Honeywell Boiler L7224 User Manual

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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