L7224U OIL ELECTRONIC AQUASTAT
®
CONTROLLER
69-1720—03
6
Fig. 7. Explanation of display readout.
*Settings viewable on the 3-digit display only if the
“Outdoor Reset Module” is installed.
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 Dif-
ferential).
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.
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 4–6.
The operating sequence for the L7224U is shown in Table
3.
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.
Fig. 8. Setpoints and differentials.
Boiler Temperature
Description
Display
Shows
High Limit Differential
Low Limit (L7224 only)
Low Limit Differential (L7224 only)
Local Thermostat Status
EnviraCOM Thermostat Status
Boost Step
Warm Weather Shutdown Temperature
M29552
ZR Configured as Domestic Hot Water
Request (L7224, L7248L only)
Anti Short-Cycle Timeout
Outdoor Temperature Low
Outdoor Temperature High
Boiler Temperature Low
Boost Period
DISPLAY SHOWS LOCAL SETTING; NOT THE SETTING
AS MODIFIED BY AN EXTERNAL ENVIRACOM CONTROL.
SETTINGS ARE VIEWABLE ONLY IF THE OUTDOOR
RESET MODULE AND OUTDOOR TEMPERATURE
SENSOR ARE INSTALLED AND FUNCTIONING PROPERLY.
SETTINGS ARE VIEWABLE ONLY IF THE DOMESTIC
HOT WATER MODULE AND SENSOR ARE INSTALLED
AND FUNCTIONING PROPERLY.
1
2
3
Text
bt
HdF
LL
Ldf
tt
ttE
External Low Limit Enabled (L7248L only)
ELL
B1 (Burner) output (ON or OFF)
C1 (Circulator) output (ON or OFF)
ZR (Zone Request) Call for HEAT (ON or OFF)
ZC (Zone Control) output (ON or OFF)
brn
Cir
ZC
Zr
duu
ASC
otL
otH
btL
bP
bS
UUS
2
2
2
2
Input or Output is OFF
Input or Output is ON
Units are displayed in degrees Fahrenheit
Units are displayed in degrees Celsius
°F
°C
OFF
On
2
2
Outdoor Temperature
ot
2
DHW Module Connected (YES or NO)
dhc
3
2
Boiler Setpoint
bSP
High Limit
HL
1
Error Code (if one is present)
Err
LOW LIMIT
SETTING
HIGH LIMIT
SETTING
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.
M23365
WHEN WATER REACHES LOW LIMIT SETTING, THE BURNER SHUTS
OFF OR THE CIRCULATOR PUMP STARTS (WHEN CALLING FOR HEAT).
1
1
10ºF (6ºC)
DIFFERENCE
10ºF (6ºC)
DIFFERENCE
