L7224A,C; L7248A,C,L OIL AND ELECTRIC BOILER ELECTRONIC AQUASTAT
®
CONTROLLERS
9
68-0281EFS—07
* Error condition only available when the Outdoor Reset Module is installed.
Table 6. L7224/L7248 Controller Operating Sequence.
Action
System Response
Thermostat calls for heat.
Circulator starts when water temperature is above Low Limit setting (if
applicable) or above the Thermal Purge Temperature Limit (tPL) if
Thermal Purge is enabled. Boiler temperature is checked. Burner
starts when water temperature is below High Limit setting minus the
differential or at or below the Thermal Purge Temperature Limit (tPL)
for cold start boilers if the Thermal Purge Temperature Limit is
enabled. If tPL is enabled, the burner may also start if the boiler
temperature is cooling at 10 ºF or greater per minute or the Thermal
Purge Time Delay (tPt) has expired.
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. If Thermal
Purge is enabled, the burner is turned on when either the Thermal
Purge Temperature Limit is reached, the Thermal Purge Time Delay
has expired or the boiler temperature cooling rate exceeds 10 ºF/
minute.
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. Power to Zc is
removed.
Error condition
1-5.
If an error condition is detected, all outputs except ZC are shut down.
Burner is off. Control 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 control 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. Control 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 7. L7224/L7248 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 or at or below the Thermal Purge
Temperature Limit (tPL) for cold start boilers if the Thermal Purge
Temperature Limit is enabled. If tPL is enabled, the burner may also
start if the boiler temperature is cooling at 10 ºF or greater per minute
or the Thermal Purge Time Delay (tPt) has expired. Anti Short-Cycle
Time is applied, see Table 6.
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. If Thermal
Purge is enabled, the burner is turned on when either the Thermal
Purge Temperature Limit is reached, the Thermal Purge Time Delay
has expired or the boiler temperature cooling rate exceeds 10 ºF/
minute.
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.
