L7224 Series
Oil Electronic
Aquastat® Controller
TECHNICIAN’S QUICK REFERENCE GUIDE
The following service procedure provides a quick overview for
L7224 Series Controllers. For more information, refer to form
69-1384.
On the L7224U the High Limit, High Limit Differential, Low Limit,
and Low Limit Differential can be adjusted to the settings
recommended by the boiler OEM.
Adjusting Settings
To discourage unauthorized changing of Aquastat® settings, a
procedure to enter the adjustment mode is required. To enter the
adjustment mode, press the UP, DOWN, and I buttons
simultaneously for three seconds. Press the I button until the
feature requiring adjustment is displayed:
•
•
•
•
HL—High Limit.
LL—Low Limit.
Ldf—Low Limit differential.
F - C—°F or °C.
Then press the UP and/or DOWN buttons to move the set point to
the desired value. After 60 seconds without any button inputs, the
control will automatically return to the READ mode.
To use the L7224U in a cold start boiler application, disable the
Low Limit function by pressing the UP arrow button, DOWN arrow
button and I buttons simultaneously for three seconds. Then push
the I button until LL is displayed. Then press the down arrow
button until OFF is displayed.
Display
In the RUN mode, the Aquastat® will flash “bt” (boiler temp)
followed by the temperature (i.e., 220), followed by °F or °C.
To read boiler settings, press the I key to read the parameter of
interest. For example, press I (HL) High Limit is displayed,
followed by a three-digit number, i.e., 220, followed by °F or °C.
69-1957—1
L7224 SERIES
Table 2. L7224 Controller Operating Sequence
Action
System Response
Thermostat
Circulator starts when water temperature is
calls for heat. above Low Limit setting (if applicable). Boiler
temperature is checked. Burner starts when
water temperature is below High Limit setting.
Boiler exceeds Burner is turned off. Burner restarts when the
the High Limit. water temperature drops below the High Limit
setting minus the differential.
Thermostat is Circulator and burner turn off.
satisfied.
Error conditions If an error condition is detected, all outputs
1-5.
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 conditions If error condition 6 or 7 occurs, the control has
6-7.
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 If the error condition is detected, all outputs
8.
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.
Troubleshooting
When attempting to diagnose system performance, reference the
LED display to help identify specific areas not working properly.
The LED display will scroll “err”, followed by a digit (1-8). See
Table 1 for a description of the error and suggested actions. See
below for a troubleshooting guide.
Table 3. Troubleshooting Guidea.
System
Condition Condition
Diagnostic
Check
Action
Boiler is Display is OFF 120 Vac system Turn system power on.
cold,
house is
cold
power.
Display is ON; 24 Vac T-T
TT-LED is OFF
No 24V; replace
control
Display is ON; 24V present;
TT-LED is OFF disconnect
thermostat,
Boiler starts, check
wiring and thermostat
short T-T
a
.Refer to Fig. 5 for Display and LED locations.
.ZC LED ON indicates ZC terminal power is OFF.
b
c
. ZC LED OFF indicates ZC terminal power is ON.
3
69-1957—1
Table 3. Troubleshooting Guidea.
Diagnostic
System
Condition Condition
Check
Action
Boiler is Display is ON; 120 Vac at B1- • If no, replace control.
cold,
TT-LED is ON B2
• If yes, check burner
and wiring
—
house is B1 LED is ON
cold
Display is ON; Refer to err on
TT-LED is ON display
Boiler is Display is ON; 120 Vac at C1- • 120 Vac at C1-C2,
hot, house TT-LED is ON C2
check wiring to pump
• Wiring ok, is pump
running? If not,
is cold
C1 LED is ON
replace the pump.
• If pump is running,
check for trapped air
or closed zone
valves.
Display is ON; Boiler below the
TT-LED is ON Low Limit
C1 LED is OFF; temperature,
ZC LED is ONb
wait for boiler to
go above Low
Limit
temperature.
Display is ON; Boiler above
• If no 120 Vac,
replace control.
• If yes, check zone
relays, circulators
and wiring.
TT-LED is ON LL? If yes,
ZC LED is
check for 120
Vac between ZC
and L2
OFFc
a
.Refer to Fig. 5 for Display and LED locations.
.ZC LED ON indicates ZC terminal power is OFF.
b
c
. ZC LED OFF indicates ZC terminal power is ON.
Automation and Control Solutions
Honeywell International Inc.
1985 Douglas Drive North
Golden Valley, MN 55422
customer.honeywell.com
Honeywell Limited-Honeywell Limitée
35 Dynamic Drive
Toronto, Ontario M1V 4Z9
® U.S. Registered Trademark
© 2006 Honeywell International Inc.
69-1957—1 Rev. 06-06
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