L7224U OIL ELECTRONIC AQUASTAT
®
CONTROLLER
69-1720—03
8
Table 3. L7224/L7248 Controller Operating Sequence.
* Error condition only available when the Outdoor Reset
Module is installed.
Action
System Response
Thermostat
calls for heat.
Circulator starts when water temperature is
above Low Limit setting (if applicable).
Boiler temperature is checked. Burner
starts when water temperature is below
High Limit setting.
If Anti-short Cycle Time is enabled, the
burner does not start until the set Anti-
short Cycle Time between cycles expires
after the previous call for heat was
satisfied.
Boiler
temperature
exceeds the
High Limit.
Burner is turned off. Burner restarts when
the water temperature drops below the
High Limit setting minus the Differential.
Thermostat is
satisfied.
Circulator and burner turn off.
Boiler
temperature
drops below
the Low Limit
setting minus
the
differential (if
applicable).
Burner is turned on, Circulator is turned
off. Burner stops when the water
temperature exceeds the Low Limit
setting.
Error
conditions
1-5.
If an error condition is detected, all outputs
except ZC are shut down. Burner is off.
The controller continues to function and
restarts when error is corrected.
During the error check sequence, the
system checks for drift in the sensor and
corrosion in the connections.
Error
condition 6.
EnviraCOM communication is not
available.
Error
condition 7.
The controller has reset the High Limit,
Low Limit and Differential Setting to a
default setting and will continue to run at
those settings. Performance of the system
will be degraded.
Error
condition 8.
If the error condition is detected, all
outputs except ZC are shut down. Burner
is off.The controller continues to function
and restarts when all three user keys have
been pressed longer than 60 seconds.
Error
condition 9*.
System continues to run with no outdoor
reset functionality
Error
condition 10*.
System continues to run with outdoor reset
parameters enabled as programmed.
Error cleared automatically.
Error
condition 11*.
System continues to run with boiler temp
set to High Limit.
Table 4. L7224 Controller Operating Sequence with
multiple zones connected through the ZR terminal
Action
System Response
Zone Request (ZR)
terminal is
connected to L1
(Zone calls for
heat).
Boiler temperature is checked.
Burner starts when water
temperature is below High Limit
setting. Anti Short-Cycle Time is
applied, see Table 3.
Boiler temperature
exceeds the High
Limit.
Burner is turned off. Burner restarts
when the water temperature drops
below the High Limit setting minus
the Differential.
Zone Request input
is de-energized
(Zones are
satisfied).
Burner turns off.
Boiler temperature
drops below the
Low Limit setting
minus the
differential (if
applicable).
Burner turns on and Zone Control
is de-energized. Burner turns off
and Zone Control is re-energized
when the water temperature
exceeds the Low Limit setting.
Table 5. Controller Operating Sequence with External
Low Limit device connected trough the ZR terminal.
Action
System Response
Zone Request (ZR)
terminal is
connected to L1
(External Low Limit
call for heat).
Boiler temperature is checked.
Burner starts when water
temperature is below High Limit
setting. Circulator turns off.
Boiler temperature
exceeds the High
Limit.
Burner is turned off. Burner restarts
when the water temperature drops
below the High Limit setting minus
the Differential.
Zone Request input
is de-energized
(External Low Limit
is satisfied).
Burner is turned off.
Table 6. L7224 Controller Operating Sequence with
Domestic Hot Water connected trough the ZR
terminal.
Action
System Response
Zone Request (ZR)
terminal is connected to
L1 (Domestic Hot Water
calls for heat).
Boiler temperature is checked.
Burner starts when water
temperature is below High
Limit setting.
Boiler temperature
exceeds the High Limit.
Burner is turned off. Burner
restarts when the water
temperature drops below the
High Limit setting minus the
Differential.
Zone Request input is
de-energized (Domestic
Hot Water is satisfied).
Burner is turned off.
