any delay.
6
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.
1
SWITCH MAKES ON
TEMPERATURE FALL,
BURNER IS ON TO
MAINTAIN MINIMUM
WATER TEMPERATURE.
CIRCULATOR IS OFF.
M23365
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