Honeywell Aquasat L7224 A Aquasat L7224 C Manual page 10

L7224A,C; L7248A,C,L OIL AND ELECTRIC BOILER
Table 7. L7224/L7248 Controller Operating Sequence with multiple zones connected through the ZR ter-
Action
Zone Request (ZR) terminal is connected to
L1 (Zone calls for heat).
Boiler temperature exceeds the High Limit. Burner is turned off. Burner restarts when the water temperature
Zone Request input is de-energized (Zones
are satisfied).
Boiler temperature drops below the Low
Limit setting minus the differential (if
applicable).
.
Table 8. Controller Operating Sequence with External Low Limit device connected trough the ZR terminal.
Action
Zone Request (ZR) terminal is connected to
L1 (External Low Limit call for heat).
Boiler temperature exceeds the High Limit. Burner is turned off. Burner restarts when the water temperature
Zone Request input is de-energized
(External Low Limit is satisfied).
Table 9. L7224 Controller Operating Sequence with Domestic Hot Water connected trough the ZR terminal.
Action
Zone Request (ZR) terminal is connected to
L1 (Domestic Hot Water calls for heat).
Boiler temperature exceeds the High Limit. Burner is turned off. Burner restarts when the water temperature
Zone Request input is de-energized
(Domestic Hot Water is satisfied).
68-0281—18
minal.
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.
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.
Burner turns off.
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.
Boiler temperature is checked. Burner starts when water
temperature is below High Limit setting. Circulator turns off.
drops below the High Limit setting minus the Differential.
Burner is turned off.
Boiler temperature is checked. Burner starts when water
temperature is below High Limit setting.
drops below the High Limit setting minus the Differential.
Burner is turned off.
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System Response
System Response
System Response